soil erosion problems 
on an a~isol in 
western nigeria 
and their cOltrol 
by 
R.Lol 
liTA  MONOGRAPH NO.l 
soil erosion problems 
on an aifisol in 
western niger~a 
and their control 
by 
R. Lal 
II TA  MONOGRAPH NO. 1 
APPROVED FOR PUBLICA nON 
(MAY. 1975} 
1st Published 19'76 
Reprinted 1979 
Table of Contentl 
Li st of Illustrations (plates).. •• .. •• vi 
List of Illustrations (Figures) •• •• .. " vii 
Li st of Tables.. •• xi 
List of Appendices .. ,. .. .. .. .. .. .. xv 
Foreword.. .. .. .. •• .. •• ., .. .. •• .. .. xvi i 
Acknowledgements .• .. .. .. .. •• .. .. xix 
Introduction.. .. .. .. .. .. .. ....,' 1 
Runoff plots: location, Design and Construction 3 
Resul ts of the Preliminary Experiments .. " .. 11 
Treatments .. .. .. .. .. •. •• .. .. .. .. .. .15 
Rainfall characteri sties.. .. .• •• .. .. .. 19 
Soi I and water losses for different slopes and 
soil management practi ces .. .. .. .. .. •. .. 25 
Mulching effects on runoff and soil loss ...... .. ·41 
. Rainfall erosivity and soil erosion.. .. .• " .. 53 
Effect of slope I ength on runoff and soi I loss .. 71 
Nutrient loss in water runoff .. .... .. .. .. .. 77 
Nutrient Joss in eroded sediments '" .. .. 95 
Properties of the eroded sediments in relation to 
the original. soi I ........ . .. •• .. .• .. 107 
- Changes in soil physical dlaracteristics and crop yield 
as a result of erosion .. .. •• •• ' .. 117 ' 
lIlt of IIlu/tratlonl (Plate/) 
Plate 1.1 
Runoff plot construction and collection equipment: 
(a) Collection system with apron and sill installed 
toward the lower md of the plot. In the bottom 
right hand si de in the upper portion is the Neutron 
Probe Access Tube .............. .. 5 
(b) Bare fallow plot with complete runoff collection 
system. In the center of the plot is a non-recording 
rai n gauge ..~................. 5 
(c) Close up of the flume, a 900 V-notch, still well and 
water level recorder .. .. .. •• .. .. .. .. 6 
(d) Sedimentation and storage tank with two screens 
and a di vi sor system in the last compartmen t.. .. 6 
(e) Multi-divisor system and an over-flow tank. .• .. 7 
(f) A complete over·view of the retaining wall, trench 
and collection system. 7 
(g) An over-all view of the crops being grown in the 
runoff plots .. •• •• .. .. .. •• •• .. .. 8 
Fig.l.a Relationship of rainfall distr i bution wi th soil 
erosion hazard in West Africa. 1 
Fig.l.' The approximate locations of runoff plots of 
di fferent slopes along a topo sequence. 3 
Fig.5.l Rainfall intensity distribution of storms from 
1972 to 1974. 20 
Fig.S.2 Rainfall intensity distribution during a stann 
with the peak intensity occurring in its beginning. 21 
Fig.5.3 A storm with a low initial intensity and a sec-
ond peak immediately following a high peak. 22 
Fig.5.4 A composite storm with two separate intensity 
peaks spaced widely apart. 22 
Fig.6.l Influence of soil management crop rotations 
and slope on soil erosion in 1972. Note that 
V-axis is a log scale. 32 
Fig.6.2 Influence of soil management crup rotations 
and slope on soi I erosion in 1973. Note that 
V-axis is a log scale. 33 
Fig.7.1 Effects of mulch rate, no-tillage system and 
slope on soil erosion in the first season, 1974. 45 
Fig.7.2 Effects of mulch rale, no-tillage system and 
slope on soi I erosion in the second season, 1974 46 
Fig.7.3 Mulch factor for runoff and soil erosion. 48 
Fig.7.4 Influence of degree of slope on mulch factor 
for soi I erosion under different mul ch rates and 
no-tillage system. 49 
Fig.8.l Cumulative distribution of erosivity index Aim 
from Ibadan. If one does not divide the R.H.S. 
of Almequation, the numerical value of Aim 
(cm 2! hr) and EI30 (foot-tons per acre-inch) are 
i denti cal. Hence it does not matter how is K 
factor computed either by Aim or E130. 64 
viii Soil erosion problems on an al/isol ;n Western Nigeria 
Fig.a.l An hypothetical iso-erodent map for West Africa. 65 
Fig.8.3 Cumulative distribution of El30 index for Ibadan 65 
Fig.8.4 Monthly distribution of EI30 index for Ibadan. 66 
Fig:a.5 Relationship between (EI30/100) in foot-toni 
acre and Aim (cm2/hr) for individual storm. 66 
Fig.8.6 Changes in soil erodibility factor(K) with time 
after forest clearing. 68 
Fig.9.1 Slope characteristics and slope length of runoff 
plots at 10 and 15 percent slopes. 72 
Fig.10.1 Effects of slopes, crop rotations and residue 
management on loss of total nutri ent el ements i n 
runoff water in 1972. 79 
Fig.1O.2 Effects of slopes, crop rotations and residue 
management on loss of total nutrient elements in 
runoff water in 1973. 80 
Fig.l0.3 Loss of N03-N in runoffwater atdifferent stages 
of crop growth as influenced by soil manage-
ment and crop rotation treatrrents. 85 
Fig.l0.4 Loss of nutrient elements such as P,K, Ca and 
Mg in water runoff at different stages of crop 
growth. 85 
Fig.10.S Relative nutrient concentration in runoff water 
from different treatments of soil management 
and crop rotation. 86 
Fig.10.6 Relative nutrient concentration in surface runoff 
and sub-surface inter-flow water. 87 
Fig.l0.7 Changes in the concentration of NOJ-N, P and K 
at different times after ferti lizer application. 89 
Fig.10.8 The effects of different mulch rates and slopes 
on total nutrient elements loss in runoff water. 90 
Fig.n.l Effects of slopes and crop rotations on total 
nutri ent loss in eroded sediments during 1972. 96 
Fig.1l.2 Total loss of organic carbon in the eroded sedi-
ments in 1972. 97 
Fig.11.3 Total loss of organic carbon in the eroded sedi-
ments in 1973. 97 
Fig.11.4 Effect of mulch rates on total loss of organiC 
carton in the eroded sediments in the fi rst 
season, 1974. 103 
List of Illustrations (Figures) lX 
Fig.l1.5 Effect of mulch rates on total loss of organic 
carron in the eroded sediments in the second 
season, 1974. 103 
Fig.12.1 Changes in the textural composition of surface 
soil from 1972-1974 as compared to that of the 
eroded sediments. 108 
Fig.12.2 Influence of soil slope on concentration of 
gravel s, sand, si It and cl ay in the eroded sedi-
ments. 109 
Fig.12. 3 Soil moisture retention characteristics of eroded 
soi I as compared wi th that of surface soi I sam-
ples obtai ned from the rune ff plots. 110 
Fig. 12.4 Changes in the enri chment ratio of organi c car-
bon and total nitrogen with time. 111 
Fig.12.5 Effects of soil slope on the enrichment ratio of 
some nutrient elements. t 12 
Fig.B.1 Infiltration capacity of the soil as influenced by 
time after forest clearing under different soil 
management and crop rotation treatments. 118 
Fig.13.2 Changes in texture of the soil in bare fallow 
plots during 1972-1973. 119 
Fig.13.3 Soi I moisture retention characteri sties as in­
fluenced by soi I managertEnt and crop rotation 
treatments. 121 
Fig.13.4 Relative maize yield during 1972 and 1973. 122 
fig.13.S The influence of artificial soil removal on yield 
response of maize (Zea mays l.) and cowpeas 
(Vigna unguicuJata). 123 
I. t ~ . ~ 
, J~ o~ 
Tabl e 2.1 Slope characteristics of each run-off plots. 4 
Tabl e 3.1 Effect of crop cover and mulching on run-off 
(an), September - December, 1970. Total 
Rainfall .. 29.5 em. 11 
Table 3.2 Relative Soil loss under Different Vegeta-
tion and Crop Cover (Relative to Natural 
Vegetation plot of 1% slope). 11 
Table 3.3 Particl e size distribution of the composite 
samples of the eroded sediments. 12 
Table 3.4 Nutrient Concentration in the runoff water 
(ppm)(Average of two rain storms). 12 
Table 3.5 Total nutrient loss in run-off water (kg/Ita! 
season). 12 
Table 3.6 Nutrient contents of the composite sample 
from eroded sediments (ppm). 13 
Tabl e 4. T Soil and crop management treatments for 
1972-73. 15 
Table 4.2 Treatment allocation to run-off plots for 
1972-73. 16 
Table 4.3 Treatment allocation for 1974. 17 
Tabl e 6.1 Effect of slope and soi I management on 
run-off loss (mm). First season 1972. 26 
Tabl e 6.2 Effect of slope and soil management on 
run-off loss (mm). Second season 1972. 26 
Table 6.3 Effect of slope and soil management on 
run-off los s (mm). Fi rst season 1973. 26 
Table 6.4 Effect of slope and soil management on 
run-off los s (mm). Second season' 973. 26 
Table 6.5 Run-off slope relations 1972. 27 
Table 6.6 Run-off slope relations 1973. 27 
Table 6.7 Run-off slope relations 1972 28 
Table 6.8 Run-off slope relations 1973 28 
Tabl e 6.9 Slope run-off relations for each season for 
maize-co~ea (no-tillage) and cowpea-
maize(plowed) treatments. 29 
List of Illustrations (Tables) Xl 
Table 6.10 Crop and soi I management facto r. 30 
Table 6.11 Crop and soil management factor for dif-
ferent stages of growth (based on 1973 
records) 30 
Table 6.12 Effect of slope and soi I management on 
soil loss (tons/ha). First season 1972. 31 
Table 6.13 Effect of slope and soil management on 
soil loss (tons/ha). Second season 1972. ·31 
Table 6.14 Effect of slope and soil management on 
soil loss (tons/ha). First season, 1973. 31 
Table &.15 Effect of slope and soil management on 
soil loss (tons/ha). Second season, 1973. 31 
Table 6.16 Multiple regression of soil loss with slope, 
1972. 34 
Table 6.17 Soil -loss-slope relationships, 1973. 35 
Table 6.18 Soil loss-slope relationships, '972. 35 
Table 6.19 Soil loss-slope rei alion ships, 1973. 36 
Table 6.20 Slope soi I loss rei ations for each season 
for maize-maize (no-tillage) and cowpea-
maize (plowed) trealments. 37 
Table 6.21 Effect of soi I and crop management on soi I 
loss. 37 
Table 6.22 Effect of different stages of growth of 
rnai ze on soi I erosion. 38 
Table 7.1 Effect of mulch rate on runoff loss (mm), 
First season, 1974. 43 
Table 7.2 Effect of mulch rate on runoff 10 s s (mm), 
Second season, 1974. 43 
Table 7.3 Mulch rate and runoff, multiple regression 
analysi s. 44 
Table 7.4 Slope· runoff r~lations for di fferent mulch 
rates.(High rainfall) 44 
Table 7.5 Slope- runoff relations for different mulch 
rates. (Low rainfall). 46 
Table 7.6 Mulch tate and soil loss, multiple regres-
sion analysis. 47 
Table 7.7 Slope-soil loss relations for different mulch 
rates. 47 
Table 7.8 Slope-soil loss relations for"different mulch 
rates. 50 
Table 7.9 Mul ching effects on soil I 0 5 sunder diffe rent 
slopes (Mut cll factor) 50 
Table 7.10 Mu I ching effects on runoff under di fferent 
slopes (Mulch Factor). 50 
xii Soi l erosion problems on an alfisoC in Western Nigeria 
Table 8.1 Correlation coefficient and linear regres~ 
sion equations for runoff and soil loss from 
bare fallow with amount of rainfall and 
relating runoff and soil loss from one slope 
to that of others 1(1972). 56 
Table 8.2 Correlation coefficient and linear regres­
sion equations for runoff and soil loss from 
bare fallow plot 5 wi th amount a f rain fa II 
and relating runoff and soil loss from one 57 
slope to thai of others(1973). l-
Table 8.3 Correlation coefficient and linear regres­
sion equations for runoff and soil loss from 
barefallowplots with amount of rainfall and 
relating runoff and soil loss from one slope 
to that of others (1974). 58 
Table 8.4 Correlation coefficients and regression 
equations relating rainfall amount A with 
erosivity indices (1973). 59 
Table B.S Correlation coefficient (r) of run-off at dif­
ferent slopes (%) with various indices(1972) 59 
Table 8.6 Correlation coefficient (r) of run-off at dif­
ferent slopes (%) with various indices(1973) 50 
Table 8.7 Correlation coefficient (r) of run-off at dif­
ferent slopes (1%) with various indices(1974) 50 
Tabl e 8.8 Correl atian coeffi ci ent (r) of soi I loss at 
different slopes (%1) with various erosi-
vityindices(1972). 61 
Table 8.9 Correlation coefficient (r) of soil loss at 
di fferent slopes (1%) with various erosi-
vity indices (1973). 61 
Table B.l0 Correlation coefficient (r) of soil loss at 
di fferent slopes (1%) with various erosivHy 62 
indices (1974). 
Table 8.11 Correlation coefficients of various erosi-
vity indices with runoff and soil loss. 62 
Table 8.12 Weighted mean average correlation coeffi­
cient (1) of various erosivity indices with 
runoff and soi I loss from 10% slop e p 10 t 
with barefallow treatment. 64 
Table 8.13 Computation of Aim and Ebo index for a 
rainstolTTl on 16th June, 1972. E = (foot-ton 
per acre inch) ~ 91& + 331 log,ol (where 
I == inch/hr.) 67 
List of Illustrations (Tables) x iii 
Table 9.1 Effect of contour length on runoff and soil 
loss under maize-cowpea rotation. First 
season, 1972. 73 
Table 9.2 Effect of contour length on runoff and soil 
loss under maize-cowpea rotation. First 
season, 1973. 74 
Tabl e 9.3 Effect of contour I ength on runo ff and soi I 
los s under bare fallow treatrrent. 74 
Table 10.1 Nutrient loss in runoff water (kg/ha) for 
di fferen t slopes and soi I management treat-
ments. (First season 1972). 82 
Table 10.2 Nutrient loss in runoff water {kglha) as 
affected by different slopes and soil man­
agement treatments. (Second season 1972).82 
Table 10.3 Nutrient loss in runoff water (kglha) as 
affected by different slopes and soil man­
agerrent treatments. (Fi rst 5 eason 1973). 83 
Table 10.4 Nutrient loss in runoff water (kg/ha) as 
affected by di fferent slopes and so iI man­
agement treatments. (fiecond season 1973). 83 
Table 10.5 Contour length and nutrient loss (kglha) in 
run-off. First season 1972. 84 
Table 10.6 Contour length and nutrient loss in water 
kg/ha. First season 1973. 84 
Table 10.7 Nutrient loss in run-off water (kg/ha) at 
different mulch rates (tons/ha). First sea-
son, 1974. 91 
Table 10.8 Nutrient loss in run-off water (kg/ha) at 
different mulch rates (tons of straw/ha) 
Second season, 1974. 91 
Table 10.9 Effect of slope length on nutrient loss in 
water run-off under bare fallow. First sea-
son, 1974 92 
Table 10.10 Effect of slope length on nutrient loss in 
water run-off under bare fallow. Second 
season, 1974. 92 
Table 11.1 Nutrient loss in eroded soil (kg/ha) as 
affected by different slope and soil man-
agemen t treatments. First season, 1972. 99 
Table 11.2 Nutrient loss in eroded soil (kg/ha) as 
affected by di fferen t slope and soi 1 man­
agement treatments. Second season, 1972. _99 
XlV Soil erosion problems on an alfisol in Western Nigeria 
Table 11.3 Nutrient loss in eroded soil as affected by 
slope and soil managements. First season, 
1973. 100 
Table 11.4 Nutrient loss in eroded soil as affected by 
slope and soil managements. Second sea-
son, 1973. 100 
Table 11.5 Contour length and nutrient loss in eroded 
soil (kg/ha). First season, 1972. 101 
Table 11.6 Contour length and nutrient loss in eroded 
soil (kg/ha). Second season, 1972. 101 
Table 11.7 Contour I ength and nutrient loss in eroded 
soil (kg/ha). First season, 1973. 101 
Table 11.8 Contour length and nutrient loss in eroded 
50i I (kg/ha). Second season, 1973. 
Table 11.9 Effect of mulch rate (ton/ha) on nutrient 
loss (kg/ha) in eroded soil (First season, 
1974). 102 
Table 11.10 Effect of mulch rate (ton/ha) on nutrient 
loss (kg/halin eroded soil, Second season. 
1974. 102 
Table 11.11 Effect of contour length on nutrient loss 
(kg/ha) in eroded soil. First season. 1974. 104 
Table 11.12 Effect of contour I ength on nutrient loss 
(kg/ha) in eroded soil. Second sea5On.1974 104 
Table 12.1 The erosion ratio as affected by slope and 
soil management treatments. 109 
Table 12.2 Soil moisture equivalent (99-1) of Hie 
eroded sediments as compared to the field 
soil. 110 
Table 12.3 Average enrichment ratio for different nutri-
ents. 111 
Table 12.4 Soil chemical properties. February 1972. 113 
Table 12.5 Effect of soil management and cropping 
sequence on chemical ~haracteri sti cs of 
the soil (0·10 em layer) July 1974. 114 
Table 13.1 Soil moisture retention at different suc­
tion 5 for bare fallow plot at 24 percent 
slope. 121 
Table 13.2 Effect of depth of soil removed on root 
development. 124 
fA n 
129 
Appendix 1a Run - off and soi I loss records for individual 
rainstorms during 1972. 
Appendi x lb Run - off and soi I loss records for individual 135 
rainstorms during 1973. 
Appendix lc Run - off and soi I loss records for individual. 141 
rainstorms during 1974. 
Appendix 2 Texture of the eroded sediments from bare 147 
fallow plots for individual rainstorms. 
Appendi x 3 Appendix erosivity indices. 155 
Appendix 4a Soil moisture records for 1972. 161 
Appendix 4b Soil mol sture records for 1973. 187 
Appendix 4c Soil moi sture records for 1974. 204 
Soil erosion is a major impediment to the development of successful. 
continuously productive farming systems for the humid tropics. The prob­
lem has been understood qualitatively for many years, but attempts to 
control erosion with measures successfully used in subtropi cal and 
temperate areas have often failed. 
On e reason is that the information on whi ch the design of erosion~ 
control systems must be based is not available in the humid tropics. 
Extrapolation of information gathered in other areas of the world is sd~ 
dom satisfactory. The problem is further complicated by the fact that 
erosion-coRtlOl mcasUlcs developed for subtropical and temperate legions 
are based on relatively expensive land-development methods. The returns 
from production of food crops in the humid tropics are often not suffi cient 
to bear the costs. 
One alternative is to leave the agricultural lands of the humid tropics 
under the forest or tree crops. This solution, however, fails to respond to 
the need for more food to meet the demands of rapidly increasing popula~ 
tions. 
In much of southern Asia, the response to the soU-erosion problem 
has been to leave the more erodible upland areas under forests or under 
limi ted cultivation and to develop valleys and estuarine areas for rice 
production, with careful water management. This, again, is a solution, 
but the problems involved in developing land for paddy rice production 
take many years to re~lve. In Asia,as in many other parts of the humid 
tropics, there is an urgent need to develop methods for crop production 
on upland areas better able to control ero sion. 
The real choi ce is between acquiring the knowledge upon whi ch sound 
land,use practices can be based or seeing the desperate need for food 
{Olce people into unsatisfactory exploitati'Ve and degradative use of soils, 
wi th the result that they become unproducti ve and pressure on the land 
increases further. 
xviii Soil et'Qsion problems on an C11fisol in Western Nigeria 
To collect some of the infonnation needed to develop economic meth~ 
ods of arable farming which are also free from erosion hazard of humid 
tropical areas, a detailed study of soil erosion in relation to food crop 
production was started at the International Institute of Tropical Agricul~ 
ture, (IITA) Ibadan, Nigeria, in 1970. This monograph presents details of 
those experiments, including information on th e rela tion between soil~ 
management systems and soil loss. The results show clearly the supe, 
riority of no,tillage mulch-faaming techniques and of intercropping, the 
practices widely used by indigenolls fanners in these areas. It is now 
n eceSSaIY to extend these results to oth er parts of the hum id tropics, to 
determine how widely the Nigerian results can be generalized and what 
modifications may be necessary tor other soil types and climates. 
DENNIS J. GREENLAND 
Director of Research, IITA 
Acknowledgementl 
The author is grateful to Prof. D.]. Greenland for his helpful comments, 
suggestions and for reading the manuscript. My special thanks are due to 
Messrs R.A.Woodis and J.O.Oyekan for editing the report and to Mr. J. 
G. H. Craig for help in constructing the runoff plots. The help received 
from Drs. B. N. Okigbo, T. Little, M. Garber and T. L.Lawson is also 
acknowledged. Thanks also to the staffs of the Analytical Services Labo-­
ratory and the Communi cations and In forma tion section 0 fthe In temational 
Institute of Tropical Agriculture (lIT A). This monograph is dedicated to 
the field staff of soil physics section, who worked hard after every rain 
to collect the information which made this report possible; 
Soil erosion becomes a serious problem in the humid tropics when 
continuous farming replaces shifting cul ti vation and bush fallow. Soil 
erosion includes both physical removal of surface soil and deterioration 
in soil physical properties resulting in low productivity. Failure to appre~ 
date the significance of the soil erosion problem can lead not only to 
large areas of shallow, badly eroded and unproductive soil in the tropics, 
but also to the replacement of forests by savannah. 
The areas of West Africa where potential erosion problems exist are 
shown in Fig. 1.0. Areas wi th annual rainfall higher than 1000 mm. are 
subject to erosion when forests are removed for intensive and large-scale 
mechanized agriculture. 
fZ1 Areas su sooptibie to 
rainfall erosion. 
III Areas susceptible when 
;± vegetation cover is removed 
Fig. 1.0 Relationsnip of rainfall distribution with soil erosion hazard in 
West Africa. 
This report describes in detail the results of a series of fi eld experi~ 
ments conducted at the International Institute of Tropical Agriculture 
(lIT A), Ihadan, Nigeria. These experiments were conducted On al f; "",I", 
and the results may be applicable to similar soil anel r];~ 
elsewhere in the tropics. 
• 2 
Runoff Plot/: Location, De/tqn 
and Con/tructlon 
Westem State of Nigeria lies roughly between longitudes JO and 6 0 
east and latitudes 6° and go north with an average rainfall of 1100 to 
1300 mm. Because of the bimodal pattern of rainfall distribution there are 
t"o growing seasons. The first growing season, from late March to late 
July, ends in a short dry spell that lasts about one month; the shorter 
second season begins in late August and ends in December. 
Run-off plots were. constructed on well drained soi I s belonging to 
Egbeda series (Smyth and Montgomery, 1962). These soils are derived 
from fine-grained biotite gneiss and schist parent materials . They are 
medium-to-light textured near the surface, with sandy-clay to clay sub­
soil and a layer of angular and sub-angular quartz gravel immediately 
below. These soils are classified as Oxic Paleustalf (USDA), Ferric 
Luvisol (FAG) or alfisols. Details of the pedological, physical and chemi­
cal soil characteristics for these and similar soils are described in an­
other report (Moomann, Lal and Juo, 1975). The run-off plots were located 
on natmal slopes along a toposequence (Fig.l.!). There are, therefore, 
local variations in soil texture among and within the slopes. 
wlathe, • .,tton 
500 qt., 
Fig. 1.1 The approximate locations of runoff plots of different slopes 
along a toposequence. 
4 Soil erosion problems on an ulf/sol in Western Nigeria 
Run-off and Soil Los s \1 easurin9 Sy s tem 
Four runoff plots were constructed on natural slopes of arout 1, 5, 10 
and t5%. The exact slopes [or each of the plots are shown in Tabl e 2.1. 
All plots were 25 x 4 m with aIm buffer zone be tween adjacent plOlS. 
There were five plots on each slope, with two additional plots 12.5 m 
and 37.5 m long on the 10 and 15% slopes. 
Table2.t. Slope characteristi cs of each run-off plots 
Slope l%) Nota- Exact Slope 
Plot No. Plot length (mJ Rem arks 
(;on in the Text 9-0 
t 1.80 25 
2 1 1.30 25 
3 1 1 .10 25 
4 1 1.00 25 
5 1 0.88 25 
6 5 4.72 25 
7 5 5.12 25 
8 5 5.48 25 
9 5 5.68 25 
10 5 5.68 25 
11 10 8.76 25 
12 10 9.28 25 
13 10 9.72 25 
14 10 9.88 25 
15 10 10.12 25 Old termite hi ll 
cov eri ng 4 m 2 
area 
16 10 9.33 37.5 Compl ex slope 
17 10 10.00 12.5 
18 15 19.20 12.5 Concave slope 
19 15 13.44 37.5 Compl ex slope 
20 15 14.92 25 
21 15 14.40 25 
22 15 14.16 25 
23 15 14.36 25 
24 15 14.64 25 
Each plot was constructed with an impervious asbestos edging extend­
ing 30 em below and 15 cm above the ground on both sides to prevent run­
off entering from outside. The top edging consisted of 30 em asbestos 
Runoff plots: Locat ion, Design and Conslnlction 5 
sh eeting below th e ground and a IS-cm-hi gh earth embankment lh a t made 
it possibl e to cu lti vate th e soil with a s ma il tractor. The plot edging was 
attach ed to the so il- and wa ter-coll ec tion system at th lower ide . The 
soil- and water- co ll ec tion sys tem was insta ll ed be low till' groun d urrace 
and was a modi fication of th a t des cribed by Wiltsh ire ( 1947 , 194 ) and 
shown in Plate 1. a - g below : 
(a) Collection system with apron and sill installed toward 
th e lower end of the plot. In the bottom righ t hand side 
in the upper portion of the Neutron Probe Access Tube. 
(b) Bare fallow plot with complex runoff coll ect ion system. 
In the center of the plot is a non-recording rain gauge. 
6 Soil erosion problems on an allisol in Western Nigeri a 
(c) Close up of the flume, a 90° V-notch, sill well and 
water I evel recorder. 
(d) Sedimentation and storage tank with two screens and a 
divisor system in the last compartment. 
,R unoff plots: Loca tion, Design and Constmction 7 
(e ) Multi-divisor system and an over-f low tank. 
(f) A complete over-view of the retaining wall , trench and 
coil ection system. 
8 Soil erosion problems on an al/isol in Western Nigeria 
(g) An over-all view of the crops being grown in the runoff 
plots. 
( i) Apron and Sill : Runoff and eroded soil pass over a 4 x 0 .5-m level 
modification sill fixed in the ground by a 15--cm deep extens ion. Runoff 
water is concentrated in the cen ter, from where it passes to an apron and 
flume. Some of the soil carried in th e runoff water can be deposite lo ver 
this level sill. The apron is 0.5 m wide, 1.0 m long and IS cm hi gh. A 
mesh screen of 5 x 5 mm at th e entrance of the apron was in s tall ed to 
prevent stOnes or crop residu e material from entering the flum e. 
( ii) Flume : A 90° V-notch flume was installed within th e apron to ml'a­
sure th e rate of flow. The height of wa te r flowing through th e V-no tch is 
recorded using a still well system and an automatic water level reco rder. 
(iii) Sedimentation Tattll : Runoff from the rate-meas uring flum e passes 
into the sedimentation tank. Sedimentation tank consists of a rectangular 
box 120 cm long, 70 em wide and SO cm deep. Th e s edim entati on tank is 
divided into three equal portions . In the first portion is a silt trap , a tray 
60 cm long, 30 cm wide and 30 cm deep. Also install ed in th e ed im nla­
tion tank are two screens of 5 and 8 mesh to an in ch. Afl er lh e \\a ler is 
filtered through the silt trap and the two screens , it passes inlo th e las t 
compartment consisting of a [lartitioning device. Th e -sedim enlation tank 
was installed on a le vel surface. 
Runoff Partiliorrir19 Devi ce: Twenty- fi ve coppe r tubes 2. 5 em in Lli a­
meter and 10 em long were in s tall ed 40 em a bove th e bo ttom o f the th irLl 
Rwwff plots: Location, Design and 'Construction 9 
compartment of the sedimentation tank. Runoff from the central tube is 
collected into an overflow tank. 
OlJerJlow Tank : The overflow tank consists of an oil drum 58 em in dia­
meter and 90 em deep. A drain pipe installed 5 em above the tank bottom 
facilitates drainage of excess material. 
Drainage System : Sedimentation and o'/erfiow tanks were installed in a 
trench dug aeross the lower end of the plots. The vertical surface toward 
the runoff plots is supported by a retaining wall. The trench base is 
cemented and has a 1 % slope. The drainage is provided through an under­
ground pipe. 
Subsurface Water Collection System : The inter,flow water in the 15% 
slope plots can be collected at a depth of I m. Horizontal drain pipes 
were installed at the lower end of the plot at 100 and ISO-em depth. The 
collection of inter-flow water is facilitated by pipes 2.5 em in diameter 
installed through the retaining wall. 
Neutron Probe Access Tubes : Soil-moisture measurements in each plot 
are made with the help of the neutron moderation technique. Neutron probe 
access tubes were installed about 1 m from the upper and lower ends of 
the plots. 1n tile experiments reported here soil- moisture con tents were 
measured weekly at 30-cm intervals hom the 30, to nO-em depth. One 
field cali bJation was done for each of the four slope plots. Soil hetero­
geneity may introduce error in the calculations of absolute moisture con' 
tent lor various plots within each slope. The Neutron equipment used for 
these measuremen ts was the TorxIer Model 104-A. 
Weather StaLiotJ: A weather station was installed at the highest point 
within the same toposequence. A self-recording rain gauge (Belfort Model 
5-780), an ordinary rain gauge, an American class A pan evaporimeter, 
a pyreliograph (Bel fort), a hygrothennograph and an anemometer were 
installed in this station. 
The plot sizes and the capacity and desil;l of the soiL- and water­
collection system were based on preliminary experiments conducted on 
an adjacent location during 1970. 
10 Soil eros;onproblems on an alfisol in Western Nigeria 
• 
REFERENCES 
1. Moormann, F. R., R. Lal, and A. S. R. 1uo (1975) Soils of JITA. 
IITA Technical Bulletin No.3, 1975. 
2. Smyth, A. J ., and R. F. Montgomery (1%2). Soils and land use 
in Central Western Nigeria. Govt. Printer, lbadan, Nigeria. 
3. Wiltshire, G. R. (1947). Runoff plots and Standard Runoff and 
Soil loss measuring equipment used in Ihe New South 
Wales Soil (,.onservation Service. J. Soi t Conserv. Servo 
N. S. W. 3: 171-178. 
4. Wi]tshirc,G. R. (1948). The measurement s of runoff and Soil 
Loss from Plot experiments. J. Soil Conser\,. Servo 
N.S.W.4:40-44. 
• 3 
Preliminary runoff experiments were conducted during 1970 on 25m x 
3m plots on the four slopes mentioned in the previous section. The soil, 
and water~ collection system was not installed. Runoff was coll ected in 
p]astic,lined trenches at the lower end of the plots . The results. at best , 
are only approximate and of only relative importance. 
The effects of different crops on run a ff losses are shown in Table 3.1. 
Soi 1 losses under different treatments were not measured for all stonn s . 
Soil losses from different treatments relative to natural vegetation for two 
rainstorms are shown in Table 3.2. 
About 60% of the eroded soil consisted of sand and gravels (Tabld.3). 
Table 3.1. Effeet of crop cover and mulching on run~off (eml, September­
December, 1970. Total Rainfall = 29.5 em. 
Slope Maize MfJize-Cowpea Bush 
% Maize (MulChed) Alternate Strips Regrowth 
1 1.9 0.6 2.1 0.5 
5 11.9 2.3 12.1 0.4 
10 12.5 1.7 6.5 0.5 
15 5.2 0.5 7.3 0.6 
Table 3.2. Relative Soil Loss under Different Vegetation and Crop Cover 
(Relative to Natural Vegetation plot of 1% slope) 
Slope Maize Maize Maize-C owpeas Bush 
% (Mulched} A Itemate Strips Regrowth 
329 2 104 1.0 
5 374 24 337 1.5 
10 352 0.5 125 2.0 
15 348 0.8 53 2.0 
12 Soil erosion problems on an alfisol i71 Western Nigeria 
Average nutrient concentrations in the runoff water of two storms are 
shown in Table 3.4. The concentration of inorganic P waS generally low; 
the concentrations of Ca and K, high. The average nutrient losses for all 
slopes and for all crops are given in Table 3.5 . 
. Table 3.3 Particle size distribution of the composite samples of the eroded 
sediments. 
Stope Gravel % Sand Silt ClaV 
96 4nm 2.38-4mm 2-2.38mm % % % 
1 16 11 5 29 29 10 
5 4 4 3 45 28 16 
10 14 9 5 39 23 10 
15 16 8 3 42 25 6 
Table 3.4. Nutrient concentration in the run-off water {ppm} Average of two 
rai n storms f 
Slope Maize Maize (mulch) Maize-Cowpea Bush regrowth 
% P Na Co K P Na ea K P Na Co K P Na ea II 
1 0.1 1.5 21.8 5.2 0.1 1.8 4.3 5.0 0.1 2.5 35.0 16.50.11.3 2.7 1.7 
5 0.2 2.3 14.5 8.4 0.3 1.7 4.5 10.9 0.1 2.0 29.5 10.70.1 1.5 2.6 2.1 
10 0.7 1.7 5.6 7.9 0.3 1.7 1,4 2.1 0.5 2.4 5.8 4.5 0.42,2 1.6 2.8 
15 0.5 1.1 1.8 3.0 2.1 1.4 2.1 4.5 2.2 La 2.7 3.8 0.6 1.6 1.4 2.3 
Table 3.5. Total nutrient loss in run·off water (kgl1la/season). 
Crop P04'P Ca K Na 
Maize 0.3 7.3 5.6 1.4 
Maize (mulched) 0.2 0.4 0.8 0.2 
Maize-Cowpea 
(Alternate strip) 0.5 12.4 5.5 1.3 
Bush Regrowth 0.1 0.1 0.1 0.1 
During one growing season 0.1 to 12 kg/ha of Ca and 0.1 to 6 kg/ha 
of K were lost. The maximum loss of inorganic P was 0.5 kg/ha. 
The relative nutrient concentrations in eroded soil (Table 3.6) indi­
cate that most or the nutrient loss in runoff water is associated with 
eroded sediments. The concentrations of P, Ca and K in the fine fraction 
Results of the Preliminary Experiments 13 
Table 3.6. Nutrieot contents of the composi te sample frorr eroded sediments (ppm) 
Slope Coarse / Maize Ma ize (mulch) Maize·Cowpea Bush Regrowth 
% fint! p Ca K P Ca K P Ca K P Ca K 
C 4.4 390 25 4.0 450 60 4.6 563 53 1.4 410 53 
F 18.1 9B5 58 9.3 955 105 11.1 950 62 3.9 475 105 
5 C 3.9 275 58 2. 0 213 38 1.6 475 94 1,4 325 51 
F lB.l 788 98 2.3 775 101 28.1 1113 128 5.5 725 70 
10 C 4.2 320 18 4.9 180 22 2.9 170 26 9.2 125 16 
F 28.1 995 102 13.5 775 132 9.2 745 90 8.2 790 90 
15 C 33.4 248 58 4.6 204 35 9.8 234 51 4.7 138 21 
F 65.3 1515 154 10.9 1060 168 53.0 690 103 14.7 1135 82 
C = Corse fraction 
F = Fine fraction 
(<2mm) were double those in the coarse fraction. The K content of the 
eroded soil from the mulched~maize plots was generally higher than that 
of the soil eroded from the unmulched~maize plots. 
Conclusions: - From these preliminary results, the following conclusions 
were drawn: 
(i) The runoff plots should at least be 4m wide with a buffer zone of 
1 m between adjacent plots. 
(ii) Runoff and erosion losses from mulched plots were significantly 
lower than those from unmulched plots and were equal to those 
from plots with bush regrowlh. 
(iii) Nutrient losses in runoff water were not high,though relative nutrient 
concentrations might present a potential pollution hazard. 
(iv) Most of the nutrient losses occurred in eroded soil, particularly in 
the finel fraction of the eroded sediments. 
Based on these conclusions, permanent runoff plots were designed and 
constructed during 19'71. Plot design, con struction and layout are shown 
in Chapter 3. It was also evident that straw mulching of the soil surface 
might be an erosion preven ti ve practice and some techniques of managing 
residue to produce mulch il1~sitll may prove important cultural practices 
for fanning systems in the tropics. The treatments designed for the pe.rrna~ 
nent runoff plots were based on these preliminary findings. 
• 
Treabnentl 
Experiments on the permanent runoff plots were conducted from 1972 
to 1974. Soil~ and crop~managernent treatments for the 1972 and 1973 
expeliments are shown in Table 4.1. 
First-season crops were planted on 10 April; second season crops, 
on 10 August. Crops were planted in rows running up and down the slope. 
Maize was planted at 75 cm between and 25 cm within the rows and 
recei ved 120 kg/ha of N (1/3 at planting and 2/ 3 four weeks after) and 
60 kg/ha each of P and K. The mulched plots received 6 ton/ha of rice 
straw, applied on the surface after planting. No~tillage plots were treated 
with paraquat (l~ 1 dimethyl 1~4, +bypridinium ion) at the rate of 2.5 t!ha 
applied one week before planting. All other plots were disk~plowed and 
harrowed. 
Because the soil had been disturbed during plot construction and there 
was no crop residue on the soil surface, the no~tillage plots were not 
effectively treated during the first season of 1972. The runoff and erosion 
results reported, therefore, have to be evaluated as results for disturbed, 
unmulched soil~surfaces. 
Treatment allocations for 1972 and 1973 were randomized as shown in 
Table 4.2. 
Table 4.1. Soi I and crop management treatments for 1972-73. 
Treatment No. First season Second season 
Bare fallow Bare fallow 
2 Maize (mulch) Maize (mulch) 
3 Maize (con\lentional plowing) Maize (conv. plowing) 
~. Maize (no tillage) Cowpeas ( no tillage) 
5 Cowpeas (conventional plowing) Maize (conv. plowing) 
16 Soil erosion problems on an alfisol in Western Nigeria 
Table 4.2. Treatment allocation to run-off plots for 1972-73. 
Run-off plots no, Treatment No Treatment description 
2 maize-maize (mulch) 
2 3 maize-maize (conventional plowing) 
3 1 bare fallow (conventional plowing) 
4 4 ma;ze-cowpeas (no tillage, herbicide 
weed contro I) 
5 5 cowpeas-maize (convention al plowing) 
6 4 ma;ze-cDwpeas (no tillage, herbi c ide 
weed control) 
7 2 maize-maize (mulch) 
8 3 maize-maize (conventional plowjng) 
9 4 cowpeas-maize (conventional plowing) 
10 bare tal low (conventional plowing) 
11 1 bare fallow (conventional plowing ) 
12 2 mai ze-mai ze (mulch) 
13 4 maize-cowpeas (no tillage, her~icide 
weed control) 
14 5 cowpeas-maize ( conventional plowi ng ) 
15 3 maize-maize (conventional plowing ) 
16 6 maize-cowpeas (convent ional rlowing j 
17 6 ma;ze-cowpeas (conventional plowing) 
18 E maize-cowpeas (conventional plowing ) 
19 6 maize-cowpeas (conventional plow i ng) 
20 4 maize-cowpeas (no tillage, herbicide 
weed control ) 
21 2 maize~maize (mulch) 
22 4 cowpeas-maize (conventional plowing ) 
23 3 maise-maise (conventional plowing) 
24 bare fallow (conventional plowing) 
No crops were grown during 1974 and the plots received different rates 
of surface mulching. Runoff and soil losses from plots with mulch rates 
of 0, 2, 4 and 6 tons/ha were compared with those from the no~tillage 
plots. All 120 kg/ha of N and 60 kg/ha of each of P &1 K_ Th ese experi­
ments were rallied out for two consecuti ve seasons. Treatmen t allocations 
for L974 are shown in Table 4.3. 
Treatments 17 
Table 4.3. Treatment allocation for 1974. 
Run-off p lot No. Mulch treatment (tonslha) 
1 6 
2 2 
3 o 
4 No-ti Ilage 
5 4 
6 No-ti Ilage 
7 6 
8 2 
9 4 
10 o 
11 o 
12 6 
13 No-tillage 
14 4 
15 2 
16 o 
17 o 
18 o 
19 o 
20 No-tillage 
21 6 
22 4 
23 2 
24 o 
Soil and runoff water from each of the plots were collected after every 
storm. Eroded sediments from each plot were dried and processed sepa­
rately for physical and chemical analyses. A representative sample of 
the runoff water from each stonn was collected to detennine sediment 
densi ty and nutrient concen tration. 
• 5 
In addition to rainfall amount, rainfall intensity, distribution of storm 
intensity, kin etic energy, momentum and drop size are important para~ 
meters affecting soil erosion . 
Intensity : The frequency distrilxrtion of rainfall intensity for 1972 to 1974 
is shown in Figure 5.1. The 7.5~minute maximum intensities of 61 % of the 
rainstonns in 1972 and 57% of those during 1973 were between 25 and 75 
mm hr~1 Seventy~six percent of the storms during 1912 and 66 % of those 
during 1973 had maximum intensities greater than 25 mm hr~l. Intensities 
exceeding 75 mm hr ~1 were recorded for 15% of the rainstorms during 1972 
and 10% of those during 1973. 1ntensities greater than 100 mm hr~l were 
recorded for 7% of the storms during 1972 and 3% of those during 1973. 
The 7.5~minute maximum intensities of 48.3% of the rainstorms during 
19']4 were greater than SOmm hr~l Twenty~one percent of the stonns had 
maximum intensities greater than 75mm hr~1 About 14% of the rainstorms­
had intensiti es greater than 100mm hr-l~ half of those with intensities 
of 130mm hr~1 
Rainstorm int ensity rarely exceeds 75mm hr-1 in temperate climates. 
Tropical rainstorms , however, are more intens e . As the data in Figure 5.1 
indicat e, 15, 10 and 30% of storms during 1972, 1973 and 1974 respec­
ti~'ely , had intensities greater than 7Smm 1.u~l.StoIIn8 with rainfall inten~ 
sHies greater than 130 mm hr~l were also observed. 
Inten silY Dis triburiml : Some storms have their highest intensities in the 
begiIming and lowest intcnsities during later stages. For example, an 
intensity of 213mm hr~l was recorded during the first five minutes of a 
storm on 26 April ]973. Most storms fit this pattern (Fig. 5.2). 
Othe r storms begin wi th medium intensity and reach their peaks in the 
middl e (rig. 5.3). There are also composite storms with peak intensities 
within two to thrce hours of one another (Fig. 5.4). Each intensity distri­
bution presents a different soil~erosion hazard. Interpreting the erosion 
data {rom composite storms is more difficult. 
20 Soil erosion problems on an alfisol in Western Nigeria 
1972 
2 4 
2 0 
6 
12 
a 
4 
0 r f r 
197 :3 
2 S 
2 4-
iP 0-
is 
-10 16  
o 
2 
8 
4 
0 J J I 
1974 
32 
28 
24 
20 
16 
12 
B 
4 
o I 
25 50 75 100 125 \ 150 175 
int.noB y (mll".lhr) 
Fig. 5.1 Rainfall intensity distribution of storms from 1972 to 1974. 
Rainfall Erosivity: Erosi vity is the potenti al abi1i ty of rain to cause 
erosion .. Energy to dislodge and detach &)il particles in the erosion pro~ 
cess is provided by the kinetic energy of the rain. Wischmeier (1955) and 
Wiscbmeier et at (1958) found that the E130 index was most significantly 
correlated with the erosion. This index is a product of the kinetic energy 
of the storm and the 3~minule maximum intensity. The 30'minutc intensity 
is the greatest average intensity recorded during any 3()-minute period. 
Rainfall characteristics 21 
250 
30 
20 
10 
O L---~0~--~IO----~----~20~--~25~---3~O----~3~5====~4O~----­
lime (minI 
Fig. 5.2 Rainfall intensity distribution during a sm"" with the peak in­
tensity occurring in its beginning. 
Hudson and Jackson (1959) found from their studies in Rhodesia that 
although the El30 index provided an accurate measure of erosi vity of 
rainstorms in temperate America it was less effective in tropical Africa. 
He developed an alternate procedure based on the concept that there is a 
threshold intensity value at which rainfall becomes erosive (2Smm per 
hour). Thi s index is call cd KE >1 . 
22 Soil erosion problems on Dn allisol in Westem Nigeria 
.60 
170 
160 
1!l0 
140 
130 
)20 
110 
10 
~ 
E 90 
e 
80 
A 
....   70 
c 
60 
$0 
40 
30 
20 
10 
0 
10 I 20 2S 30 3!5 4Q 4~ !l0 !IS 60 66 10 75 eo es 90 35 100 
II. .. (min, 
Fig. 5.3 A stOIll1 with a low initial intensity and a second peak immedi­
ately following a high peak. 
•• e CO "POSITt $10""$ 
7(-
' 0: 
. ~ C 
l:!Ie 
.20 
0,0 
000 
~ ... 
~(: 
,. 
- \ 
-. 
~ ' . 
.. e 
1 C 
20 
.0 l 
11l1li. (III .. .) 
Fig. 5.4 A composite stonn with two separate intensity peaks spaced 
widely apart. 
Rainfall characteristics 23 
Intensity records at UTA, Ibadan , indicate that most stonns have high 
shorHenn intensities. Erosivity indices were calculated to incorporate 
maximum average intensities for 7.5, 15, 22.5, 30, 37.5 and 45 minutes. 
Different erosivity indices are compare'd in Chapter 7. 
REFERENCES 
1. Hudson, N. W. and D. C. Jackson (1959). Results achieved in the 
measurement of erosion and runoff in Southern Rhodesia. Third 
Inter,African Soils Conference, Dalaba. Proc. 2:575-584. 
2. Wischmeler, W. H. (1955). Punch cards record runoff ana soil loss 
data. Agric. Engineering 36:664-666. 
3. Wischmeier, W. H., D. D. Smith and R. E. Uhland (1958). Evaluation of 
Factors in the SoiHoss Equation. Agric. Engineering 30:458-
462, 474. 
4. Wischmeier, W. H. and D. D. Smith (1965). Rainfall Erosion Losses 
from Cropland East of Rocky Mountains. Agricultural Hand­
book 282, USDA, Washington, D. C. 
• 6 
ateb r'~ IOIlel f()f 
l lj()':,)~E?l ,)('\d loll 
jf,,P ,,,'i.j~;i ;t~.,a (t!' c' \~,.lf, ,~",!,f't'';',':'', ','§'''  
Exponential I elation ships between slop e and erosion losses have been 
reported by various workers (Zingg, 1940; Wischmeier et aI, 1958), Hudson 
and Jackson (1959) reported from their work in Rhodesia that for tropical 
soils the slope coefficient approaches a value of 2. Wischmeier (1966) 
reported the relation between slope and runoff loss to be logarithmic,Other 
studies have shown no relation between slope and runoff (Borst and 
Woodburn, 1942). 
Use of crop residue as a mulch to reduce runoff and erosion losses has 
extensively been reported (Mannering and \1eyer , 1961 and 196}).NO'tiIiage 
or minimum tillage has also been used effectively to minimize runoff and 
erosion losses (Mannering and Burwell , 1962; Moldenhauer et aI, 1967 ; 
Harrold, 1912). Some studies in West Africa have indicated greater runoff 
and erosion losses under minimum tillage (Chaneau, 1966). 
Minimum tillage results should be interpreted with reference to initial 
soH conditions, e.g. compaction, degree of erosion, and amount of crop 
residue because initial soil conditions under minimum tillage can sil!Jlifi' 
cantly influence soil and water conservation' and crop performance. 
(i) Slope,Runoff Relation : The effects o{ slope and soil management on 
runoff losses for four seasons are shown in Tables 6.1 , 6.2, 6.3 and 6.4. 
There are no significant differences in the runoff losses from bare fallow 
plots on slopes ranging from 1 to 15%. This may mean that runoff losses 
from bare soil are primarily governed by soil physical properties, e.g. 
infiltration rate and surface'sealing characteristics. Runoff losses under 
different crop rotations were of the order of maize,maize (mulch) < maize' 
cowpeas (no,tillage) < cowpeas,maize < maize,maize < bare fallow. This 
sequence does not apply to no,tillage treatments during the first season 
of 1972 because of the lack of crop residue as a surface mulch . . 
Mathematical relationships between runoff and slope based on the 
analysis of individual storms are shown in Tables 6.5, 6.6 , 6.7 and 6.B. 
These results are the combined analyses of first' and second-season 
stonns. Storms with less than 25 nun of rainfall (lowfall) and those with 
more than 25 mm of rainfall (high rainfall) were analyzed separately. The 
correlation coefficients between runoff and slope are generally low,except 
for mulched treatments. 
26 Soil erosion problems on an alfisol in Wutem Nigeria 
Table 6.1. Effect of slope and soil management on run-off loss (mm ).First season 1972 
Total Rainfall-
Soil and crop management treatments 
Slope Bare fallow Maize-maize Maize-maize Maize-cowpeas Cowpeas-maize Mean 
% (mulch J (no-tillage! 
225.6 0.4 69.1 22.4 12.7 66.0 
5 261.6 14.9 170.0 118.2 89.5 130. 8 
10 259.1 15.8 91.9 123.4 30.7 104.2 
15 214.1 13.5 83.2 118.3 32.7 92.4 
Mean 240.1 11.2 103.6 95.6 41.4 
Table 6,2. Effect of slope and soil management on run-off loss (mer). Second season 1972 
Rainfall -
Soil and crop management rteatments 
Slope Bare fallow Maize-maize Maize-maize Maize-cowpeas Cowpeas-malZe Mean 
% (mulch' (no-tillage) 
22.7 0.0 4.5 2.2 5.1 6 .9 
5 39.0 1.9 15.2 4 .0 27.7 17.6 
10 27.6 4.2 9.6 5.2 6.9 10.7 
15 25.5 3.2 9.4 5.3 17 .6 12,2 
Mean 28.7 2.3 9.7 4.2 14.3 
Table 6.3. Effect of slope and soil management on run-off loss (mlf' )' First season 1973 
Rainfall-
So;1 and crop management treatments 
Slope Bare fallo w Maize-maize Maize-maize Maize-cowpeas Cowpeas·maize Mean 
% (mulch) (no-ciffage! 
1 315.7 0.0 55.1 11.4 19.8 80.4 
5 347.3 6.9 158.7 11.8 81.2 121.2 
10 311.0 20.3 52.4 20.3 51.4 91.1 
15 316.5 16.8 89.9 21.0 46.1 116.3 
Mean 322.6 11.0 89.0 16.1 49.6 
Table 6.4. Effect of slope and soil management on run-off loss (mm 1. Second season 1973 
Rainfall -
Soil and crop management treatments 
Slope Bare falJaw Maize-maize Maize-maize Maize-cowpeas Cowpeas-maize Mean 
% (mulch) (no-tillage J 
191.7 0.0 9.1 6.0 22.2 45.8 
5 195.8 4.0 65.D 6.5 64.5 67.2 
10 193. , 9.0 36.0 10.2 30.5 55.8 
Hi 185.4 7.5 71.4 10.7 105.4 76.1 
Mean 191.5 5.1 45.4 8.4 55.7 
Soil and water losses for dif fe rent s lot)es and soil management 
practices 27 
Table 6.5. Run-off slope relation 1972. (a) High Rainfall 
Treatment R2 Equation Average 
Runoff % 
Bare fallow ns ns 42.S 
Mulch 0.11 y= ·0.46 + 0.33 5 2.1 
Maize·maize 0.19 y= · 8.77 + 16.93 S - 2.33 52 + 0.09 S3 16.7 
Cowpea·maize 0.26 y= ·6.32 + 11.S3 s· 1.79 S2+ 0.07 53 7.9 
No-tillage ns ns 14.2 
(bl Low Ra i nfall 
Treatment R2 Equation Average 
Runoff % 
Bare fallow ns ns 14.8 
Mulch 0.40 y= - 0.79 + 0.58 S - 0.03 S2 1.5 
Maize-maize 0.29 y= - 2.97 + 5:88 S - 0.83 S2+ 0.03 53 5.1 
Cowpea·ma i z e 0.24 V:::. -1.39 + 3.545 - 0.52 S2 ... 0.()2 S3 3.8 
No·till age 0.19 y= -1 .35 + 3.30 5· 0.40 S2 + 0.01 S2 5.1 
Table 6.6. Run-off slope relations 1973. (a) High Rainfall 
Treatment R2 Equation Average 
Runoff % 
Bare fallow ns ns 50.7 
Mulch 0.69 V= 0·12 - 0.23 S + 0.10 S2. 0.005 S3 1.3 
Maize·maize 0.29 y= ·10.77 + 15.57 S· 2.27 s2t- 0.09 53 13.6 
Cowp ea-ma i z e 0.15 y= -2.43 + 8.46 S . 1.33 S2t 0.06 S3 10.7 
No·tillage 0.40 V= , .76 ·0.40 5 + 0.09 S2 - 0.004 S3 2.0 
(bl LowRainfali 
Treatment R2 Equation Average 
Runoff % 
Bare fallow ns ns 29.9 
Mulch 0.45 V= -0.95 + 0.56 5 - 0.024 52 1.3 
Maiz e-maize 0.17 ¥= -7.64 + 11.86 5 - 1.77 s2 + 0.07 S3 8.6 
Cowpeas-maize 0.10 y= -3.15 + 6.89 5 . 1.04 52 + 0.04 S3 6.3 
No·tillage 0.13 Y=1.48+0.10S 2.3 
28 Soil erosion problems on an aifisol in Western Nigrna 
Combined analysis as shown in Tables 6.7 and 6.8 may be misleading 
because the crops grown during the first and second season s were <.Ii f­
ferent {or di fferent tillage treatments. During the fi cst season, maize was 
grown on the no-tillage plots and cowpeas grown on the plowed plo lS. 
Table 6.7. Runoff - slope relations 1972. (8) High Rainfall 
Treatment r Equation 
Bare fallow - 0.01 y~ 32: 4 S -0.01 
Mulch 0.79 yo=. 0.0016 S2_99 
Maize-maize 0.09 y= 7.87 SO.12 
Cowpea-maize 0.42 y= 1.95 S0.46 
No-ti Ilage 0.47 y= 0.39 S 0.58 
(bl Low Rainfall 
Treatment [quat/Of) 
Bare fallow - 0.01 y= 8.75 S-O.Ol 
Mulch 0.7B y= 0.008 S2.38 
Maize-maize 0.14 y= 3.2 50. 13 
Cowpea-maiz e 0.60 ¥= 1.18 SO.51 
No-till age 0.55 y= 1.40 S°.56 
Table 6.8. Runoff - sloppe relatiohS 1973. (a) High Rainfall 
Treatment r Equation 
Bare fallow -0.03 y= 46.40 S·0.02 
Mulch 0.92 y= 0.0008 53.35 
Mai z e-ma i z e 0.39 ¥= 4.86 SO.38 
Cowpea-ma i 2 e 0.50 y= 1.62 SO.66 
No-tillage 0.53 V::: 1,23 SO.24 
(a) Low Rainfa II 
Treatment r Equation 
Bare fallow 0.08 v::: 23.1 (\ 5-0·14 
Mulch 0.B4 y= 0.005 SO.26 
Maize-maize 0.15 ¥= 2.66 S C. 26 
Cowpea-maize 0.35 y= 1. 19 SO. 53 
No-tillage 0.18 y= 1.15 SO.20 
Soil and uater losses for different slopes and soil management 
practices 29 
During the second season the crops and treatments were reversed. The 
exponential function analysis was therefore run separately for each of the 
four seasons (Table 6.9). 
Cumulative runoff factors for di fferent crop rotations, averaged over 
the four growing seasons, are shown in Table 6.10. Those factors are 
computed as ratio of runoff or soil loss from a given treatment to that from 
bare fallow plots at a given stage of crop growth. Mulch au.d no-tillage an: 
most effective in preventing runoff. The coefficients for different stages 
of crop growth are shown in Table 6.11. The four stages described in this 
tabl e are as follows: Stage 1 - Plowing, seeding and three weeks after; 
Stage 2 - Crop establishment, from 3 Lo 6 weeks; Stage 3 - Establishment 
to maturi ty, 6 weeks to harvest ; Stage 4 - Harvest un ti I next plowing. 
Table 6.9. Slope run-off relati ons for each season for mai ze-cowpea (no-
tiilage) and cowpea-maize (plowed) treatments 
Treatment Year Season Rainfall R Equation 
Cowpea-maize 1972 High 0.46 Y=2.11S0.41 
(plowed) 
I Low 0.57 ¥= 1.87 S 0.17 
II High 0.40 ¥= 1.62 S0.58 
II Low 0.81 ¥= 1.18 SO.52 
1973 High 0.46 ¥= 1.23 5°·53 
I Low 0.43 y= 1.27 50.54 
II High O.~6 y= 1.925°.74 
II Low 0.27 y= 0.75 SO.51 
Maize-maize 1972 High 0.66 ¥= 1.15 50.68 
(no-ti Ilage) 
Low 0.56 y= 1.50 5°·62 
II High 0.78 ¥= r..98 SO .36 
II Low 0.75 ¥= 1.50 5°·33 
1973 High 0.48 ¥= 1.21 50.21 
Low 0.26 y= 0.7450,21 
II High 0.56 ¥= 1.24 SO.25 
II Low 0.13 ¥= 0.08 50.21 
30 Soil erosion probe ems 011 an alfisol in Western Nigeri a 
(ii) Slope-Soil Loss Reiatiolts : -Slope-soil loss relationships for differ­
ent soil management and crop rotations are shown in Tables 6.12 to 6.15. 
The potential erodibility of a given slope and soil and crop management 
treatment is indicated b)-' the erosion loss under bare fallow. The data for 
the four seasons investigated indicate three important factols that affe ct 
erosion losses: (i) slope, (ii) season and (iii) wil management. Erosion 
losses increased wi th increase in slope. By the second season of 1973, 
the bare-fallow plots on the 10 and 15% slopes had been eroded exces­
sively and a decrease in erosion was recorded because gravel exposed on 
the soil surface acted as a mulch (Figs. 6.1 and 6.2). 
Rainstorms during the first growing season at Ibadan are more erosive 
than those during second season. As a result , the erosion losses are 
lower during the second season. Mulching and no-tillage soil management 
practi ces were most effccti ve in preventing soil erosion, regardless 0 f 
slope. The erosion losses were in the order of maize-maize (mulch) < 
maize-cowpeas (no-tillage) < cowpeas-maize < maize-maize < bare fallow. 
No-tillage treatment during first season 19n was not effective because 
of the lack of crop residue on the soi 1 surface. 
Table 6.10. Crop and soi I management factor 
Rotation First season Second season 
Bare fallow 1.00 1.00 
Maize-maize (mulch) 0.04 0.05 
Ma i ze·ma i ze 0.35 0.29 
Maize-cowpea (no-tillage, 0.05*' 0.10 
Cowpea-rna i ze 0.16 0.40 
* Exluding the first season 1972 date in which case was no crop residue 
and the soil was disturbed. 
Table 6.11. Crop and soil management factor for different stages of ~owth 
(based on 1973 records) 
Rotation 1 2 3 4 
Bare fallow 1.00 1.00 1.00 1.00 
Maize-maize (mulch) 0.048 0.025 0.019 0.039 
Maize-maize 0.70 0.27 0.29 0.114 
Maize-maize 
(no-tillage) 0.075 0.037 0.035 0.051 
Cowpea-ma i ze 0.74 0.'17 0.036 0.068 
Soil and water losses for different slopes and soil management 31 
practices 
Table 6. 12. Effect of s lope and soil management on soil loss itons,1-ta \. First season 1972 
Tota l Rainfall-
Soil and crop management treatments 
Slope Bare falloVl Maize-maize Maize-maize Maize-Cowpeas Cowpeas-maize Mean 
% (mulch I (no-li/lagel 
4.0 0.0 1.0 0.4 0.2 1-1 
5 32.1 0.1 2.7 1.5 1.2 7.5 
10 45.5 0.1 5.8 5.1 2.1 11. 7 
15 101.0 0. 1 13.1 7 .8 1.8 24.8 
Wean 45.7 0.1 5.7 3.7 , .3 
Table 6.13. Effect of slope and soil management on soil loss (tons/hal Second season 
1972. Total Rainfall -
Slope and ClOP Managemefll Treat/rents 
Slope Bare fallow Maize-maize Mai,e-wize Maize-cowpeas Co wpeas'I1'"ize Mean 
% (mutch) (/lo-tillage i 
1 , .0 0.0 0.1 0.0 0.3 0.3 
5 11.1 0.0 0.4 0.0 1.1 2.5 
lD 13,4 0_0 0.6 0.0 0.9 3.0 
15 15.1 0.' 1.3 1.0 4.4 4.4 
Mean 10.2 0.0 0.6 0.2 1.7 
Table 6.14. Effect of slope and soi l management on soil loss Itons/hal. Fi rst season 1973 
Total Rain!,,!! -
So i l and crop management trearments 
Slope Bare fallow Maize-maize Maize-maize Maize-Cowpeas Cowpeas-maJze Mean 
% (mulch I (no-ri /lage ) 
1 7.5 0_0 1.2 0.0 0.6 1.9 
5 80.4 0.0 8.2 0. 2 5.6 l8.9 
10 152.9 0.1 4.4 0.1 3.3 32.2 
15 155.3 0.0 23.6 0.1 7.6 37_3 
Mean 99.0 0.0 9.4 D. l 4.3 
Table 6.15. Effect of slope and soil management on soil loss {:onsAlal Secolld season 
1973. Total Rainfall -
Sod and Crop Managem~nt rreatments 
Stope Bare fallow Maize-maize Maize-maize Ma; ze-COLVpeas Cowpeas-maize Mean 
% (mulch) (no-ti llage! 
1 3.7 0.0 0.4 0.0 0.3 0.9 
5 75.8 G.G 2.S 0.0 4.0 16.5 
10 79.7 0. 1 2.8 0.1 3.0 17.1 
15 73.9 0.0 17.1 0.0 35.4 25.3 
Mean 58.3 0.0 5.8 0.0 1<l.7 
32 Soil rnJsion problmls on an alfisol iJl Western Nig~ria 
1000 
I 3-----0 ba" ''-OW 
2 ---------- ...l zo-,..lallMilch) 
3A----6 ...t z'-mabe 
4'-"'- _I,.-....., .. Ioo-t',-' 
&.............. cowpl'-"'.lz, 
100 
D 
10 
4 
/ 
/ 
/ 
/ 
/ 
,I 
/ 
/ 
/ 
, 0 / 
/ 
/ 
/ 
/ 
/ 
x ,I 
':; I 
c / ,­
.; / 
/ 
/ 
/ 
"··   / 
/ 
"·0  / 
·10 / /' 
,I / 
/ / 
/ / ,­ / 
/ /" 
/ 
/ /" 
/ /" " 
/ 
/ / / 
/ 
J " 
" " I " 
I, , " 
/ " 
r 
·0 / 1 
/ J 
/ I 
/" I 
//" " J / 
J 
J 
J 
I 
I 
f 
I 
~O'l'~-----------------'IQO------------__________ ~~ ________ ___ 
Fig, 6.1 Influence of soil management crop rotations and slope on soil 
erosion in 1972. Note that Y·axis is a log scale. 
Soil and water losses for different slopes and soil management 
practices 33 
t97~ 
1000 
I __ bare fallow 
2 -......-.-. mollB-n'l ahd. r.uLt~- .f 
:5 A.------lI. malu-mnill 
4 0------0 ",oU:'-COWp~.I\t ... riDo .. e) 
/ :5 -------. COIIFII'J-moizA 
/ 
,/  
I 
100 r 
/1 " 
/ 
10 
/,/' ( "4 
•  
t{) // 1/ 
I I I 
/ / I 
I / /1 
~ / I / 
I / / 
c 
!.!  1/1 I 
I / c I 
/ I / 
0 / / 
I I 
/ I o 
"0 
~ / ! 
·10 I / 
/1 / 
/ / I 
I I 
I 
I 
I I 
/ I 
I 
/ 
/ 
I 
' / 
I 
OJ / 
I 
I 
/ 
I 
I 
/ 
I 
I 
/ 
/ 
I 
/ 
.~IL'------~--------~'~O----------------------ro------------
. 10p. % 
Fig.6.2 Influence of soil management crop rotations and slope on soil 
erosion in 1973. Note that V-axis is a log scale. 
34 Soil t1'osion problems on an a/fisol in Western Nigeria 
Slope-soil loss relationships, similar to those of runoff-slope re­
lationships, were computed. Multiple regression analyses of soil loss "'ith 
slope for ruth high and low rainfall are shown in Tables 6.L6 and 6.17 
for 19n and 1973, respectively, Soil loss in the relation is expressed in 
units of kg/ha/mm of rain. The correlation coefficients between soil loss 
and slope were high for bare fallow and maize-maize treatments only. 
Analyses of soil loss slope relations with exponential functions are 
indi cated in Tables 6. 18 and 6.19. Thi s type of analvsi s fi Is the data from 
the bare-fallow and maize-maize treatments bettcr than the data from other 
crop rotations and residu e management treatments. The correlation co­
efficients were always generally high in rainstorms exceeding 25 mm. 
The slope exponents for the high rainfall bare-fallow treatments ranged 
between 1.1 and 1.2. Mulch and no-tillage treatments had the lowest slope 
exponents as well as coefficients. The exponential function of slope-soil 
loss did not apply to the mulch and no-tillage treatmenls and the correla­
tion coeffi cien ts were the lowe st for these managemcn L pracli ces. 
Table 6.16. Multiple regression of soil loss with slope, 1972. 
(a) Hig, Rai nfall (25 mm) 
Treatment R2 Equation Average Y 
kglhafrml 
Bare 0.41 y= -2.1+11.2 S 82.3 
Mulch ns ns 0.04 
Maize-maize 0.29 y= -3.8+1.7 S 9.7 
No-tillage 0.34 y= ·2.4+1.1 S 5.8 
Cov.pea-mai ze 11 5 ns 5.7 
(b\ Low Rai nfall ( 25 mm) 
Treatment R2 Equation Average Y 
kg/fJa,1nm 
Bare 0.13 y= -0.6"1.6 S 57.0 
Mulch 0.03 y= -O.OO-t{).03 S 0.16 
Maize-maize O.(!i 2 
y= -1.3+2.3 S - fl.4 S 
+ 0.02 S3 2.5 
No-tillage 0.00 y= -O.2-t{).5 S 3.3 
Co..-.pea-maize 0.04 ¥= -O.09-t{).3 S 2.3 
Soil and '/Later losses for different slopes and soil management 
practices 35 
Table 6.17. Soil Loss-Slope Relationships, 1973 
(a) High Rainfall 
Treatment R2 Equation Average Y 
kglhalmm 
Bare fa l low 0.42 y= ·33.5+40.2 S - 1.65 S 2 136.9 
Mulch ns ns 0.47 
Maize-maize 0.42 y= -12.0+12.9 S • 2.2 S2+ 15.1 
0.1 53 
No-tillage ns ns 0.12 
Cowpea-rna i z e 0.24 y= .-6.6 - 4.6 S + 0.5 5 16.7 
(b) Low Rai nfall 
Treatment R2 Equation Average Y 
kg/halmm 
Bare fallow 0.31 y= ·37.9+49.8 S • 2.6 S 127.8 
Mulch ns ns 0.24 
Maize-maize O.Hi Y=-·5.1 - 2.1 S + 0.2 S 9.2 
No-ti Ilage 0.05 y= -0.009+0.09 S . 0.006 S 0.17 
Cowpea-ma i ze 0.04 V= -1.2+0.9 S 1.B 
Table 6.18, Soil Loss-Slope Relationships. 1972 
(a I Hi gh Rainfall 
Treatment r Equation 
Bare fallow 0.75 y= 6.0 S 1.11 
Mulch 0.28 V= 0.016 SO.50 
Cowpea·mai ze 0.37 y= 0.32 S 1.02 
Cowpea-maize 0.21 y= 0.11 50.52 
No-ti II age 0.46 y= 0.12 51•14 
36 Soil ervsion problems on an alfisol in Western Nigeria 
(b O) Low Rainfall 
Treatment r Equation 
Bare fallow 0.30 y= 1.6 SO.82 
Mulch 0.14 y= 0.08 SO.15 
Maize-maize 0.76 y= 0.48 5°·20 
Cowpea-maize 0.20 y= 0.18 SO.34 
No-tillage 0.33 y= 0.18 5°·63 
Table 6.19, Soil Loss Slope Relationships, 1973 
(a) High Rain fall 
Treatment r Equation 
8are fallow 0.86 y= 9.57 51 .21 
Mulch 0.47 y= 0.02 SO.66 
Maize-maize D.52 y= 0.59 S 1 .13 
Cowpea-covvpea 0.45 y= 0.13 Sl,19 
No-tillage 0.17 y= 0.043 SO.16 
(bl Low Rainfal! 
Treatment r Equation 
Bare fallow 0.48 y= 4.26 S 1.26 
lAulch 0.14 y= 0.08 5°·15 
Maize-maize 0.29 y= 0.3~ 50•68 
Cowpea-maize 0.41 y= 0.27 SJ·44 
No-tillage 0.12 y= 0.10 1'.09 
Soil and water losses for different slopes and soil management 
~~o ~ 
The slope-soil loss relationships for first and second season maize­
maize (no-tillage) and cowpeas-maize (plowed) treatments are shown in 
Table 6.20. The erosion loss from the second season maize crop follow­
ing cowpeas was most significantly correlated with slope. The correlation 
coefficient between soil loss and slope {or the first season close-canopy 
cowpea crop was low. No-tillage treatments (1973 data) showed no rela­
tion between soil loss and slope regardless of the crop, i.c. maize or 
cowpeas. 
Table 6.20. Slope soil loss re lations f or each season for maiz&omaize (noti/lage ) 
and cowpea ·ma ize (plowed) treatments. 
Treatment Year Season Rainfall fI Equat ion 
Cowpea·maize HH2 High 0.20 ¥= om 5°·43 
(plowed) 
Low 0.19 y= 0.20 5°·32 
II High 0.25 y= 0.26 5°.71 
II Low 0.22 y= 0.15 5°·40 
1973 High 0.12 y= 0.11 5 0 .26 
Low 0.11 y= 0.22 5°·37 
" High 0.74 'f= 0.40 sO.5~ 
II Low 0.31 y= 2.11 50•41 
Maize·maize 1972 High 0.62 y= 0.23 51 .29 
(no·t i llage) 
Low 0.40 ¥= 0.23 SO.76 
II High 0.41 y= 0.02 5°.81 
1/ Low 0.16 ¥= O.OB SO.4 1 
1973 High 0.10 y= 0.05 50 .11 
I Low 0.12 y= 0.12 SQ ·11 
II High 0.25 y= 0.04 5°·20 
II Low 0.11 ¥= 0.10 SO.07 
Table 6.21. Effect of soil and crop management on soil loss 
First season Second season 
Slope Bare- Maize· Maize· Maize' • Cowpeas · BarlJ- Maize· Maize- Maize" · Cowpeas 
% fallow maize maize Cowpeas maize fallow maize maize Cowpeas maize 
(mulch I (no·til.) (mulch) Ino·til.l 
1 1.00 0.00 0.20 0.00 0.06 1.00 0.00 0.' 1 0 .00 0.19 
5 1.00 0.00 0.10 0.00 0.06 1.00 0.00 0.04 0.00 0 .08 
10 1.00 0.00 0.08 0.00 0.04 1.00 0.00 0.04 0.00 0.06 
15 1.00 0.00 0.14 0.00 0.04 1.00 0.01 0 .16 0.03 0.39 
38 Soil erosion problems on an alfisol ill Western Nigr:na 
Table 6.22. Effect of different stages of growth of maize on soil erosion. 
Growth Stages 
Treatment I 1/ !II IV 
1 1.00 1.00 1.00 1.00 
2 0.0004 0.0000 0.0001 0.0143 
3 0.2213 0.1277 0.0867 0.0214 
4 0.0027 0.0003 0.002 0.0003 
5 0.2638 0.0103 0.0003 0.0016 
(umulati ve soiHoss factors (C) for different crop rotations and soil 
management practices are ShO"l1 in Table 6.21. As expected, mulch and 
no~tillage practices has the smallest coefficients and therefore were most 
effecti ve in preventing soil loss. The effect of different growth stages of 
maize on soil loss coefficients is indicated in Table 6.22. 
CONCLUSIONS 
The following general conclusions can be drawn from the data presen~ 
ted in Chapter 6: 
(i) The exponential slope-runoff relation for bare·rallow treatments does 
not hold. The runoff losses are governed more by soil hydrological char' 
acteristics than by slope. The correlation coefficients between slope and 
runoff for no~tillage and mulched treatments are high. although the magni~ 
tude of the runoff losses under these treatments is small,. regardless of 
slope . 
(ii) The slope~soilloss relationships for bare~fallow treatments indicate 
an exponential function (correlation coeffici ent between 0.7 and 0 .9). The 
exponential relationship however, did not apply to mulching and no,t\lIage 
practices. 
(iii) Mulching and no~ti1lage treatments were most effective in preveot~ 
iog runoff and soil loss on the slopes investigated. 
REFERENCES 
Borst , H. L. and R. Woodburn , 1942. The effect of mulching and methods 
of rultivation and runoff and erosion from Muskingum silt loam. 
Agric. Eng. 23: 19-22. 
Charreau, C . • 1969. Effect of cultural techniques on runoff and erosion in 
Casamance (Senegal). Agro. Tmp. 27:905-929. 
Fournier. F . ,1967. Research on soil erosion in Africa. Afr.Soils 12.53-96. 
Harrold, L. L., 1972. Soil erosion by water as affected by reduced tillage 
Soil and water losses fOT different slopes and soil management 
practices 39 
system. Proc. no~tillage systems symposium, Feb. 21-22, 1972. The 
Ohio State lini\'. 
Hudson , 1\. W. ,195'] Erosion control research . The Rhod. Agric. J. 54: 
297-323. 
Hudson, N. W.,1964. Field measurements of accelerated soil erosion III 
localised areas. Rhod. Agric. J. 61:46-47. 
Hudson, N. W. and D. C. Jackson, 1959. Results obtained in the measure~ 
ment of erosion and runoff in Sou th em Rhodesia. Third Inter~African 
Soils Conference,Dalaba. Proceedings 2, 575-584. 
Kowal, J .,19']2. The h~' drology of a sma11 catchment basin at Samaru, 
l\igcria. IV Assessment of soil erosion under varied land manage~ 
ment and vegetation cover. Nigerian Agric. J. 7:134-147. 
\tannering, J. V. and L. D.Merer, 1961. The effects of different methods 
of com stalk residue management on runoff and erosion as evaluated 
by simulated rainfall. Soil Sci. Soc. Amer. Proc. 25:506-510. 
Mannering, J. V. and L. D. Meyer , 1963 . The effect of various rates 'of sur; 
face mulch on infiltration and erosion. Soil Sci. Soc. Amer. Proc. 
27:84-86. 
Mannering, J. V. and R. E. B\lIweU, 1968. Ti.Hage methods to reduce runoff 
and erosion in the com belt. Agric. lnr. Bull. C. S. Dept. Agr. Res. 
Servi ce 33: 14. 
Moldenhauer, W. c., W. H. Wischmeier and D. T, Parker, 1967. The influence 
of crop management on runoff, erosion and soil properties of Marshall 
silty clay loam. Soil Sci. Soc. Amer. Proc. 31::;41-546. 
Roose, E. J. , 1967. Ten years of erosion and nmoff records in Senega\. 
Agron. Trop. 22:123-152. 
WiltShire, G. R. 1947. RUnoff plots and standard runoff~ and soil;loss 
measuring equipment used by the New South Wales Soil Conservation 
Service. Soil Conservation.J. 4:40-44. 
Wischmeier. W. H. 1966. Relation of fi eld runoff to management and phr'si~ 
cal factors. Soil Sci. Soc. Amer. Proc. 30:272-277. 
Wischmeier, W. H., D. D. Smith and R. E. Uhland, 1958. Evaluation of 
factors in the soil loss equation. Agr. Eng. 39 :458-462. 
Zingg, A. W., 1940 . Degree and length of land slope as it affects soilloss 
and runoff. Agric. Eng. 21:59. 
• 7 
mulclitnG effectl on runoff 
and loll 1011 
Soil erosion is a work function inwlving detachment of soil particles 
from aggregates and transportation of the detached particles to another 
place. The energy to perform thi s work is provided by raindrop impact 
and th-e stJ.ess exerted by concentrated runoff. The stress increases 
·with slope steepness and runoff velocity. Effective control of erosJOn, 
therefore, lies in reducing the direct impact of raindrops, maintaining 
maximum soil infiltrability and decreasing the quantity, the velocity and 
the transport capacity of runoff water. These control measures can be 
achieved through residue mulches on the soil surface. 
The effects of mulching on soil and water consen'ation has been re· 
viewed by Jacks et al (1955) and McCalla et al (1962). Briggs and Boltz 
(1910) advocated using mulch and residue on the soil surface to reduce 
runoff and control wind erosion on fallowed land in arid climates. EXlen· 
sive experiments on use of mulches in soil and water conservation were 
initiated subsequently by various agencies. Duley and Kelly (1939) found 
that covering the soil surface with straw increased infiltration and pre' 
vented the formation of a thin, compacted, slowly permeable layer caused 
by raindrop impact on bare soil. Borst and Woodburn (1942 a and b) attrilJ.. 
uted the effect of mulching in reducing runoff and soil loss to increased 
surface detention and decreased rate of runoff. Taylor and Hays (1960) 
found that a heavy mulch of corn stalks and manure provided excellent 
erosion control on com following com on Fa~'ette silt loam on a 16% slope. 
Similar]y, Whitaker et al (1961) reported that a large amount of plant 
residue greatly reduced serious soil and water losses from sloping clay· 
pan soils. Meyer and Mannering (1961) found that soil loss from plots 
covered with shredded corn stalks was slightly less than one,half that 
(rom plots upon ~hich unshredded com stalks were left behind by me­
chanical com pickers. 
Mannering and Me~· er (1961) applied 6.25 inches of simulated rainfall 
at a rate of 2.5 in/hr to mulched and unmulched -plots 'on a 5% slope. The 
soil loss on the unmulched plots was 12 lQns/acre, .. ~o runoff and soil 
losses were recOIded from the plots that received mul~h at the rate of 
two IOns / acre. With one ton/acre of mulch the soil loss was' only 0.2 toni 
acre; with 0.5 ton/acre of mulch the soil loss was 1 ton/acre. Swanson 
et al (1965) reported that mulches effectively controlled erosion on a 6% 
42 Soil erosion problems on an alfisol in Western Nigeria 
slope. Adams (1966) found that straw and gravel mulch decreased runoff 
and erosion. Barnett et al (1967) reported that mulching effecti vely pro' 
tected newly seeded 40% backslopes from erosion. ln their studies Barnett 
et al found that the average runoff and soil loss for all mulch treatments 
were 17% of rainfall and 3.4 tons/acre, respectively , compared to 38% of 
rainfall and 20.2 tons/acre for the unmulched plots. 
The effectiveness of stone mulch in controlling runoff and soil loss 
has also been reported by various workers. Pebble mUlches have been 
used to conserve soil water in China (Chapman, 193/; Tsiang, 1948) and 
in South Africa (Whitemore et aI, 1953). Hide (1954) reported that evapo­
ration, runoff and erosion were reduced on a Bath Flaggy silt loam with a 
65% surface cover of stones. lung (1960) found that on eight,meter-Iong 
bare plots with 10.5% slop e , a stone cover replaced after every rain de­
creased runoff by reducing raindrop impact and sealing of upper pore 
spaces during heavy rain fall. Soil loss was prevented by the roughness 
of surface under the stone cover. 
In summary, the effect of mulches in reducing erosion can be attributed 
to. 
(i} reducing raindrop impact; 
(iO increasing soil infiltration rate by decreasing surface sealing; 
(iii) increasing sudace storage; 
(iv) decreasing runoff velocity; 
(v) improving soil structure and porosity; and 
(vi) improving the biological activity related to soil cover and its innu­
en ce on poro si ty . 
One practical way to obtain mulch is by crop,residue management 
using no-tillage or mulch,tillage techniques. Extensive work on no,tillage 
systems has been reported by various workers (Burwell et aI, 1968; 
Moldenhauer and Amemiya, 1968 ; Greb et aI , 1970; Unger et aI , 1971; and 
Harrold et a~ 19/0). 
The results of mulching experiments reported herein were conducted 
at UTA during 19/4. Runoff and soil losses from plowed plots mulched 
with 0, 2, 4 and 6 tons/ha of rice straw were compared with those from 
no,tillage p]ots on slopes ranging from 1 to 15%. No cover crops were 
grown. All plots received 120 kg/ha of N as urea and 30 kg/ha each of P 
and K. In addition to measuring soil and water ]osses, the nutrient con' 
tents of runoff water and eroded soil were also analyzed. The soil and 
water losses recorded are described below. 
Mulch Rate and Runoff Loss: The effects of mulch rate on runoff losses 
during the first and second seasons of 1974 are shown in Tables7.l and 
1.2, respective]y. There were no definite relationships between runoff and 
slope, except that the 1% slope plots had the lowest runofLlosses. Mean 
Mulching effects on runoff and soil loss 43 
Table 7.1. Effect of mu Ich rate on runoff Joss (mm ), first season 1974. 
Slope Mulch Rate (tons/hal 
% 0 2 4 6 No·tillage Mean 
1 283.2 6.0 4.2 0.0 6.4 60.0 
5 345.9 61 .2 10.1 6.: 8.9 86.6 
10 218.5 45.5 20.9 12.3 15.2 62.5 
15 294.3 46.9 20.0 12.1 14.1 71.6 
Mean 285.5 39.9 13.8 7.8 11.2 
Table 7.2. Effect of mul ch rate on runoff loss (mm l. second season 1974. 
Slope Mulch Rate (tons/ha ) 
% 0 2 4 6 No·tillage Mean 
1 128.5 30.2 2.5 0.0 5.1 33.2 
5 137.1 64.9 18.2 4.0 5.9 46.0 
10 84.4 28.3 13.8 8.8 8.8 28.8 
15 80.4 39.9 30.6 7.8 8.5 33.4 
Mean 107.6 40.8 16.3 5.1 7.1 
runoff losses during th e fi rst season were 60, 87, 63 and 72 mm for the 
1, 5, 10 and is%. slopes, respectively. During the second season, the 
corresponding losses were 33 , 46,29 and 33 mm . Mulch rate had a signifi­
cant effect on runoff. Mean runoff losses during th e first season were 286, 
40, 14 and 8 mm for plots wi th 0, 2, .. and 6 tons/ ha of straw mulch , res­
pectively . Runoff losses from the no-tillage plots were between those from 
plots mulched with 4 and 6 tons/ ha of straw. Similar results were obtained 
during th e second season. Mean runoff losses of 108, 41. 16 and 5 mm 
were recorded from the plots with 0, 2, 4 and 6 tons/ha of mulch, respec* 
tivel), . The mean runoff loss from th e no-tillage plots was 7 mm, com' 
pared to that from the plots with 6 tons/ha of mulch. 
Multiple regression analyses of runoff with slope for different rates of 
mulching are shown in Tabl e /.3. At the 0 mulch rate runoff loss was not 
couelated with slope, but the correlation coefficients improved with in­
creasing rates of surface mulch. The correlation coefficients were lower 
{or the high rainfall condi tions than for the low rai nfall conditions. The 
analyses of the runolf data based on exponential functions are shown in 
44 Soil erosion problems on an ai/isol in Western Nigeria 
Tables 7.4 and 7.S. As expected from the previous analyses. the correla­
tion coefficients relating runoff with slope improved with increasing 
mu I ch rates. 
Tabl e 7.3. Mulch rate and runoff, mUltiple regression analysis 
(a) High Rainfall 
Mulch Rate R2 Equation Average Y 
(tons/ha) % of Rainfall 
0 o:n y= 38.56 + 25.90 S - 4.75 S<+. 0.21 S3 60.8 
2 ns ns 15.4 
4 0.16 y= 1.11 + 0.48 S 4.B 
6 0.78 y= 1.12 + 0.65 S - 0.03 S2 1.7 
No-tillage 0.51 y= 1.52 - 0.24 S + O.OB 52_ 0.004 s1 2.2 
(a' Low Rainfall 
Mulch Rate ~ Equation Average 
(tonslha J % of Rainfall 
0 0.08 y= 53.5 - 1.A5 S 4'.0 
2 0.32 y= 4.12 + 4.97 S - 0.62 S2+ 0.02 S3 4.7 
4 0.34 y= 0,79 + 0.31 S 3.2 
6 0.41 Y= 1.38 + O.OB S - 0.04 52 '.9 
No-tillage 0.09 y= 1.64 + 0.24 S 3.4 
Table 7.4. Slope runoff relations for different mulch rates 
(a) High Rainfall 
Mulch rate r Equation Average Y 
(tons/hal % of Ra.infall 
0 -0.1 y= 59.2 S-0.04 55.7 
2 0.44 y= 2.1 SO.66 6.7 
4 0.76 y= 0.8 Sl.05 2.7 
6 0.89 y= 0.001 S3.3 0.58 
No-tillage 0.57 y= 1.2 sO·29 1.93 
Mulch Rate and Soil Loss: The effect of mulch rates on Soil losses for 
different slopes are shown in Figures'"}.1 and 7.2 for the first and second 
seasoo~ of 1914, respectively. Maximum soil losses during the first sea­
sons were 110, 3.5 0.5 and 0.3 ronsjha from plots mulched with 0, 2. 4 
and 6 tons/ha of rice straw, respectively. The maximum soil loss from 
the no,tiJlage plots was 0.6 loos/ha. Similar results were obtained during 
the second season (Fig. '") .2). 
Mulching effects on runoff and soil loss 45 
1000 
100 
o Ton! ha 
10 
111 
-.c 
CI! 
~ 
2 Tons/ha 
o--'  
(/)1-0 
I> " NO-TILLAGE 
.--"" 4 Tons/ha 
c 6 Tons! ha 
.10 D 
01 ~--_-_-----f!;:.--d----_----;:!::--_______- -:-! 
1 W m 
SLOPE ("I.) 
Fig. 7. Effects of mulch rate, no-tillage system and slope on soil erc· 
sion in the first season, 1974. 
46 Soil erosion problems on an al/isol in Western Nigeria 
Table 7.5. Slope· runoff relation for different mulch rates 
(Low Rainfall) 
Mulch rate r Equation Average Y 
(tons/hal % of Rainfall 
0 0.27 y= 47.5 S-0.22 33.0 
2 0.49 y= 1.5 SO.47 3.4 
4 0.73 y= 0.8 50.66 2.3 
~ 0.09 y= 0.002 53•07 0.39 
No-ti lIage 0.48 y= 1.62 5°·30 2.6 
MULCH RATE 
SECOND SEASON, H'14 
100 
o 
o o Ton/ha 
2 Tons/ha 
., " 
.s::. 
~ " 4 Tons I ha 
<II 
C 
2 
1.11 1-0 A 
1.11 
0 
oJ 
..J 
<3 
Vl 
6 Tons/ha 
10 
c 
,..-,.. NO-TILLAGE 
.-~ " 
,." 
./.,. 
SLOPE ('10) 
Fig.7.2 Effects of mulch rate, no-tillage system and slope on soil ero­
sion in the first season, 1975. 
Mulching effects on runoff and 'soil loss 41 
Multip\e regtession analyses of soil loss with slope, for both high and 
low rainfall, are given in Table /.6. As expected, a slope,soil loss rei a' 
lionship exists only for the unmulched plots and the correlation coeffi. 
cients were generally higher for high·rainfall conditions than for low, 
rainfall conditions. Under high'rainfaU conditions, the mean soil losses 
from plots mulched with 0, 2, 4 and 6 tons/ha of mulch were 143, 16, 2 
and 0.4 kg/ha/mm of rainfall, respectivel)'. Similar data for low~rainfall 
conditions were LOO, 2, 0.7 and 0.4 kg/ha/mm of rainfall. Soil losses from 
the no·tillage plots were similar to those from plots that received 6 tons! 
ha of mulch under both high and low rainfall conditions. 
The analyses based on exponential relations between soil loss and 
slope are ~iven in Tables 7.7 and 7.8 for high and low rainfall, respcc-
Table 7.6. Mulch rate and soil loss, multiple regression analysis 
(a) High Rainfall 
Mulch rate R2 Average Y 
Equation 
(tons!ha) kg/ha/mm 
0 0.44 y= ·38.8 + 51.97 S • 2.57 S2 143.1 
2 0.12 y= ·2.65 + 2.44 S 16.4 
4 ns ns 2.n 
6 0.11 y= -0.06 + 0.05 S 0.4 
No·ti Ilage ns ns 0.6 
(b \ Low Rainfall 
Mulch rate R2 Equation 
(tons/hal Average Y 
kg/ha/mm 
0 0.34 y= ·33.1 + 49.06 S - 2.93 S2 100.5 
2 0.08 y= -0.49 + 0.91 S - 0.05 S2 2.2 
4 0.15 y= ·0.75 + 0.98 S - 0.13 S2+ 0.005 S3 0.7 
6 0.12 y= -0.12 + 0.07 S 0.4 
No·tillage 0.10 y= ·0.50 + 0.65 S ~ 0.09 S + 0.003 S3 0.4 
Table 7.7. Slope - soi I los s rei ations for di fferent mulch rates 
(H i gh Rainfall) 
Mulch fate r Equation Average 
0 0.81 y= 11.8 Sl.13 76.60 
2 0.35 y= 0.5 SO.87 2.40 
4 0.57 y= 0.07 Sl.05 0.37 
6 0.46 y= 0.01 S1.0 0.09 
No·tillage 0.35 y= 0.01 SO.5 0.09 
48 Soi I erosion problems on an alfisol in ijestem Nigeria 
lively. Once again, the best fit (r =< 0.8) was obtained for the data from 
the unmulched plots. The correlation coefficients were also higher for the 
high·rainfa1t conditions than for the low. 
Wischmeier (1973) proposed using a mulch factor - the ratio of soil 
loss with mulch to corresponding loss with no mulch - to predict in the 
universal 50iHoss equation. Mulch [actors for runoff and soill05s, aver· 
aged for all slopes, ranging from I to 15% are shown In Figure 7.3. The 
mul ch factors decreased logarithmi cally wi th increasing mulch rates. The 
eHects of slope are &Iown in Figure ,.4. The mulch factors increased 
with increase in slope only for the mulch rates of 4 and 6 tonsjha and 
for the no·tillage treatments. 
10 
-- First Se"son} run ofl 
__ Second" 
0 - - --{] First seolon } IOU 
0 - - - D Soecnd " 
D 
\ 
\ 
\ 
\ 
\ 
'I ~ 
\ 
\ 
\ 
\ ~ 
'\ 
\ 
\ 
\ 
'\ 
\ 
\ 
\ 
\ 
'\ 
'\ 
\ 
\ 
,01 \ 
"-
'\ 
\ 
'0 
D 
' OO I ~O- -----""'T--------,~------r_---
taU letl rot e (tons/ha) 
Fig. 7.3 Mulch factor for runoff and soil erosion. 
Mulching effects on runoff and soil loss 49 
10 
2TONS/ha 
~ NO-TILLAGE 
............. .... -'" 4 Tons/ha 
....... '" - " 6 Tons/ha 
..... "J" ..... 
00l ·'---------~1.O,,---..j~--"":=.--b--~--------:!1OO 
SLOPE (°1.) 
Fig.7.4 Influence of degree of slope on mulch factor for soil erosion 
under different mulch rates and no-ti Ilage system. 
The mulch rate - soil loss and mulch rale - runoff relationshIps for 
diffetmt slopes art: shown in Tables J.9 and 7.10 respectively. The high 
correlation coeffici ents indi cate that exponential relationships between 
soil loss and mulch rate and between runoff and mulch rate exist for the 
mulched treatmen ts. 
CONCLUSIONS 
• Mulching with straw at a rate of 4 to 6 tons/ha effectively prevents 
runoff and soi I loss from slopes ranging from 1 to 15%. 
• The effectiveness of no-tillage treatments in preventing runoff and 
erosion is comparable to applying 4 to 6 tons/ha of straw mulch. 
• The slope-soil relationships show an exponential function for un­
mulched plots only. Slope-runoff relationships exist only for high­
mulch and no-tillage treatments. 
50 Soil erosion /Jroblems on an atfi so l in Westem Xi geria 
Tabl e 7.B. Slope-soil loss relations for different mulch rates 
Mulch rate r Equation Average 
0 0.38 y= 11.2 5°·74 38.38 
2 0.32 y= 0.3 5° ·35 0.B8 
4 0.41 y ~ 0.1 SO.53 0.27 
6 0.49 y", 0.04 5°·72 0 .14 
No-tillage 0.12 Y- " 0.13 5°·14 0.16 
Table 7.9. Mulch ing effects on soil loss under different slopes 
(Mulch Facto r) 
Slope % R Equation 
f).8S y= 0.19 M -0.54 
5 0.85 y= 1.25 M -0.71 
10 0.96 ¥= 1.09 M-0.67 
15 0.72 y= 0.98 MO.24 
Table 7.10. Mulching effects on runoff under different slopes (Mulch Factor) 
Slope % R Equation 
0.78 ¥= 0.39 M -9.73 
5 0.80 y= 1.16 M -0.36 
10 0.86 y= 5.53 M -0.27 
15 0.75 y= 5.26 M-D.55 
• \1ulch-soil loss and mulch-runoff loss relationships also show an 
exponential function with a negative exponent of mul ch rate ranging 
hetween 0.2 and 0.7 . 
REFERENCES 
1. Adams, J. 13.,1966. Influenc e of mulches on runoff erosion and soil 
moisture depletion. Soil Sci. Soc. Amer. Proc. 30: 110-114. 
2. Barnett, A. P., E. G. Disek er and E. C. Richardson, 1967. Evaluation 
of mulching methods lor erosiun con/colon newly prepared and 
seeded highway back slore . Agron. J. 59:83- 85. 
ooulcnmg et!ects on nmoff and soil loss 51 
3. Botst , H. L. and R. Woodrum, 1942a. The effect of mulching and 
methods of culti valion on runo ff and ero sion from Muskin gum 
silt loam . Agri. Eng. 23:19-22. 
4. Borst, H. L. and R. Woodburn, 1942b. Effect of mulches and surfact: 
conditions on the water relations and erosion of Musk in gum soil. 
USDA Technical Bull. S2S.76pp. 
5. Briggs, L. J. and J. O. Boltz, I910. Rainfal1 and evaporation in the 
dry farming sections of the United States. The Dry Fanning 
C'...ongress Bull'):81-87. 
6. Burwell, R. E., L. L. Sloneker and W. W. Nelson, 1968. Tillage in~ 
flunces water intake. J. Soil and Water Conserv. 23:185-187. 
7. Chapman, B. B., 1937. Climate. Chapter IV in J. L. Bu ck, ed. Land 
Utilization in China. Univ. of Chicago Press, Chicago. 
8. Duley, F. L. and L. L. Kelly, 1939. Effect of soil type, slope and 
surface conditions on intake of water. Nebraska Agri. Exp. Sta. 
Res. Bull. 112. 16pp. 
9. Greb, B. W., D. R. Smika and A. L. Black, 19JO. Water conservation 
with stubble mulch fallow. j. Soil and Water Conserv. 25:58-62. 
10. Harrold, L. L., 1972. Soi I erosion by water as affected by reduced 
tillage systems. PIOC. No~ti1lage Systems Symposium, Center 
for Tomorrow, Columbus, Ohio, Feb. 21-22, 1972. 
11. Harrold, L. L., G. B. Triplett and R. E. Youker, 1967. Watershed tests 
of no~tiIIage corn. J. Soil and Water Conserv. 22: 98-100. 
12. Harrold, L. L., G. B. Triplett and W. M. Edwards, 19JO. No~ti11age corn, 
characteristics of the system. Trans. Amer. Soc. Agric. Eng. 
51(3) 128-131. 
13. Hays , O. E., 1961. New tillage methods reduce erosion and runoff. J. 
Soil and Water Conserv. 16: 172-nS. 
14. Hide, J. C. , 1954. Observations on factors influencing the evaporation 
of soil moisture. Soil Sci. Soc. Amer. Proc. 18: 234-239. 
IS. Jacks, G. V., V. D. Baird and R. Smith, 1955. Mulching, Commonwealth 
Bureau of Soil Sci. Tech. Comm. No. 49. 
16. jung, L., 1960. The innuence Of the slone cover on runoff and erosion 
on slate soil. Int. Ass. Sci. Hydro!. Pub. 53. GelLAssembly, 
Helsinki 143-153. 
Soil erosion problems on an alfisol in Western Nigeria 
17. McCalla, T. M. and T.J. Army , 1961. Stubble mulch farming. Adv. in 
Agron. 13: 125-196 . 
18. McCalla, T. M., T. J . Army and c.J. Witfield, 1962. Stubbl e-Mulch 
Fanning. J. Soil and Water Conserv. 17: 204-208. 
19. \iannering, J. V. and L. D. Meyer, 1961. The effects of different 
methods of Com-stalk residue management on runoff and erosion 
as evaluated by simulated rainfall. Soil Sci. Soc. Amer. Proc . 
25: 506 - 510. 
20. Meyer, L. D. and J. V. Mannering, 1961. Minimum tillage for corn: its 
effect on infiltration and erosion. Agr; Eng. 42: 72-75. 
21. Meyer, L. D. and J . V. Mannering. 1967. Tillage and land modification 
for ero s ion control. Corif. Proc. Tillage for Greater Crop Produc· 
tion. A. S. A., S1. Joseph, Michigan, 58-62. 
22 . Moldenhauer, W. C. and M. Amemiya, 1968. Tillage practices for con­
trolling crop land erosion . J . Soil and Water Conserv. 24: 19-21. 
23 . Swanson , N.P., A. R. Derick, H. E. Weekly and H. R. Haise, 1965. 
Comparing mulches - Scientists check effects of four mulching 
materials on 6% slope. Agr. Res. 13(8). 
24. Taylor, R.E., and O. E. Hays, 1960. Agron. Abstr., Amer. Soc. Agron. 
P. 41. Reported in D. D. Smith and W. H. Wischmeier (1962). 
Rainfall Erosion . Adv. AgIOn. 1962: 109-146. 
25. Tsiang, T. C, 1948. Soil conservation , an international study. F.A.O. 
U.N., pp. 83- 84. 
26. \~hitaker, f . D. , V. C. Tamisan and ]. f. Thornton, 1961. Runoff 
and Erosion Lo sses hom \1exico. Silt loam in relation to ferti­
lization and oth er management practices . SoU Sci . Soc. AIDer. 
Proc. 25: 401-403. 
2/. Whi temore , J. 5. , J .N. Marais and W. H. Turpin, 1953. Weeds: Major 
men ace to crop production. Fanning in South Africa. 293-297. 
28. Wischmeier , W. H., 1973. Conservation tillage to control water erosion. 
Pmc. National Confe rence on conservation Tillage. Soil Con~ 
ser. Soc. of Amer. Ames , Iowa, 1973, 133-140. 
29. Unger, P . W. , R. R. Allen and A. F. Wiese, 1971. Tillage and herbicide 
for surface residue maintenance, weed control and water conser­
vation . J . Soil and Water Cons erv. 26: 147 - 150. 
• 8 
Rainfall ero/lvlty and 
loll ero/lon 
The role of the kinetic energy of the raindrop in soil detachment has 
long been recognized (Ellison, 1941 ; Ekern and Muckenir, 1947; Woodburn. 
1948). Ellison (1947) reported that the soil detacbm ent hazard (0) is 
directly proportional to the product of the soH "detachability ~D2) and the 
detaching capacity of the rain (D 3) and inversely proportional to the re­
sistance factor (R) of surface cove.rs and mulches in reducing runoff 
velocity (Equation 8.1). 
Dl = (DzxD3)/R ---------------------- 8.1 
Soil transport is also a work function (8.1) influenced by the rainstorm 
characteristics. For example, Ekern and Muckenbim (1947) reported that 
for a constant drop size and time, the amount of sand transported was 
directly proportional to the intensity of the preciptation and showed a 
logarithmic relationship to drop diameter as shown in Equation 8.2. 
Sand Transport = KI log d - K2 (8.2) 
Experiments conducted by Mookerjee (1950) in India showed a high "­
correlation between rainfall intensity and the amou,9t of eroded soil. Mihara 
(l953) attriooted soil erosion less to running water and more to raindrop 
impact. Ekern's (1954) findings related storm erosivity exponentially to , 
rainfall intensity. Similar results have been reported by Adams (195') and 
Tamhane et al (1959). Free (1960) reported that only lasting rain of high 
intensity combined with some packing and sealing before the rainfall 
caused runoff and soil losses. Free also reported that the rela tionship of 
ratio of infiltration to runoff with rainfall energy was exponential and of the 
hyperbolic type. Rose (1960) concluded that the rate of soil detachment 
per unit area was influenced more by the momentum than the kineti c energy 
of the storm per unit area and time. 
Wischmeier (1955) reported that the combination of rainfall energy and 
quantity of rainfall was the most important variable affecting soil erosion. 
Further analysis hy Wischmeier et a] (1958) showed that the correlations 
between both soil loss and total rainfall of individual storms and rainfall 
in 5-, 15-, or 30-minute intervals were poor. The product of the kinetic 
energy of the storm and the 3().-minute iDtensi ty (EI 30) was most signi fi­
cantly correlated wi th the soil loss. 
54 Soil erosicm problems on an alfisol in Western Nigeria 
Although the EI30 index is the best known method of c<liculaling Ihe 
erosivity of rainfall, the index has not been entirely satisfactory , partinl­
larly for tropical rainstorms. The intensity used in the El30 index is 
generally <SOmm/ hr, but storms of milch higher intensitics arc frequent in 
the tropics. Rogers et al (1967) indicated that calculating the kinetic 
energy of rainfall from rainfaJ] intensity was sarisfactory . However, this 
may not be satisfactory in the tropics where rainstorms are often prcccdro 
by high winds. Lyles et al 0969) found that wind-driven rain consiuerably 
increased soil los.s. Ahmad and Breckner (1974) found in Trinidad that 
correlations of soil loss with the E130 index were generally low. In !he 
developing countries of the tropics, characterizing thc cros;\.;ity of {he 
climate with th e El30 index presents problems, not only because of the 
technical reasons mentioned above but also because long,term rain-
gauge records are not available. Other rainfall indices have been proposed 
for use in the tropics. 
Fournier (1956) and Fournier and Henin (l959) analyzed the sediment 
load \alues ot more than 140 rivers in Europe, Asia and the UnitedStates 
and found a significant correlation between tOlal annual erosion, (ton i 
km2) and {he rainfall coefficient (Equation 8.3). 
C = p2/p (8.3) 
p is the monthly rainfall during the wettest month of the year and P is the 
annual rai n fall. 
The soil loss or "spccifi c degradation", was expressed as Equation 
8.4. 
o ~ aC-b (8,4) 
o is the speci fie degradation or soil loss and a, b arc coefficicn ts whose 
magnitudes dcpend upon the orographic coefficient (0) of Equation 8.S. 
(0) = H 2/ S (8.5) 
H is the height of the terrain above its base level and S is its projected 
area. 
Foumi er' s index was more si gnifi cantly correlated wi th erosion in the 
tropics than in th e tcmperate climatc and with steeper than with gentler 
slopes. This climatic index is useful for large watersheds. Howevcr, for 
small areas the erosivity of the climate, parlicularly in relation to soil 
management, cannot be easily predi cted with this index. 
Hudson (19']1) reported from his work in Rhodesia that !he cumulative 
kinetic energy of storms with intensities greatcr than 1 inchlhr (KEil) 
was more significantly correlated with soil loss than the EJ 30 index. 
Roose (1973) found from data collected in the Ivory Coast that climatic 
erosivity was significantly related to quantity of rainfall. His analysis 
indicated an cxponential relationship between the El30 index and rainfall 
Rainfall Erosivity and soil erosion 55 
amount in the humid-forest region of the Ivory Coast and a linear relation­
ship in the savanna region. 
Calculations of the Rainfall Erosivity in Relation to Runoff and Soil Loss 
The work reported here was conducted at I1TA during 1972 - 1974. 
Hainfall intensity records were obtained for each storm using an automatic 
daily recording rain gauge (Bclfort lnst. Model 5-780). The kinetic energy 
of the rainstonn was calculated by the relations described by Wischmeier 
ct al (1958), using Equation 8.6. 
Kinetic energy (foot-tons/ acre) = 916 + 331 log10 I (inches / hour) 
The kinetic energy thus calculated was multiplied by the greatest average 
intensity recorded during 7.5-, 15-, 22.5-, 30· , 37,5- an~ 45-minute inter­
"Jls. The products were termed DU.S, EllS EI22.5, El30, ElY].5,and 
E'45 ' Each was multiplied by the tot~l amount o! rain re~eived (A).The 
nc''> indices were designated AEI, With appropnate suffixes to denote 
time intervals. The erosivity of each stonn was also calculated with 
Hudson ' s KE>l index. Simple conelations were then computed between 
soil and water losses from bare- fallow plots and rainfall amount (A), rain­
.fal~ intensities (1 . to (45). EI indices (EI
7 5 / .S to EI4,») and AI andAEI 
 
mdlces. 
RelationsHips Between Rainfall Amount and Runoff and Soil Lass from 
Different Slopes: 
Tables 8.1,8.2 and 8.3 show correlation coefficients and linear regres­
sion equations relating runoff and soil loss to rainfall amount, runoff to 
~il loss for each slope, runoff from a 5% slope to runoff and soil loss 
from other slopes, and soil loss from a 5% slope to soil loss from other 
slopes. 
Fairly good estimates of water runoff can be obtained from rainfall 
data for · bare-fallow plots. That the runoff-rai nfall relationship exists and 
can be used to extrapolate results is further strengthened by the high 
values of the correlation coefficients. Similarly, it seems possible to 
obtain information on water runoff for different slopes from the runoff 
lecords on one of the slopes. Furthermore, the correlation coefficients 
between water runoff from 5% slopes and that from other slopes are high. 
The leiationships between runoff and soil loss, although good, may not 
always make it possible to estimate soil los!> from runoff data alone. The 
conelation coefficients between runoff and soil loss within each slope are 
110t high. However, estimates of soil loss from water runoff from a repre­
sentative slope (a 5% slope, foi:' example) may be obtained from the re~ 
gression equations given in the tables. 
56 Soi l erosion problems on an alllsot •.• '" 
Tabl e 8. t gi yes correl arion coefficients and linear regression equa­
, tions relating runoff and soil loss from bare-fallow plots to amount of 
rainfall and relating runoff and soil loss from one slop e to that from other 
slopes (1972). 
Table 8.1 Correlation coefficient and linear regression equations for runoff and 
soil loss from bare fallow with amount of rainfall and relating runoff 
and soil loss from one slope to that of others (1972). 
Ind. Variable Dept. Variable Equation 
Amount of ra infall per stonn (A) Runoff 1% (W) 0.66 W= 6.6A + 9.2 
Amount of rainfall per storm (A) Runoff 5% (W) 0.54 W=6.8A+17.0 
Amount of rainfall per storm (Al Runoff 10% (W) 0.62 ~::7.0A+14.4 
Amount of rainfall per storm (A) Runoff 15% (W) 0.65 W= 6.SA + B.O 
Amount of rainfall per storm (Al Soil loss 1% (E) 0.94 E :: 0.09A - 0.05 
Amount of rainfall per storm (A) Soil loss 5% (E) 0.72 E = O.4BA + 0.27 
Amount of rainfall per storm (Al Soil loss 10% (E) 0.52 E :: O.52A + 0.65 
Amount of ra infa II per storm (A) Soil loss 15% (E) 0.86 E :: 2.53A - 1 .59 
Runoff 5% (W s ) Runoff 1'JE (W) 0.82 W= O.64Ws+ 0.03 
Runoff 5% (1\'5 1 Runoff 10% (W) 0.81 W= O.72W s+O.06 
Runoff 5% (W s) Runoff 15% (W) 0.74 W= O .62W 5 + 0.03 
Soil 10ss.5% (Es) Soil loss 1'JE (E) 0.80 E = 0.11 E 5- 0.008 
Soil loss 5% (Es) Soil loss 10% (E) 0.85 E = 1.29Es -+ 0.12 
Soil loss 5% (Es) Soil loss 15% (E) 0.81 E = 3.S3er.- 0.96 
Runoff 1%  ( W, ) Soil loss 1% (E) 0.81 E = 0.nWl·-0.04 
Runoff 5% (W 5) Soil loss 5% (E) 0.81 E = 4.20W 5·- 0.07 
Runoff 10'lE (W'o) Soil loss 10% (E) 0.60 E = 5.23 W'O .. + 0.20 
Runoff 15% (W ' 5 l Soil loss 15% (E) 0.70 E = 19.30Wls*-O.73 
Runoff 5~ (W 6 ) Soil loss 1% (E) 0.69 E = O.51Ws• - 0.02 
Runoff 5% (W 5 ) Soil loss 10% (E) 0.65 E = 5.03Ws- + 0.15 
Runoff 5% (Ws) Soil loss 15% (E) 0.57 E = 13.07Ws"-0.53 
Rafnfsll:: em pflr storm 
·Runoff :: fraction of tm rainf." 
Soif (0. ." " tlltll/storm 
Runoff ::: pm-cent of 'lIinfBlI 
Computation of Erosivity Indices from Rainfall Amount: 
Roose (9/3) attempted to compute the EI30 index from rainfall data . 
He round a linear correlation between rainfall amount and the EI30 index 
fOr the S'avanna region of the Ivory Coast and a logarithmic relation 
between rainfall amount at the El30 index fOI the humid-forest zone. The 
correlation cocffi ci ent and regression equations for compucing kinetic 
energy (E) and t~e EI30 and KE>l indices from rainfall amount are shown 
in Table 8.4. H igb correlation coefficients between rainfall amount and 
the various indic es for all the three years indicate that a linear relation­
ship exists and' that it is poss ible to predict eroSivity from rainfall amount. 
Rainfall Erosivity and soil erosion 57 
Table 8.2 Correlation coefficient and linea r regression equations for runoff and 
soil loss from 001'& fallow plots w.ith amount of rainfall and retating 
runoff and soil loss from one slope to that of others (1973). 
Ind. Variable Dep. Variable Equation 
Amount of rain per stonn (A) Runoff 1%  I W} 0.26 W -= 1 .9SA + 33.0 
Amount of rai n per storm (A) Runoff 5% (WI 0.21 W = l.88A + 37.0 
Amount of rain per storm (A 1 Runoff lO%(WI 0.23 W=  1.96A t- 34.0 
Amount of rain per storm (Al Runoff 15% (WI 0.27 W=2.73A + 28.9 
Amounttlf rain per stonn(A) Soil loss 1% IE) 0.94 E=O.13A 0.07 
Amount of rain per storm (Al Soil loss 5% (El 0.20 E= 0.21A + 0.30 
Amount of rain per storm (Al Soil loss 10"(E) 0.91 ~= 2.13A • 0.34 
Amount of rain per stonn (Al Soil loss 15" (E) 0.79 E= 2.11A • 0.47 
Runoff 5% (W&) Runoff ," (Wl D.n W= 0.67W5" 0.09 
Runoff 5% l~) Runoff 10% IW} o.n W= 0.74W~ +0.08 
Runoff 5% IWs) Runoff 15%(WI 0.79 W=  0.91 Wf, 4 0.02 
Soil loss 5~ (£5) Soil loss '" (E) 0.20 E =0 .03£ 5 .. 0.16 
SoH loss 5% (Es) Soil loss 10% (E) 0.3'1 E= O.7OE~ ... 2.62 
Soil loss 5% (E5) Soil loss l~(E) 0.29 E= O.nEs ... 2.21 
Runoff 1%(.11 Soil loss 1%' (E) 0.30 E= O.53W!· 0.06 
Runoff 5% (Wi) Soi I loss 5% (EI 0.60 E = 6.96"5 -..0.64 
Runoff '0" (~. Soli loss 10"(E) 0.42 E=1,;43W,o'" + 0.70 
Rt,Jnoff 15 % (W i; -') Soil loss 15" (E) 0.55 E=14.20W 15 .. + 0.17 
Runoff 5" 1"51 Soil 'oss'" IE) 0.24 E= O.36Vh;* + 0.10 
Runoff 5% (.oS} Soil loss '0" IEl 0.33 E::;: 8 .73Ws" + 1.46 
R\II\Off 5% ~'51 Soil loss 15%(E) 0.39 E:; 11.63Ws. .. 0.01 
RIJin'.1I = cmper storm 
• Runoff - fraction of rllintall 
$oilloss " tonlha/storm 
fainfall = petclNlt of fa; ntltll 
The Relation ship Between Runoff and Erosivity 'ndice s: 
Simple correlation coeffi ci ents relating water runoff from bare,fallow 
plots to the valious indices are shown in Tables 8.S, 8.6 and 8.7 for 1972, 
1973 and 1974 respecti vely. In general , runoff was significan tly corr elated 
with total rainfall of a given storm. Th e kin etic energy of th e rainsloIlTl , 
although signifi cantly correlated, was not as highly correlated with runoff 
as the total amount of rainfall during a given stollll.The various EI indices 
correlate fairly well with wa ter mnoff. Among the AI indices, the highest 
correlation was obtained with AI7.5. AEl indices were no t as highly- cor' 
related as the Al indi ces . 
58 Soil erosi an probl ems on an alfi sol in Western Ni g eria 
Table 8.3 Correlation coefficiE!1t and . linear regression 6:iuations for runoff ~nd 
soil loss from bare f.allow plots with amount of rainfall and relating 
runoff and soil loss from one slope to that of from others (1974 ). 
Inct. Variable Dep. Variable Equation 
Amount of rain per storm ~A) Runoff 1% (W) 0.15 W= 1.90A - 4.28 
Amount of rain ~er stO!1l\ (A) Runoff 5% (WI 0.21 W ~ 3.2'A - 4.72 
Amount of rain per storm (AI Runoff 10% (W) 0.07 W ~ O.76A ·34.8 
Amount of rain per storm (A I Runoff 15% (W) 0.56 W- B.50A - 12.83 
Amount of rain per storm (A) Soil loss 1% (E) 0.59 E ~ 0.12A ~ 0.02 
Amount of rain per storm (AI Soil loss 5% (E) 0.72 E = U6A - 0.02 
Amount of rain per storm IA) Soil loss 10% (E) 0.68 E ~ 2.JOA - , .32 
Amount of rain per storm IA) Soil 1655 15% (E) 0.71 E ~ 1. 78A - 1.42 
Runoff 5% (W s)· Runoff 1% (W) 0.82 W=O.66W s+0.l1 
Runoff 5% (Ws) Runoff 10% IW) 0.64 w= O.44W , + 0.12 
Runoff 5% \Ws} Runoff 1S % \ W) 0.62 W=O.62W s+O.m 
Soil loss 5%(Es) Soil loss 1% IE} 0.59 E = O.05E ~ + O. " 
Soil loss 5% (Es1 Soi l loss 10% IE) 0.91 E = 1.26E 5 -1 .09 
Soil loss 5% (Esl Soil loss 15% IE) 0.70 E = O.72E -0.05 
Runoff 1% (W,) Soil loss 1% IE} 0.56 E = O.B9W,"...o. 10 
Runoff 5% \W s) Soil loss 5% tEl 0.46 E =7.27W5"+O.S8 
Runoff 10% (W 10) Soil loss 10% IE) 0.37 E = 12.00W,04+-0.36 
Runoff 15% (W,s) Soil loss 15% IE) 0.73 E = 12.00W,~·-0.93 
Runoff 5% (W s) Soil loss 1% IE) 0.56 E =O.72W. " - 0.07 
Runoff 5% (W 5) Soil loss 10% IE) 0.47 E = 10.27W5 • -0.96 
Runoff 5% tW~) Soil loss 15% IE] 0.39 E = 6.31W 5 • - 0.22 
RBinfall ... em per storm 
" Runoff ::= frBction of ,Bin'BII 
So il loss ::= fon/nal slorm 
Runoff ::= percenr of rainfa ll 
The Rel£llion ship Between Soil Lo ss cmd Ero sivity Indi ces : 
Correlation coefficients relating soil loss from bare~fallow plots during 
individual stonns to various erosivity indices are shown in Tables 8. 8, 
8.9 and 8.10 for 1971, 1973 and 1974 respectively . The correlation co ef~ 
fici ents between soil loss and tbevariou s indices are generally lower than 
those between water runoff and the indices. Again, th e total amount of 
rainfall during a given storm correlated fairly we ll with soil Joss from all 
slopes investigated. Mean intens i ty durin g a 45~minute period (145) was 
more highly correlated wilh soil 1088 than with e ither total kin e tic energy 
o{ the storm 01 th e. El30 index. The best estimate of soil loss during an 
individual stonn was obtained with AI7 . 5. Th e weighted~m ean average 
correlation coefficients between runoff and soil loss and the variou s 
indices for all the slopes are shown in Table 8. U. Soil lo s s is gen erally 
poorly correlated with any of the variables listed. 
Rainfall Erosivity and soil erosion 59 
Table 8.4 Corre lation coeffi cients and regression equations relating rainfall 
amount A "'itn various e rosivi ty indices. 
Year Ind. Variable Dep. Vari abl e Equation 
1972 Rainfall amount E 0.97 E = 396.2 A • 112.0 
per storm 
El30 0.87 E130~ 164D.5 A - 1968.5 
KE ::> 1 0.88 KE > 1 " 362.5 A - 160,0 
" AIm 0.97 AIm =13.77 A -11.3 
1973 E 0.99 E =367 .0A-7.7 
EI 30 0.93 E130 = 254.9 A - 22.3 
" KE > I 0.88 KE > 1 = 853.0 A - 55!i .6 
Aim 0.92 AIm"" 9.22 A - 4.2 
1914 E 0.84 E = 390.6 A - 77.4 
EI30 0.78 EI30 = 215.5 A + 39.2 
KE > 1 0.79 KE > 1 = 839.5 A - 813. 7 
AIm 0.88 AIm = 9.74 A - 7.3 
1972 - 1974 " E 0.95 E = 379.6 A - 54.0 
EI30 0.87 E 130 = 273.8 A - 56.5 
KE > 1 0.82 KE > 1 = 1047.9 - 1058.4 
AIm 0.92 A l - 10.42 A • 6.9 
E faat • ton per acre KE > 1 = foot-IOn p er acre 
EI30 = foor - ton per acre Alm Cm 2ihr A ~ em 
Tabl e 8.5. Correlation coefficient (r) of run-affat differen t slopes ( ~with various 
in dices (1972) 
Variable 1% 5% 10% 75% 
17.5 0.44 0.43 0.39 0.38 
115 0.68 0.l'9 0.67 0.70 
122.!> 0.75 0.75 0.75 0.78 
130 0.81 0.81 (l.80 0.33 
137.5 0.86 G.BS 0.B5 0.B7 
145 0.87 0.87 0.87 0.8'3 
E17.5 0.85 1).79 0.82 0.86 
El lS 0.85 0.78 0.80 0.85 
El22.5 0.85 0.78 0.80 0.85 
E137.5 D.B5 0.78 0.80 0.83 
E145 0.85 0.78 0.80 0.84 
60 Soil erosion problems on an al/isol in Western Nigeria 
Table B.6. Co rrel a1ion co effi c i en t (r 1 of run-off a1 different s'opes with 
erosivity indices (1973). 
Variable 1% 5% lC176 15% 
~5 0.7J) 0.75 0.B2 0.74 
'22.5 0.84 0,85 O.SO 0.81 
'30 0.89 O.SCJ 0.92 0.85 
'37.5 0.87 0.89 O.SO 0.81 
145 0.91 0,91 0.93 0.88 
E17.5 0.90 0.90 0.95 0.88 
EI 15 0.92 0.91 0.95 0.89 
E122.5 0.92 0.91 0.94 0.89 
E1 37•5 0.93 0.93 0.95 0.88 
EI45 0.93 0.91 0.80 0.80 
Table 8.7. Correlation coefficient! r) of run-off at different slopes (1%) 
with various erosivity indices (1974). 
Variable 1% 5% 10% 75% 
115 0.75 0.78 0.65 0.75 
'22.5 0.77 0.79 0.68 0.75 
'30 O.Bl 0.84 0.74 O.SO 
'37.5 0.79 0.81 0.71 0.75 
i 45 0~86 0.89 0.78 0.86 
E1 7•5 0.78 0.85 0.71 0.7~ 
EI 15 0.75 0.81 0.67 0.77 
E1 22•5 0.73 0.79 0.G7 0.74 
E1 37 .5 0.76 0.81 0.70 0.78 
EI45 0.79 0.84 0.74 0.81 
\ New Erosiuiry Index (A1M). 
The applicability of the E130 index under tropical conditions needs 
further analysis. The parameters used for computing the EI30 index are 
kinetic energy (E) and maximum 30~minute intensity (130)' The empirical 
bases for calculating kinetic energy of a stonn seriously limits the appli~ 
cability of E[30 for determining erosi vi ty of tropi cal stonn s. Raindrop-size 
distribution and wind velocity associated with tropical rainstorms can 
cause enOl in computing kinetic energy. The kinetic energy values that 
WischmeicLcalculated with this formula are therefore under~estimated, It 
Rainfall Erosivity and 'soil erosion 61 
Table 8.8. Correlation coefficient (r) of soil loss at different slopes (1%) 
with various erosivity indices (1972). 
Variabfe 1% 5% 10% 15% 
1'5 0.79 0.64 0.55 0.67 
122.5 0.82 0.66 0.57 0.76 
130 0.85 0.69 0.59 0.83 
137 .5 0.87 0.72 0.60 0.86 
145 0.88 0.72 0.61 0.89 
E1 7.5 0.77 0.55 0.4-5 U.91 
EI 15 0.76 0.53 0.44 0.90 
E1 22•5 0.76 0.53 0.43 0.90 
E~7.5 0.76 0.53 0.43 0.89 
E145 .. 0.76 0.53 0.43 0.89 
Table 8.9. Correlation coefficient (r) of soil loss at different slop ( % ~ 
with various erosivity indices (1973). 
Vadable 1% 5% T(IX 15% 
1,5 0.60 0.20 0.79 0.66 
122•5 0.70 0.22 0.81 0.69 
130 0.75 0.26 D.Sl 0.73 
137•5 0.70 0.31 0.77 0.65 
'45 0.77 0.28 0.82 0.75 
EI 0.73 0.19 0.85 0.76 
E1 7•5 
15 0.75 0.18 0.83 0.78 
£1 0.76 0.16 0.80 0.77 
22.5 • 
El37.5 0.74 0.20 0.78 0.73 
EI45 0.78 0.17 0.80 0.80 
has been shown that an 8 mph wind can increase the kinetic energy of a 
rainstonn by 30%. Th e low correlation coefficients between soil loss and 
erosivity indices that include E may be attributed to these limitations. 
There is an urgent need to monitor the kineti c energy of tropical rain­
storms and to develop empirical relationships involving parameters of 
intensity. drop~size distribution and wind velocity. 
62 Soil erosion problems on an alfisol in Western Nigena 
Table 8. TO. Correlation coefficient (r) of soil loss a1 different slopes 
(1%1 with various erOSivity indices (1974). 
Variable 1% 5% rOOd, 15% 
'15 0.72 0.79 0.62 0.65 
122•5 0.63 0.69 0.54 0.63 
'30 0.68 0.69 0.51 0.57 
137 •5 0.56 0.48 0.51 0.55 
'45 0.67 0.64 0.53 0.66 
E1 7•5 0.75 0.76 0.59 0.66 
EllS 0.64 0.73 0.48 0.66 
E1 22•5 0.56 0.64 0.42 0.63 
E~7.5 0.57 0.61 0.40 0.5~ 
E~5 0.59 0.59 0.41 0.58 
Table 8.11 Correlation coeffici ents of various erosivity indices with 
runoff and soil loss. 
Year Erosivity Runoff Soil loss 
Index 1% 5% 10% 15% 1% 5% 10% 15% 
1972 A 0.66 0.54 0.62 0.64 0.94 0.72 0.52 0.86 
E 0.57 0.50 0.53 0.60 0.91 0.71 0.50 0.92 
B30 0.37 0.27 0.33 0.41 0.75 0.53 0.34 0.87 
AIm 0.61 0.43 0.55 0.56 0.90 0.61 0.81 0.84 
KE >l 0.38 0.33 0.36 0.47 0.77 0.57 0.37 0.85 
Im 0.68 0.51 0.60 0.66 0.82 0 .59 0.46 0.67 
1973 A 0.26 0.21 0.23 0.27 0.94 0.20 0.91 0.79 
E 0.30 0.24 0.29 0.31 0.93 0.21 0.93 0.81 
EI30 0.37 0.30 0.38 0.36 0.82 0.14 0.86 0.81 
AIm 0.30 0.19 0.31 0.31 0.86 0.11 0.88 0.77 
KE > 1 0.38 0.30 0.40 0.39 0.87 0.20 0.91 0.83 
1m 0.39 0.23 0.49 0.42 0.37 0.13 0.51 0.44 
1974 A 0.15 0.21 0.07 0.56 0.59 0.72 0.68 0.71 
E 0.23 0.33 0.16 0.63 0.65 0.B7 0.88 0.75 
EI30 0.27 0.36 0.20 0.67 0.64 0.89 0.91 0.82 
AIm 0.26 0.34 0.11 0.62 0.70 0.86 0.85 0.81 
KE> 1 0.37 0.42 0.11 0.12 0.52 0.79 0.74 0.93 
1m 0.34 0.42 0.16 0.54 0.60 0.68 0.68 0.65 
Rainfall Erosivity and soil erosion 63 
The intensity parameter of tile EI30 index also needs critical appraisal. 
The intensity of a temperate rainstonn rarely exceeds SO mm/hr. Rain· 
storms of much higher intensi ti es are frequent in the tropics, howevel, and 
intensities exceeding 100 mmjhr are n:>t uncommon. A third factor that can 
influence the effectiveness of the EI.30index is the direction of the storm 
in relation to the direction of the slope. This parameter is particularly 
important on steeper slopes. Soil creep, the detachment and subsequent 
movement of soil do\\nslope, can be significantly affected by the resolu­
tion of the impact momentum vector of the raindrop into its components. 
A fourth factor is socio-economic. The calculations involved in the El30 
index are cumbersome and skilled technicians and computer facilities 
arc needed for correct and speedy calculations. Lack of such facilities 
and talent is a problem in many developing countries of the tropics. 
The AIm index, the product of the maximum inten si ty (1m) in cm/hr ~nd 
total rainfall (A) in em has advantages over the EI indices. First, the 
Aim index includes maximum intensity, an important factor in tropical 
rainstorms. It also includes total rainfall which takes into account the 
fact that a very intense stoon that lasts only a short period and that results 
in low total rainfall is usually non-erosi Ve. As pointed out in Chapter 5, 
slope-soil loss relationships are significant only for storms with more 
than 25 mm of rainfall. 
Combining these two important parameters, maximum intensity and 
total rainfall, in one index provides a more accurate indication of rain· 
storm erosivity than using either of the parameters alone. Another ad­
vantage of the AIm index is that it is simple to compute. 
The AIm index is delinitely not the ultimate index, rut should prove 
useful until something better comes along. The Aim index, for example, 
can be improved further by incorporating a wind velocity factor that will 
reflect th~ kin etic energy of a windy storm. 
The weighted·mean average correlation coefficients for all slopes and 
all years between runoff and soil loss and the KE> I, E130 and AIm erosiv­
ity indices are shown in Table 8.12. The AIm index is more highly corre­
lated with water runoff and soil loss than the other indices. 
Preparation of Erosi vily Maps [rom the Index: 
The AIm erosi vi ty index is defined as: 
1 k 
AIm = :t [I aim) / 100 
1 1 
In thi s index, a is the amount of rain in indi vidual stonn, 1m is the m axi­
mum intensity of th e individual storm, f< is 31 and I is 12. It is the sum­
mation of the product ai over all the rainy days in a year. If a is in cm 
and i in ern/ hr, the unit of AIm is on2/hr. AIm is usu;lllv 1. - ' -- - ~., 1 and 
64 Soil erosion problems on an alfisol in Western Ni g eria 
Table 8.12 Weighted Mean Average Correlation Coefficient (r) of ' Various 
ErosivitY Indices with Runoff and Soil Loss from 10% Slope 
Plot ~ith Barefal lov., Treatment. 
Erosivity Index Runoff Soil Loss 
KE > 1 0.32 0.60 
EI 30 0.34 0.65 
AIm 0.37 0.69 
10 for areas wi th annual rainfall up to 1000 mm, between 1 and 20 for areas 
thal recei ve 1000 to 2000 mm of annual rainfall. and betwecn 1 and 30 for 
arcas that receive 2000 to 3000mm of annual rainfall . Monthl~' AIm indices 
for lbadan during 1971, 1973 and 19]4 are shown in Figure 8.1. The slope 
of the curve reflects erosivity during a given month or during any period 
in the year. 
AIM indi ces for a region connecting different ecological zones can be 
similarly plotted (Fig. 8.2). Such erosivity maps can help in designing 
T 
)( 1973 
~974 
6 1972 
1: 
'" 5 
E 
~ 
:I: 
'< 4 
~'-~~~--~A~--~M--~J~--+J--~A~--~S---70'--'N~~D 
MONTH 
Fig.8.1 Cumulative distribution of erosivity index Aim from Ibadan. 
If one does not divi~e the R.H.S. of Aim equation, the numerical 
value of Aim (em Ihr) and E!JO (foot·ton5 pt:!r acre--inch) are 
identical. Hence it does not matter how K factor is computed by 
either by Arm or E130. 
Rainfall Erosivit)· and soil erosion 65 
erosiOD,conlroJ practices as well as in pJanning agricultural operations 
and developing soil and crop-management techniques suited to a given 
location. 
Fig. 8.2 A hypot'hetical iso-erodent map for West Africa. 
900 
850 
eoo 
1973 
750 
100 
~ 650 
~ 
~ 600 
~ 550 1974-
5500 
i 1972 
~ 450 
-4 
'~"  350 
~ 
~ 300 
a: 
1: 250 
Ui 200 
150 
100 
50 
0 F A M J J A s o N o 
TIME ( Month) 
Fig. 8.3 Cumulative distribution of EI30 index for Ibadan. 
66 Soil erosian problems on an alfisol in Wesiern Nigeria 
3€0 
340 0---0 197'] 
x-- - x '97:) 
320 
6 - --6 19"'4. 
300 
280 
260 
.~ 
~ 2 40~ 
~ : 
~ nOr 
a 
c 100 
E 
, ISG 
OS 
~ 160 
~ 14 0 
c 
~ 120 
~ 100 
~ 
iii !!O 
60 
40 
20 
o F A N D 
TIME ( Month ) 
Fig.8.4 Monthly distribution of EI30 index for Ibadan. 
80 
70 
60 
"!J~*  
Q 
~ (~ 
u 
r 50 0 
ei ~<. :J' 
'-
~ ~,c:§l~ " 
I 
-0 I..'<..\-§:l 
40 
~ c:JC. >j'i 
~ 
0 
~,,~ 
~ 
""- 30 <!l 
~ (!) 
w 
0 
20 
0 GO 
0 ~ 
20 30 40 50 60 70 80 
AIm (cm2 I hr) 
Fig . 8.5 Relationship between (EI30/100) in foot-ton/acre and Aim 
(cm2/hr) for individual stOIlTt. 
Rainfall Erosivity and soil erosion 6J 
Table 8.13. Computa t ioll of Almand EIJOi ndex for a rainstorm on 16th J une, 1972. E=(foot· 
ton peraereineh l = 916 + 331 109, 0 I (\o\here I ," inch! hr.l 
2 3 4 5 6 7 8 9 
Time Ra i nfa ll AmoUn1 Ra infa ll Intensity aim Log 1331 Log I E Tota l E 
Interval inch. em. in/hr em! llr {eml hrl (in! hr ) (9)( 2) 
7.5 0.75 1.91 6.0 15.24 29.11 0.778 257.5 1173.5 880.1 
7.5 0.65 , .65 5.2 13.21 21 .26 0.716 236 .9 1152.9 749.9 
7.5 0.55 1,40 4.4 11.18 15.65 0.643 212.8 1128.8 620.8 
7.5 0 .45 1.14 3.6 9.14 10.42 0.556 184.0 1100.0 495.0 
7.5 0.25. 0.64 2.0 5.08 3.25 0.301 99.6 101 5 .6 253.9 
7.5 0.55 1.40 4.4 11.18 15.65 0.643 212.8 1128.8 620.8 
7.5 0.15 0.38 1.2 3.05 1.16 0.079 26.1 942.1 141.3 
7.5 0.30 0.76 2.4 6.10 4.64 0.380 125,8 1041.8 312.5 
7.5 0.20 ~ 0.51 1.6 4.06 2.07 0.204 67.5 983.5 196.1 
7.5 0.25 0.64 2.0 5.08 3.25 0.301 99 .6 101 5.6 253.9 
7.5 0.05 0.13 0.4 1.02 0 .13 0.398 .197 .7 784.3 39.2 
AI",= I aim = 106.59 
AI", as obtained from peak ;" tens ity and lotal rain fall amount = 160.93 
Total £ = 4563.17 
'30 (Max imum intensity in 30 minutes) " 4.8 in/hr. 
£130 / 100 = 14563. 17 x 4.8)1100 = 219.03 
Another way to compute the Aim index, which may improve the corre~ 
lation coefficient between the AIm and soil erosion, is to divide a raiD' 
storm into different intensity classes and to multiply the amount of rain~ 
fall in each cla:ss by its intensity. A weighted mean AIm index is then 
obtained by summing the products for each intensity class. 
An example of computing the ¥i eighted~ean AIm and the EI30 indie es 
is shown in Table 8.13. As expected, the numerical value of the AIm 
obtained by this method is IO¥ier dIan dIat computed from a single peak 
intensity value. 
Soi I erosi an problems on an alfisol in It't;>stem Nig eria 
05 
cr---Q 10(" SLOPE PLOT 
~ 5·'. SLOPE PLOT 
~ 10% SLOPE PLOT 
~ 15°/. SLOPE PLOT 
04 
... 0·3 
, ..- ~--
>- ~ 
~ '" 
m-l  
a 
0 
0:: 
LU 
-l 
(5 
r.J> 02 
" "-
" , , , 
01 \ 
, , , , , 
\. , ,,  
1 2 3 4 
TIME AFTER FOREST CLEARING (years) 
Fig. B.6 Changes in soil erodibility factor (k) with time after forest 
clearing. 
The distribution of the EI30 index and its relation to AIm is shown in 
Figs. 8.3 - 8.5. When AIm is not divided by 100, it is numerically identi­
cal to EI30' Therefore, K factor does not alter significantly by using 
eitheI of the two indices (Fig. 8.6). 
Rainfall Erosivity and soil erosion 69 
REFERENCES 
1. Adams,J . E ., 1957. A rainfall simulator and e.rodibility of some. Iowa 
soils. Iowa St. Coli. J. Sci. 31: 347-348. 
2. Ahmad, N., and E. Breckncr , 1974. Soil erosion on three Tobago soils. 
Trop. Agric. 51 : 313-324. 
3. Bruce-Okine, E., and R. Lal , 1975. Soil erodibilit)" as detennined by 
raindrop technique. Soil Sci. 119 (2) : }49-157. 
4. Ekern, P. C., 1954. Rainfall intensity as a measure of stonn erosivity. 
Proc. Soil Sci. Soc. Amer. 18: 212-216. 
5. Ekern, P. C. and R. J . Muekenhim, 1947. Water drop impact as a force 
in transporting sand. Proc. Soil Sci. Soc. Amer. 12: 441-444. 
6. Ellison W. V.,1947. Soil erosion studies: Part 1. Agric. Eng. 28: 
145-146. 
7. Fournier, F., 1956. The effect of climatic factors on soil erosion. 
Estimates of solids transported in suspension in runoff. Ass. 
Int. Hydrol. Pub. 38 : 6. 
8. Fournier, F. and S. Henin., 1959. A new climatic fonnula for evaluating 
the specific degradation of soils. C. R. Acad. Sci. , Paris. 248: 
1694-1696. 
9. Free, G. R., 1960. Erosion characteristics of rainfall. Aglie. Eng. 
Mich. 41: 447-449, 455. 
10. Hudson, N. W. ,1971. Soil conservation. Batsford, London, 1971. 
U. Lyles, L., L. A. Disrud and N. P. Woodruff, 1969. Effect of soil physi, 
cal properti es, rainfall characteri sti cs and wind velo city on clod 
disintegration by simulated rainfall. Proc. Soil Sci. Soc. Amer. 
33: 302~306. 
12. Mihara, Y., 1953. Effects of raindrop and glass on soil erosion. Proc. 
Sixth Int. Grassl. Congl. 1953: 987-990. 
13. Mookerjee, D., 1950. Anti-soil erosion equipment at Arabari , West 
Bengal. Cent. Bd. Inig. J. 7 : 191-193. 
JO Soil erosion probl ems on an alfisol in We stem /II igeri a 
14. Rogers,J.S., L.C. Johnson,D.M.A. Jones and B.A. Jones,1967 
Sources of error in calculating the kinetic energy of rainfall . 
J. Soil and Water Consen'. 22 (4): 140~14}. 
15. [(oose, E.]., 1973. Dix~sepl annees de mesures experimentales de 
I'erosion et du ruissellem ent sur un sol ferrallitique sableux de 
basse Cote d'l voice. Contribution a J'ctude de I' erosion hydrique 
en milieu intertropical. ORSTOM , Adiopodoume 125 p. These , 
Abidjan, ~. 20. 
16. Rose, E. E., 1960. Soil detachment caused by rainfall. Soil Sci. 89: 
28~35. 
1/. Tamhane , R. V., T. D. Biswas and B. Das, 1959. Effect of intensity of 
rainfall on soil loss and runoff. J .Indian Soc. Soil Sci. 7:23hD8. 
18. Wischmeier, W. H., 1955. Punch cards record runoff and soil~loss data. 
Agrie. Eng. 36: 664-666. 
19. Wischmeier , W. H. and D. D. Smith, 1958. Rainfall energy and its re[a~ 
tionship to soil loss . Trans. Arner. Geophysl. Union 39:285~291. 
• 9 
Effect of Ilope lenqtft on 
runoff and loll 1011 
The effect of slope length on runoff loss is nol well understood and 
is a debatable issue. Slope length, as defined in the universal soil-loss 
equation, is the distance from the point of origin of overland flow to either 
the point where the slope decreases [0 the extent that deposi tion begins 
or the point where runoff enters a well defibed channel drat may be part 
of a drainage network or a constructed channel such as a terrace or diver­
sion (Smith and Wi schmei er, 1957). 1herefore, the slope length factor (L) 
is the ratio of runoff/soil Joss from a particular slope length to that from 
a 72.6 foot length when all other condi tions are the same. 
Wischmeier (l%6) reported from his investigations on 21 locations 
that the effect of slope length on runoff per unit area was of questionable 
significance. He found that for 18 locations the total growing season run­
off per unit area was greatest on short slopes. Total dormant season run­
off was found to be greater on longer slopes for 11 locations, but it was 
equal to or greater than the runoff on the short slopes for the other 10. 
Borst and Woodburn (1942) also found no significant effect of slope length 
on water runoff. 
Numerous studies, however, have shown that the soil loss per unit 
area is related to slope I ength. The effect of slope length on soi I loss 
may be a result of increased erosive potential due to greater accumulation 
of runoff on longer slopes. Runoff velocity increases with an increase in 
runoff accumulation. Zingg (1949) reported that average soil loss per unit 
area increased in proportion to the 0.6 power of slope length. Musgrave 
(1947) found that exponent m, (A/72.6)ffi, was 0.35. Wischmeier (1972) has 
sho\\-n that the value of the m exponent varies from 0.3 to 0.7 with a median 
value of 0.45. 
Another complicating factor in defining the exact relationship between 
slope length and runoff and soil loss from field plot experiments is the 
nature of the slope. Runoff and soil loss are significantly influenced by 
whether tbe slope is convex, concave, complex or regular. Gard and Van 
Doren (1950) reported that on a 5% slope, 2l0-foot plots had less runoff 
and soil loss per unit area than plots 140 feet long. They reported that 
erosion on concave slopes was worse [han the soil-loss measurement 
implied. Lixandru (1968) reported from Rumania that soil and water losses 
72 Soil erosion problems on an a/fisol in Western Ni geria 
on 12% regular-slope plots increased with increase in length up to 35 
meters. Young and Mutchler (L969) concluded that soil loss from irregular 
sLopes depended on the steepness of a short section of th e slope imm edi­
ately above the point of measurement. They visualized that soil was pri­
marily transported by raindrop splash 10 a rill system and downward by 
runoff in the rills. A bleakdo'~n of the rill system at the bottom of concave 
slopes (due to decreasing local steepness) resulted in sheet flow and 
sediment deposition thereby decreasing th e soil toss from concave slopes. 
Nature of Slope on I1TA ' s Slope-Length Plots 
The slope-length plots at lITA are not of regular slope. There are 
two general slopes of 10% and 1S %: . On each of the slopes) plots of 12.5m 
and 3'). Sm were set up . The general nature of the slopes of these plots is 
shown in Fi g. 9.1. The longer plot on the 10% slope has an exact slope 
(II) 1~ SLOPE: PLOT 
(il con.e. slope of 37·5m plot 
Hi) re\lular slope of (2·5m plot 
[ b l 15% SLOPE PLOT 
[ i) c"'"ple. s lope of 3·' · 5m plot 
convex 
---~, 
c,on CQ'Je 
(ii) COnCO"9 Slope of 12. · 5m plot 
Fig.9.1 Slope characteristics and slope length of runoff -plots at 10 and 
15 percent slopes. 
Effect of slope length on runoff and soil loss 
of 9.3% and the slope is convex with curvature about 27m from the col­
lection system. The 12.5-m plot on the 10% slope has a regular 10% slope. 
The 37.5m plot on the 15% slope has a mean slope of 13.4%,but the slope 
is a complex with a convex OIrvature about 2J m and a concave cllrvature 
about 10 m from the collection system. The 12.5 m plot on the 15% slope 
has a mecm slope of 19.4% with a concave curvature about 10 m from the 
collection system. While such complexity could be considered an uw 
desirable complication it is by no means typical of the forest areas 
of West Africa. 
Th c interpretatioll of the rcsu I ts from these plots, therefore, mu st 
include ((msidcrat inn not only of degree and length of the slopes but also 
of the nature of the slopes. 
Efre cl oj Slope LOlgrh on Runoff rnd Soil foss Under ~aize-Cowpea 
Ro!afiofl for Irregular Slopes: 
The runoff and soil loss data for 1972 and 1973 arc shown in Tables 
9.1 and 9.2 respectively. Hegard!css of the slope, runoff loss per unit 
are.a \\C\s always less on the longer slopes than on the shorter slopes. 
The mean wata mnoff for 1972 was in the ratio of 1:1.76 for long and 
short slopes. Similar water nwon data for 1973 was ill the ratio of 1:2.42. 
TIle average soil loss during 1972 was similar to that of water runoff WIth 
a ratio of 1: 1. 77 for long and short slopes. In 1973, the soil loss data 
were in th e ratio of 1: 1.50. 
Table 9.1. Effect of contour length on runoff and soi I loss under maize­
cowpea rotation (a 1 First season 1972. Rainfa!!-
Run off/ lZ.5m long 37.5m long 
Soil loss 10.(J% 79.2% 9.3% 13.4% 
Runoff (rnm ) 230.2 214.3 133.6 125.8 
Soil loss 21.2 7.9 , 1.4 5.9 
(tons/ ha) 
Slope Regular Concave Convex Complex 
(b) Second season 1972. Rainfall -
Runoff/ 12.5m long 37.5m long 
Soil loss 10.0010 19.2% 9.3% 13.4% 
Runoff (mm) 18.8 21.7 9.1 7.7 
Soi I loss 2.7 3.2 1.4 1.1 
(tons/ ha) 
74 Soil erosion problems on an alfi sol in We stern Ni g eria 
The effect of the nature of the slope on water runoff and soil loss is 
obvious from !lIe data presented in Tables 9.1 and 9.2. Total soH loss 
during 1912 from the 12.:rm plot of regular 10% slope was 23.9 ton/ha 
compared to 12.8 ton/ha of soil loss from the 37.5 m plot of irregular 10% 
slope. During 1912, 2.15 times as much soil was lost from the 12.5 m plot 
of 10% regular slope as from the · 12.S m plot of 19.2% concave slope. 
During 1973. 54% more soil was lost from the regular slope than from th e 
steeper concave slope. 
Table 9.2. Effect of contour length on runoff and soil loss under rna i ze· 
cowpea rotation (a) First season 1973 Rainfall-
Runoffl 12·5m long 37.5m l ong 
$oilloss 10.0% 19.2% 9.]0,-6 13. 4% 
Runoff (mm) 193.1 203.0 88.5 80.5 
Soil loss 3i.3 22.8 21.5 15.8 
(tons/ hal 
(b) Second season 1973 . RainfaJl-
. I 
Runoff/ 12.5m long 37.5m long 
Soil loss 10. £JYo 19.2% 9. 3% r3.4% 
Runoff (mm) 88 .1 55.1 25.7 28.0 
Soi I loss 5.2 0.9 1.5 1,4 
(tons/ ha) 
Table 9.3. Effect 01 contour length on runoff and soil loss under bare 
fallow treatment. (8} First season 1974. 
Runoff 12.5m long 37.5m long 
Soil loss 70. 0% 19. 2% 9. 3% 13.4% 
Runoff (mm) 302.7 260.4 175.6 157.3 
Soil loss 77.3 34.6 114.3 68.6 
(tons/ ha I 
Slope Regular Concav e Convex Complex 
(b ) Second season 1974. 
Runoff 72.5 m f.ong 3 7.5m l ong 
Soil loss 10.0% 19. 29-0 9.3% 13.4?1: 
Runoff (mm) 162.4 140.7 52 .3 52.7 
Soil loss 32.3 14.0 40.2 26.8 
(tons / ha) 
Effect of slope length on runoff and soil loss 75 
Also during 1972,83% more soil was lost from the 37.5 m plot of 
9.3% con vex slope than from the 37.5 plots of 13.4% complex slope. 
Similar data for 1973 indicate that 34% more soil was lost from the convex 
slope than from the complex slope. 
It is justified to conclude, therefore, that the nature of slope \\as 
more important than the degree of slope within the slope ranges of the 
present investigations . Under maize-cowpea rotation, convex and regular 
slopes had higher runoff and soil losses than Concave slopes. 
effect of Slope Length on Runoff cmd Soil Loss Under Bare fallow Trent 
ments for Irregular Slopes: 
Data presented in Table 9.3 indicate the interaction between tIll' 
nature of slope, the degree of slope and slope length on runoff and soil 
loss. Once again, water runoff is greater on the shorter slopes than Oil 
the longer ones. The water runoff per lll1it area on the 12.5 m plots was 
twice that from the 37 .5 m plots. The soil loss on from the 37.5 m plots 
was 58% greater than that from 12.5 m plots. 
The effect of the nature of the slope on runoff can be seen by com­
paring water runoff per unit area from the 12.5 m plot of 10.0% regular 
slope with that of the 12.5 m plot of 19.2% concave slope. The water 
runoff from the 10% regular slope was 16% more than that from the 
19.2% concave slape. The soil loss however, was 2.25 times greater from 
the regular slope than from the concave slope of the same length and 
double the gradient. 
A similar comparison for 37.5 m plots indicates the effect of con vex 
versus complex slope on water runoff and soil loss. The 37.5 m plot of 
9.3% convex slope had 8.5% more water runoff and 62% more soil loss per 
unit area than the same length plot of 13.4% complex slope. 
CONCLUSIONS 
• Water runoff per unit area was always greater from shorter than from 
longer slopes. 
• Under maize-cowpea rotation, more soil and water loss per unit area 
was lost from convex and regular slopes than from complex or con­
cave slopes. The soil and water loss per unit area was also greater 
from shorter than from longer slopes. 
• Under bare fallow, although water runoff per unit area was higher 
from shorter than from longer slopes, soil loss generally in creased 
with increasing slope length. 
76 Soil erosion problems on analfisol in nestem Nigeria 
REFERENCES 
1. Borst,H. L. and R. Woodburn , 1942. The effect of mulching and me­
thods of cultivation on runoff and erosion from Muskingum silt 
loam. Agr. Eng. 23: 19-22. 
2. Card, L. E. and C. A. Van Doren , 1950. Soil losses as affected by 
cover,rainfall and slope. Soil Sci. Soc. Am er. Proc. 14-: 374-178. 
3. Jamison, V. C. and D. B. Peters, 1967. Slope length of daypan soil 
affects runoff. Water Resources Res . .J . 471-480. 
4. Lixandru , C.,1968 . Determination of critical slope length in . relation 
to erosion. Stiinta Sol. 6: 12-18 
S. Musgrave, G. W. ,1947. Quantitative evaluation of factors in water ero-
sion - a first apPlOximation. J. Soil and Water Conserv. 2: 
133-138. 
6. Smith,D. D. and W. H. Wischmeier, 1957. Factors affecting sheet and 
rill erosion. Amer. Geophys. Union Trans . 38 : 889-896 . 
7. '~ischmeie(, W. H. 1966. Relation of field-plot runoff to management 
and physical factors. Soil Sci. Soc. Amer. Proc. 30: 272-277. 
8. Wischmeier, W. H. , 1972. Upslope erosion analysis. Chapter 15 in 
H. W. Shen, ed. Environmental lmpact on Ri vers , Colorado Stat<:· 
University , Fort Collins. 
9. Wi schmeier, W. H., D. D. Smith and R. E. Ukland, 1958. EvaJuation of 
factors in the soil-loss equation . Agr. Eng. 39: 458-462. 
10. Young, R. A. and C. K. \1utchler, 1969. Soil mo\'ement on irregular 
slopes. Water Resources Res. 5: 1084-1089 . 
11. Zingg, A. W. 1940. Degree and length of land slope as it ufre cts 
soil loss in runoff. Agr. Eng. 21 : 59. 
• 10 
nutrIent 1011 fn water runoff 
Lack of response or relatively little response to applied fertilizer in 
tropical soils may be attributed to leaching losses and partially 
to losses in water runoff and eroded sediments. The eutrophication of 
waters in rivers and streams is also the direct result of these losses. 
Quantitative information of the magnitude of such losses fn)m West African 
soils is rather scanty, but there is little doubt that the removal of solutes 
and the Loss of applied fertilizer are important factors depleting soil 
fertility. Various workers have attempted to estimate the quantity of 
solutes lost from soils in temperate regions.Drum et al (1960) for example, 
reported a loss of 82 t/mi 2/yr of solutes from soils in the U.S . and 44.5 
t/mi 2/ y r from soils in the U.S. S. R. 
Losses of P in runoff water and eroded sediments in temperate regions 
have received the attention of various workers (Ryden et aI, 1973). Duley 
(1926) reported that the major loss of P in runoff water was through eroded 
sediments. These results were reported from Georgia where P losses of 
only 0.03 to 0.04 kg/hajyr were found in the runoff water. Engelbrecht 
and Morgan (196l) found P losses ranging from 0 to 16 kg/ha/yr in surface 
drainage water in Illinois. Munn et a1 (1973) reported that simulated runoff 
tests conducted on micro'plots of some Obio soils showed a significant 
correlation between total phosphorus in runoff and the amount of soil 
removed by erosion. From watershed investigations, Schuman et al (1973) 
reported a loss of 0.5 to 2.1 kg/ha of P in water runoff. 
Although the liteIatUIe indicates that most of the P losses ocrur 
through eroded sediments , the concentration of P in runoff water has been 
reported high enough to be a primary cause of eutrophication of water 
supplies. 
Th ere have been many reports concerning the loss of nitrogen and 
other nutrient elements in runoff water. Rogers (1944) reported that eroded 
sediments from com land were richer in Nand P than the original soil. 
Bryant and Slater (1948) found from their studies in Iowa that although 
only small amounts of soluble material were lost in runoff water, the 
removal of solutes and the loss of applied fertilizers were important 
factors in soil fertili ty depletion. Mattyasovszky and Duck (1954) reported 
that runoff water from a heavy stonn carried 9.8 ppm of ~03-N and 3.2 gi l 
78 Soi 1 erosion problems on an allisol in West ern Nigeria 
of sediment. Moe et al (1967) found Jess than 2 kg/ ha of urea~N in runoff 
water. Total loss ofN in this study ranged from 2.4 to 12.)% of applied N. 
In other investigations,thesc authors reported that the maximum loss of N 
in runoff water from a 12. 5~cm stonn amounted to 15% of the applied ferti~ 
1izer. Frere (1971) found considerable variation in the nutrient con tents of 
runoff from different watersheds. When a major storm was composed of 
more than one peak, (he average nutrient concentration varied by as much 
as 200 percent between waterflow peaks. Barnett et al (1972) reported 
from their studies on some Puerto Rican soils that the average concentra~ 
tion of N in runoff water ranged from 0.01 to 0.02 ppm and the average 
concentration of K varied from 0.01 to 2.29 ppm. Nutrient losses in runoff 
water in northern Nigeria have been reported by Kowal(19J2). The average 
annual loss of Ca , \ig, and ~a in runoff water and eroded soil varied from 
14 to 30 kg/ha. The average annual N loss ranged from 7 to 19 kg/ha. 
Methods of Sample Collection and Water Analyses: 
In the studies reported here runoffwater samples from each of 24 plots 
were collected after every storm during 1972 and 19'13 and were either 
analyzed immediately or stored at 4°C pending anlysis. The water samples 
were analyzed for pH, conductivity, ~03~N, P04~P, K, Ga and Mg. The 
concentration of Ca and K were determined by flame photometry and the 
concentration of Mg by atomic absorption spectrophotometry. Phosphorus 
was measured colorimetrically using the molybdic acid~blue melhod; 
NO ~~ was measured colorimetrically using brucine (Greweling andPeach, 
1965). 
NUTRIENT CONTENTS 
(A) Effect of Cropping Sequence attd Soil4anagemettt : 1972-73 Results : 
The pH of th e runoff water was significantly affected by soil and 
crop management treatments . For instance during April 1973, the pH of 
runoff water from bare~fallow plots was 6.6 and the pH of runoff water 
from mulched and no~tillage plots was 7.1. By October 1973, the pH of 
runoff water from bare~fallow plots was 5.9; from cowpea-maize (con~ 
ventional plowing) plots, 6.4 ; from maize~maize (conventional plowing) 
plots, 6.5; frommaize~cowpea (no~tillage) plots, 6.6; and from maize~ 
maize (mulched) plots, 6.7. 
Total Nutrient Loss: 
Total nutrient losses in the runoff water were proportional to the 
surface runoff and were, therefore, affected both by slope and soil-man~ 
agement treatments (Figures lO.l and 10.2) The nutrient losses from the 
no~tillage plots during 19]2 must be viewed separately because the soil 
surface had been disturbed and there was no surface mulch. For the sake 
of comparison among treatments, therefore, the results of the 1973 studies 
are di scussed here. 
Nutrient loss in water runoff 79 
1972 
50 __ tKlre fallow 
D---<J maize-moire (plowed) 
J>..--...L>. cowpea-molze (plowtd) 
___ malze-cowpea(no tllkIc.I~) 
46 
m alII-moire (mijlch) 
44 
42 
40 
:: ~4 
o 
~ 32 
~ 30 
c 
~ 28 
26 
••  
" 24 
c 22 
• 
~ 
:> 20 
'" 
18 
J! 
.2 \6 
14 
12 
10 
8 
6 
4 
2 
o~~~~-:--~~~~----~~~~~--~~~ 
2 3 4 5 6 7 8 9 10 II 12 13 14 15 16 17 
.10 p. "I. 
Fig. 10.1 Effects of slopes, crop rotations and residue management on 
loss of total nutrient elements in runoff water in 1972. 
Total nutrient losses in runoff water followed the order of bare~ 
fallow> maize·maize (conventional plowing» cowpea-maize (conventional 
plowing) maize-cowpea (no·tiUage» maize-maize (mulched). Total annual 
nutrient losses from the bale-fallow plots ranged from ")4 to &4 kgjha. 
80 Soil erosion problems on an allisol in Western Nigeria 
1973 
100 
_ - bare fo lio" 
q6 o----tl moize-rnGlze (plowed) 
"-----6 COtIIpeo- molze (plowed) 
92 
-- rnaiza-cOOfpea (no IIIlaQe l 
BB molz.- molJ. (mulal. d) 
B4 
B,O 
76 
72 
-;: 68 
"0- 
~ 64 
"c-o 
~- - 60 
0 
c ~~ 
=> 
~2 
!- 
<> 
~ 4B 
.-!O 
44 
• 
£ 40 
~ 
~ 36 
; 
c: 32 
~ 
0 28 
24 
2 
16 
12 
8 
4 
2 3 4 !\ 6 1 8 9 10 II 12 13 14 I:) 16 rr 18 
.'ope % 
Fig. 10.2 Effects of slopes, crop rotations and residue management on 
loss of total nutrient elements in runoff water in 1973. 
Total annual nutrient losses from the maize'rnaize (conventional plowing) 
plots varied from 10 to 32 kg/ha and those from the cowpea'maize (con' 
ventional plowing) from 5 to 23 kg,lha. The total annual Dutri ent losses from 
the mulched and no,tillage plots were the lowest and ranged from 0 to 5 
kg/ba from the mulched plots and 2 to 7 kg/ha from the Do-tillage plots. 
Nutrient loss in water runoff 81 
Loss of Different Plant Nutrients: 
The effects of soil and crop management treatments on losses o f 
various plant nutrients in runoff water for both growing seasons of 1972 
and 1973 are shown in Tables 10.1, 10.2, 10.3 and lOA. Only the results 
of the 1973 studies are discussed here. 
There were no definite trends in nutrient losses with regard to slope 
steepness. The highest nutrient loss occurred from the bare-fallow plOlS 
and the lowest from the mulched and no-tillage plots . The losses of N03-N 
in the runoff water from the S% slope plOlS during the first season 1973 
were 3.3 kg/ ha from the bare-fallow plot , 1.5 kg/ ha from the maizc-mai::e 
(conventional plowing) plot , 0.1 kg/h a from the no-tillage plOl and 0 .04 
kgjha from the mulched plot. The losses of P were less , ranging from 0 to 
1. j kg/ ha from 5% slope plots. The losses 0 f K ranged from 0.1 to 9 kg/ ha, 
those of Ca from 0.1 to 19 kg/ ha and those of Mg from 0 to 3.3 kg/ ha . 
Similar losses were recorded during the second season. 
Effccl of Length of Slope 011 Nutriel1t Loss il1 Water Runoff: 
The effect of length of slope on nutrient loss during the first and 
second seasons of 1972 and 1973 are shown in Tables 10 .5 and 10.6. 
Nutrient losses in water we re proportional to the quantity of runoff amI, 
therefore, the analysis presented in Chapter 9 applies here. During 1972 
losses of NO -N varied from 0.09 to 6.0 kg/ ba, those of P from 0 .06 to 
1.9 kg/ ha, those of K from 0.5 to 13.4 kg/ ha , those of Cafrom 0. 3 to 14.1 
kg/ ha, and those of Mg from 0.3 to 4.2 kg/ ha. 
Nutrient Losses in Runoff Water at Different Stages of Crop Growth : 
The losses of NO -N in runoff water at different stages of crop growth 
are shown in Figure 10.3. As expected, the losses were the highest from 
the bare-fallow plots and lowest from the mulched and no-tillage plots. 
The relative loss of nitrogen from the 5- 10- and 15- percent slope plots 
increased wi th time from the onset of the rainy season in April to the end 
of first cropping season in August. 
The change in the hydro-thennal regime of the soil from hot and dry 
at the beginning of the season to cool and moist toward the end may be 
one of the reasons for higher nitrate losses in runoff water during August. 
Similar data on P, K, Ca and Mg losses from the 5 percent slope plots 
are shown in Figure 10.4. While the losses of NOrN increased during the 
growing season, P , K, Ca and Mg losses were highest during mid-season 
and decreased markedly toward the end. 
00 
N 
Table 10.1. r--'utrient loss ill rUlioff water (kg/ ha) for different slopes and soil management treatment s. (First season 1972) 
1% 5% 10% 15% 
Rotation N0 ,N P0 ,P K Ca Mg NOS ,N P0 'P K Ca Mg NOS,N P0 ,P K Ca My 
3 4 4 NOS ,N P0 ,p K 
4 Ca Mg 
4 
Bare 3.85 0.41 4.540 8.07 1.80 6.25 0.63 7.50 i4.60 2.69 7.34 1.81 8.3015.674.78 5.25 0.54 6.17 14.87 4.77 
Maize 0.C02 0.001 0.006 0.04 0.006 1.11 0,03 0.51 2.19 0.09 0.24 0.14 0.23 0.580.12 0.29 0.02 0.34 0.78 0.13 
(mulch) 
Maize 2.42 0.14 1.48 4.66 0.60 1.99 0.39 3.81 5.84 2.05 1. 92 0.14 1.863.230.59 2.09 0.17 2.29 2.05 1.71 
Maize 0.42 0 ..3 4 0.39 0.87 0.45 1.83 0.41 5.58 11.26 2.00 2.73 0.35 3.58 4.41 2.30 3.06 0.34 4.40 12.86 3.65· 
(no·ti Ilage) 
Cowpea 0.15 0.014 0.24 0.28 0.58 0.80 0.17 3.04 3.65 0.76 0.63 0.09 1.t3S 2.91 0.24 0.74 0.00 2.10 1.79 0.46 
(plowed) 
Table 10.2 . Nutriellt loss in runoff water (kg/ ha) as affected by different slopes and soil management treatments. (Second season 1972 : 
1% 5% 10% 15% 
Rotation N0 ,N P0 ,P K Ca Mg N0 ·N P0 ·P K Ca My NO .N PO .p K Ca My N0 ·N P0 ·P K Ca Mg 
3 4 3 4 3 4 3 4
Bare 0.48 0 .26 0.62 4,95 0.41 0.68 0.21 1.18 7.59 0.40 0.28 0.16 0.61 4.28 0.37 0.80 0.53 0.83 5.89 0.49 
Maize 0.00 0.00 0.00 0.00 0.00 0.02 0.004 0.03 0.25 0.02 0.06 0.02 0.13 0.72 0.07 0.05 0,02 0.10 0.57 0.04 
(mulch) 
Maize 0.04 0.02 0.08 1.69 0.01 0.19 0.03 0.25 2.14 0.18 0.10 0.07 0.20 1.68 0.13 0.18 0.10 0.29 1.63 0.14 
CO\l\lpea 0.03 0.03 0.04 0.29 0.02 0.08 0.02 0.12 0.74 0.06 0.10 0.04 0.29 1.03 0.09 0.07 0.04 0.21 0.98 0.08 
(no,tillage) 
Maize 0.02 0.05 0.13 0.9) 0.09 0.53 0.09 0.46 3.39 0.32 0.13 0.03 0.22 0.73 0.10 0.44 0.29 063 3.31 0.28 
Taulp.l(l.~. Nutrient loss in run-off water (kg/ ha) as affected by different slopes ilnd soil management treatments 
(First Season 1973) 
1% 5% 1CIX. 15% 
Rotation N0 -N p~ -p K Ca Mg N0 ·N 
3 P04'P K Ca Mg NCl.J.N P0 .p K Ca My 
3 4 N0 ·N P0 .p K Ca My 
3 4 
Bare 3.B6 1.73 7.35 11.88 3.12 3.29 1.49 9.12 19.07 3.29 3.74 1.54 8.28 21.88 4.24 4.25 1.97 10.36 21.53 6.54 
Maize (Mulch) 0.00 0.00 0.00 0.00 0.00 0.04 0.01 0.12 0.140.03 0.14 0.07 0.62 0.30 0.11 0.16 0.80 0.44 0.22 0.10 
Maize 0.54 O.4B 2.01 3.31 0.74 1.52 1.18 8.00 11.21 2.54 0.43 0.36 2.21 3.91 0.91 O.SO 0.86 4.86 ~.01 1.76 
Maize INo·tillage\ o.n 0.04 0.21 o.n 0.06 0.\3 0.10 0.56 0.530.24 0.11 om 0.45 0.30 0.12 o.n 0.89 0.!l9 0.25 f).~1 
Cowpea (Plowed) 0.15 0.27 0.74 1.35 0.29 0.76 0.34 5.23 6.42 1.21 0.35 0.40 1.93 2.55 0.65 0.32 0.44 2.32 1.70 0.76 
TaUle 10.4. Nutrient loss in run-off water {kg/ hal as affected by stope and soil management treatment 
(Second Season 1973) 
1% 5% 1fYJ6 15% 
Rotation 
N03 ·N P04 ·p K Ca Mg N03 ·N P0 -p 
4 K Ca Mg N03 -N 
 P04-P K Ca Mg NOyN P0 .p 
4 K Ca Mg 
8are 11.37 1.88 Q.62 18.21 5.20 7.54 1.92 B.31 17.54 3.48 7.75 2.18 9.92 12.06 2.75 8.94 2.71 9.03 15.BO 2.77 
Maize Maize (Mulch) 0.00 0.00 0.00 0.00 0.00 0.22 0.02 0.20 0.22 0.05 0.44 0.93 0.74 0.47 0.15 0.51 0.13 1.60 0.77 0.23 
Maize 0.50 0.10 0.80 0.92 0.15 1.60 0.31 3.52 2.01 0.39 1.12 0.26 2.09 1.88 0.38 2.09 0.84 5.37 3.89 0.96 
Cowpea (No··till age) 0.30 0.03 0.25 0.41 0.19 0.32 0.07 1.31 0.47 0.14 0.48 0.13 2.03 0.80 0.18 0 .51 0.12 2.82 0 .75 0.30 
Maize (Plo""ed) 0.48 0.17 0.72 0.{\8 0.24 1.79 0.41 3.76 2.54 0.75 0.94 0.35 3.39 2.47 0.65 2.32 1.23 5.10 6.06 1.21 
CO 
IoN 
84 Soil erosion problems on an alfisol in West ern Nigeria 
Table 10.5. Contour length and nutrien t loss (kg/ha) in run-off {a\ First season 1972 
Slope 12.5mlong 37.5m long 
% N~-N PO"p K G Mg N03"N P04 -P K G My 
10.0 6.00 0.60 6.46 8.48 2.70 
19,2 3.51 0.70 5.77 18.89 2.65 
9 .3 1.65 0.44 3.42 13.77 U8 
13.4 2.01 0.29 5.84 11.75 5.06 
{bf Second season 1972 
10.0 0.08 0.08 0.52 3.93 0.32 
19.2 0.52 0.13 047 4.63 0.45 
9.3 0.09 0.06 0 .26 1.91 0_17 
13.4 0.15 0.07 0.27 1.89 0.21 
Table 10.6. Contour length and nutrient loss in \NEIer kg/ha. fa} First season 1973 
Slape 12.5m long 37.5m long 
% N03 ·N P04'P K G Mg N03·N P04'P K G My 
10.0 2.69 1.87 11.06 14.11 3.05 
19.2 2.19 1.75 10.60 13.72 4.24 
9.3 0.87 0.87 4.37 6.54 1.64 
13.4 0.57 0.60 3.78 618 1.55 
(b) Second season 1973 
10.0 2.51 0.91 13.40 6.91 1.42 
19.2 1.23 0.41 6.72 2.97 0.'76 
9.3 0.68 0.25 3_27 1.79 0.28 
13.4 0 .80 0.22 2.98 1.28 0.33 
Relative Nutrient Concentration in Runoff Water: 
Relative nutrient concentrations in runoff water on October 22, 1973 
are shown in Figure 10.5. The concentration of NOJ-N in runoff water was 
only slightly affected by 'soil, slope and crop-management treatmen ts_ 
Nitrate concentration ranged from 4 to 6 ppm. Concentrations of PO",-P, 
K, Ca and Mg, however, were significantly influenced by different treat­
ments_ The phosphate concentration was the high est in the runoff water 
from the cowpea plots in the maize-cowpea rotation with both no-tillage 
and conventional plowing treatments. Th e Ca concentration was signifi­
cantly higher in the runoff water from the bare-fallow plots than in the 
11"1 I · 1'1'. 15'1'. 
2 '01 
CIO 
Ie 5 .. SIo!>o 
1·61 
1, 2,3.4.5 
1·4 .. lie. ... 
j\, ~ ·3 1·2 
\ 
\ 
~ ·1 --~~ J! 
g ~ ---..... 
z I IIg 
'", -' 
il 5% 10% 
·'8I  t · 5 
·7 J 4 ·01 
• • 1 
· ~I 3 ·0' 
·4 
·3 2· 
· 2 ..., 
· 1 /~ 1·0 
L 1 
Aow. May Jun. "'1 . AII90 Aow. May Jill. JUI. AlIt. l , , >.------, b -,-~~l 
A.... M., ...... ~.I . A. ... Apr. 1I0y ....... JuL .... .. 
r iME 
Fig. 10.3 Loss of N03-N in runoff water at different 5tages 
of crop growth as influenced by soil rranagement Fig.10.4 Loss of nutrient elements such as P, K, Ca and Mg 
and crop rotation treatrrents. in water runoff at different stages of crop growth. 
86 Soil erosion problems on an alfisol in Western Nigeria 
OCT 22,1913 
8 N03-N 
r:: 
~~ : ~ 
4 ::!: 
- , '! ~ 
I: .. :. ~ 
O~~~'· ~·~----~~-
4 p 
2 
E O~~n3d-__~ ~.cL-__ LL~~L--L~~~ __ 
Q. §Maize-Cowpeas( No-Tillage) 
~ 120 • Maize - Maize (Mulc.hed) K 
r.f) 
z 
o 
!;i 60 
a:: 
t-
z 
W 
u 
z 
8 o Cowpt'as - Maize 
40 Ca 
~ Cowpt'as 
20 
o~~~~~----~~~~----~~~~~~~~~~---
4. 
2 
SLOPE (0'.) 
Fig. 10.5 Relative nutrient concentration in runoff water from different 
treatments of soil management and crop rotation. 
runoff water from the other treabnents. Similarly, the Mg concenttation 
was highest in the runoff water from the bare-fallow and cowpea plots 
under both conventional and no-tillage treatments. 
The concentrations of N03~N and P04-P recorded in runoff water is 
definitely high enough to enrich stream water. Concentrations of P above 
0.05 ppm are considered high enough to' cause. eutIoph icalion. The high 
concentrations of P in the runoff water from the no-tillage plots may be 
due to surface application of the fertilizer and the high solubility of super­
phosphate in the partially decomposed mulched layer (Fink and Wesley, 
1974). The high concentrations of K in the runoff water from the no-tillage 
Nutrient loss in water runoff 87 
SEPT. 14, 1973 
N 
6 
• Surface Ru noff P 
o Sub SUrface Water 
~o 
o 
~1 
IX: 
~ 
Z 
W 
<..J 
Z 
o 
u 
r-
16 Mg 
.-
8 .- r-
o -"" 
5 - 10 15 
SLOPE (%) 
Fig. 10.6 Relative nutrient concentration in surface runoff ana su~surface 
inter-flow water. 
plots may also be due to surface application of potash as well as th e 
release of K from the decomposing crop residue. 
The high concentrations of Ca and Mg in the runoff water from th e 
bare,fallow plots may be attributed to exposure of subsoil ri ch in Ca and 
Mg when the surface soil was removed by erosion. 
Relative Nutri ent COl1c el1 Irati ons il1 Seepage Waf er: 
During heavy storms in July and September of 1972 and 1973. in ter~ 
flow water was al so collected hom some plots on th e IS-perc ent s lope. 
The relative nutrient concentrations of th e interflow and surfacc cunof[ 
water from on e of th ese plots are shown in Figure 10.6. Th e NOrN con-
88 Soil erosion problems on an alfisol in Western Nigeria 
centralion in the interflow water was consistently 2 and 3 times higher 
than that in the surface runoff water and the Ca and Mg concentrations 
were also much higher. The PO -P concentrations in the interflow water 
were negligible compared to those in the surface runoff water. The con­
centrations of K is variable, but the K concentrations in the surface runoff 
water from the no-tillage plots were higher than those in the interflow 
water. 
1t appears that Jeaching losses of nitrogen may be significantly 
higher in tropical soj]s than the losses in runoff water. Although the total 
annual losses of N03-N in runoH water under crops may be only 2 to 3 
kg/ha, leaching losses may account for the relatively low efficiency of 
nitrogenous fertilizers in tropical soils. Because the phosphate concen­
tration in interflow water is negligible, the pollution of rivers and streams 
in tropical soils can be minimized by soil management practices, e.g. 
mulching and no-tillage techniques that minimize runoff and favor inter­
flow. 
Changes in Nutrient Concentrations with Time after Application: 
Changes in the concentrations of N03-N, P04-P and K in the runoff 
water from the bare-fallow and conventionally plowed maize plots with 
time after fertiliZer application are shown in Figure 10.7. The concentra­
tion of N03·N in the runoff water increased a few days after fertilizer 
application and decreased sharply 20 to 2S days after. No. consistent 
pattern in the nitrate concentration was observed thereafter. The frequency 
of rains significantly influenced nitrate concentration. The concentration 
of NOrN in the runoff water was substantially increased by rain after a 
prolonged dry spell. The P04-P concentration in runoff water was highest 
7 to 10 days after application of single superphosphate, and reached a 
constant level about 20 days after application. The phosphate Concentra­
tion reached a steady value of 0.1 ppm 90 days after. The K concentration, 
however,was highest immediately after application and decreased steadily 
with time after application. The K concentIation decreased from about lO 
ppm immediately after application to 3 ppm 50 days after and leveled off 
at 2 ppm between 6S to 90 days. 
Relation betwe en Vo 11-1111 e of Run" ff and Nurri enl Concentration : 
From the data of five consecutive rainstonns between May 28 and 
June 2, 1972, the runoff losses from bare-fallow plots ranged from 0.22 to 
30.19 mm, while those from conventionally plowed maize plots varied from 
0.09 to 11.23 mm. The concentrations of N, P and K in the runoff water 
were relatively independent of runoff volume. During one slOrm the con­
centration of NOyN was 3 ppm in 0.18 mm of runo£( and 3.7 ppm in 1.8 
mm of runoff. The P concentration during this period was stead)' at 0.35 
9"Q\\\ a.M \\\at 0\ ¥. a\ ') \1;) ~ \'l\\\\\. 
NulT; ent loss in water tunotf 89 
8 
7 -:>----------e Bores N 
x-- xMoize 
6 
4 
3 
2 
p 
~ 1-4 
e 
~12 
~I 
~ 
Q: o-a 
zt- 
~06 
z 
80-4 :;> )I. 
0 x x ~ 6 
x 
x x 0 (') 
0-2 y. 
x 0 ~ x 
0 0 0 
5 10 15 20 25 30 35 -40 45 50 55 60 65 70 
16 K 
x 
s 
0 
4 ~ x 0 0 
x )( 
2 0 
It 0 6 
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 
Do)'S After Ap plication 
Fig. 10.7 Changes in the concentration of N03-N. P and K at different 
times after fertilizer application. 
(B) NutrieNt Lo sses i~ Runoff Water as Arrec led by Different Mulch Rates : 
Total Nutri ent loss : 
The effects of different mulch rate s and s lopes on total nutrient 
losses in water runoff from uncropped plots are shown in Figure 10.8. 
Total nutri ent losses decreased logarithmically with increases in mulch 
late. FOT example , the mean annual nutri ent losses were 54.6 , 9.5, 4.2 
90 Soil erosion problems on an alii sol in Western Nigeri a 
,!Xl 
o 
'Ill 
c 
2 I 
0----0 ~ ,00001'I"ICI 
......---. 4 lon .. nl(l 
...---.-. Ei ,o",/tla 
_ ___ r.G-" 
4 6 • 9 .0 It 12 13 14 ~ 
alope % 
Fig. 10.8 The effects of different mulch rates and slopes on total nutrient 
losses in runoff water. 
and 1.9 kg/ha from plots mulched with 0, 2, 4 and 6 tons of straw per 
hectare. The average annual nutrient loss from the no·tillage plots was 
3.6 kg/ha , about the same as that from the plots mulChed with 4 tons of 
straw per hectare. 
Lo sse s of Different Plan t Nu trietlts : 
The losses of different plant nutrients as affected by mulch rcUe and 
slope steepness during the first and second seasons of 1974 are shown in 
Tables 10.7 and 10.8. There were no significant effects of slope steep· 
ness on nutrient losses. The highest losses during one season were 13.4 
kg/ha of NO ·N, 2.5 kg/ha of PO .p , 20 kg/ha of K, 14 kg/ha of Ca and 
2.7 kg/ha of Mg. Negligible nutrient Josses were recorded from the plots 
mulched with 4 to 6 tons of straw per-hectare. 
Table 10.7 . Nutrient loss in run-off ""ater (kg/hal at different mulch rates (tons/hal. 
\ Fi rst Season .'1314\ 
Slopl3 0 2 4 6 No (if/age 
% 
N~-N P04 -P K Ca My N~ -N P04 -P K Ca My N03 ·N P04 -P K Ca My N03 -N P04 -P K Ca Mg No..;.N P04 -P K Ca Mg 
1 9.47 2.16 )2,40 11.591.78 0.14 0,03 0,16 0.17 0,04 0,09 0.03 0.11 0.13 0.10 0,00 0.00 0.00 0.00 0.00 0.15 0.04 0.16 0.17 0.06 
5 10.16 2.50 19.90 14.082.66 1.59 0.35 1.90 1.52 0.71 0,24 0.14 0.51 0.33 0.10 0.19 0.03 0.19 0.17 0.D7 0.29 0.07 0.32 0.28 0.10 
10 7.35 1.45 11.22 8.71 2.09 1.04 0.29 2.03 1.17 0.36 0.46 0.15 0.13 0.70 0.29 0.23 0.07 0.61 0.37 0.11 0.36 0.15 0.88 1.49 0.18 
15 13.43 2.43 15.04 9.21 2,60 1.00 0.39 2.06 0.72 0.36 0.61 0.12 0.13 0.69 0.18 0.33 0.10 0.68 0.42 0.18 0.34 0.11 1.78 0.55 0.26 
Table 10.8, Nutrient loss in run-off water (kg/ ha) at different mulch rates (tons of straw/ hal 
(Second Season 1974) 
Slope 0 2 4 6 No tillage 
% 
NO -N PO·p K Ca My N0 N P0 'P K Ca Mg N0 ·N PO -P K Ca My N0 -N PO -P K Ca Mg N0 ·N P0 ·P K Ca My 
3 4 3 4 3 4 3 4 3 4
1 3.48 1.17 3.75 9.09 0.58 0.58 0.26 0.53 0.14 0.13 9.96 0.02 0.04 0.00 0.02 0.00 0.00 0.00 0.00 0.00 0.16 0.03 0.15 0.22 0.04 
5 1.48 1.17 3.75 19.87 0.64 1.49 0,67 0.58 3.96 0.57 0.43 0.20 0.71 1.04 0.13 0.10 0.03 0.12 0.13 0.03 0.16 0.03 0.22 0.29 0.05 
10 1.11 0.71 2.64 5.61 0.31 0.49 0.33 1.28 2.25 0.22 0.40 0.12 0.72 1.40 0.31 0.24 0.06 0.33 0.35 0.06 0.24 0.06 0.45 0.58 0.09 
15 1.71 0.72 2.68 4.98 0.52 0.83 0.37 0.14 4.71 0.57 0.63 0.30 1.52 2.33 0.30 0.29 0.07 0.45 0.67 0.11 0.31 0.10 0.69 0.65 0.14 
-I.e:> 
92 Soil erosion problems on an alfisol in Western Nigeria 
Table 10.9. Effect of slope length on nutrient loss in ~ater run-off under 
bare fa II ow. (F i rst Sea son, 19741 
12.5 m long 37.5 m long 
Nutrient Run -off Run- off 
kgl ha 10.(J% 19.2% 9.3% 73.4% 
N03-N 7.6 10.5 3.4 4.5 
P 2.6 1.9 1.6 1.5 
K 17.3 14.5 7.7 7.n 
Ca 5.8 11.2 4.2 4.3 
Mg 2.3 4.2 2.2 1.6 
Table 10.10. Effect of slope leng1h on nutrient loss in water run-off und er 
bare fallow. (Second Season, 19741 
12.5 m long 37.5 m long 
Nutdent Run-off Run-off 
kg/ ha 1OJJ% 19.2% 9.3% 13.4% 
N03 -N 4.2 3.1 3.9 3.8 
p 1 .7 2.0 2.1 2.1 
K 1.3 1.2 1.4 1.2 
Ca 2.6 3.7 2.4 2.6 
Mg 0.6 0.6 0.5 0.6 
The effects of slope length on nutrient losses in runoff water are 
shown in Tables 10.9 and 10.10. Nutrient losses in runoff water from plots 
mulched at the rate of 4 to 6 tons of suaw/ha or from the no-tmage plots 
were relati vely negligible. 
CONCLUSIONS 
Although th e total losses of NO -N, Po .p and K in runoff water are 
rather small, the relative concentration of these elements is high enough 
to enrich water and cause pollution of streams and lakes. The leaching 
losses of nitrogen, as indicated by higher concentrations of No -N in 
inter-flow water further strengthens the case for llsing minimum tillage 
and mulch farming techniques to conserve soil and water and minimize 
pollution hazards in the trop.ies. 
Nutrient losses in runoff wa.ter from plots mulched at the rate of 4 to 
6 tonsjha of straw or flOm the no-tillage plots were negligible. 
Nutri ent loss in uater runoff 93 
REFERENCES 
1. Barnett, A.P.,] .R. Carreker and F. A bruna, 1972. Soil and nutrient 
losses in run,off wi th selected cropping treatments in tropi cal 
soils. Agron. J. 64: 391-395. 
2. Black, C.A., 1970. Behavior of soil and fertilizer phosphorus in 
relation to water pollution: Agricultural practices and water 
quality. Pages 72 - 93 in The Role of Agriculture In Clean Water. 
Ames, Iowa. Nov. 18-20, 19]0. 
3. Bryant,]. C. and C. S. Slater, 1948. Runoff water as an agent in the 
loss of soluble materials from certain soils. Iowa St. CoI1. J. 
Sci. 22: 269-297. 
4. Drum,W. H., S. G. Heidel and L. J. Tison, 1960. WOJld wide run'Off of 
dissolved solids. lnt. Ass. Sci. Hydro1. Pub!. 51. Gen. Assembly 
Helsinki: 618-628. 
5. Duley, F. L. , 1926. The loss of soluble sal ts in runoff water. Soil Sci. 
21: 401-409. 
6. Englebrecht, D. S. and J.]. Morgan, 1961. Land drainage as a source 
of phosphorus in Illinois surface waters. P. 74-79. Sec. Tr. 
W61-3. U. S. Public Health Service, Washington, D. C. 
7. Fink, R.]., and D. Wesley, 1974. Com yield as affected by fertiliza­
tion and tillage systems. Agron. J. 69: 70-JI. 
8. Frere, M.H., 1971. RequiSite sampling frequency for measuring nutrient 
and pesticide movement with runoff water. ]. Agric. and. Food 
Chern. 19 (5): 837-839. 
9. Grewcling, T. and M. Peech; 1965. Chemical soil tests. Cornell Univ. 
Agric. Expt. Station Bui. 960. 
10. Johnston, W. R. , F. Ittihadish, R. M. Daum and A. F . Pillsbury, 1965. 
Nitrogen and Phosphorus in tile drain effluent. Soil Sci. Soc. 
Amer. Proc. 29: 28/-287. 
11. Kowal,]., 1972. The hydrology of a small catchment Basin of Samaru, 
Nigeria IV. Assessment of soil erosion under varied land maw 
agement and vegetation cover. Niger Agric. ]. 7: 134-147 . 
12. Mattyasovszky, ]. and T. Duck, 1954. The effect of erosion on the 
nutrient status of soils. Agrokem Talajt 3: 163-172. 
94 Soil erosion problems on an alfisol in Western Nigeria 
13. Moe, P. G., J. V. Mannering and C. B. Johnson, 1967. further studies 
of nillogen losses in surface runoff water on fragipan soil. Res. 
Prog. Rep. Purdue Univ. Agric. Exp. Sta. No. 287. 
14. Moe, P.G., J. V. Mannering and C.B. Johnson, 1967. Loss of fertilizer 
N in surface runoff water. Soil Sci. 104: 389-394. 
15. Moe, P.G., J. V. Mannering and C. B. Johnson, 1968. A comparison of 
nitrogen losses from urea and ammO'niun nitrate in surface runoff 
water. Soil Sci. lOS: 428-433. 
16. Munn, O. A. , E. O. Mclean, A. Ramiroz and T.J. Logan, 1973. Effect 
of soil, cover, slope and rainfall factors on soil and phosphorus 
movement under simulated rainfall conditions. Soil Sci. Soc. 
Amer. Proc. 37: 428-431. 
17. Rogers, H. T. 1944. Plant nutrient losses from a COlD, wheat, clover 
rotation on Dunmore silt loams. Soil Sci. Soc. Amer. Proc.6:263-
271. 
18. Ryden, J. C., J.K. Syers and R. F. Harris, 1973. Phosphorus in runoff 
and stream. Adv. Agron. 1973: 1-45. 
L9. Schuman, G. E., R. G. Sponier and R. F. Piest, 1973. Phosphorus 
losses from four agri cultural watersheds on Missouri Valley 
Losses. J. Soil Water Conserv. 22: 228-231. 
20. Timmons, D. R., R. E. Burwell and R. F. Holt, 1968. Loss of crop 
nutrients through runoff. Minnesota Sci. 24: 16-18. 
• I I 
nutrient 1011 in eroded 
ledimentl 
Tolerable limits of soil erosion depend on the depth of the surface 
soil, the nutrient status and physical chruacteristics of the subsoil and 
the nature of the crops to be grown. Soil erosion results both in loss of 
nutrients and degradation of soil physical characteristics. In this chapter, 
the loss of nutrients with eroded sediments will be discussed. 
Massey et al (1973) reported an average loss of 192 kg of organic 
matter, 10.6 kg of N and 1.8 kg of exchangeable K per hectare on a Wis~ 
roDsin soil of 11 percent slope. Osborn and Mathews (1955) found that 
losses of N from the 0-15 on layer of soil ranged from 4S percent under 
continuous small grains to 60 percent under continuous row cropping. 
Thomas et al (1968) reported that the highest concentrations of nutrients 
in the soil lost from various treatments were 633 ppm of Ca and 104 ppm 
of K. The total loss of Ca was 1622 kg/ha while that of K ranged from 
0.14 to 0.22 kgJha. One major nutrient lost in the eroded sediment is 
applied phosphorus (Ensminger, 1952; Gupta and Singh, 1967; Scarsetb 
and Chandler, 1938; Yolk, 1945). Extensive loss of nitrogen in eroded 
sediments has also been reported by various wolkers (Kowal, 1972; 
Massey et ai, 1953; Osborn and Mathews, 1955; Rogers, 1944). 
Methods of Nutrient Analysis: 
For the studies reported here composite samples of e~oded sediments 
from all stonns were collected from all 25 plots at the end of each growing 
season. The samples were analyzed for organic carbon by wet combustion, 
total nitrogen by Kjeldahl, available phosphorus by the Bray No.1 method 
and ammonium acetate extractable cations, e.g. Ca ++, Mg++ and K +. 
Nutrient losses in the eroded sediments will be discussed in two 
sections. The first deals with nutrient losses as affected by different 
cropping sequences and soil-management practices. The second deals 
widl the effects of different mulch rates on nutrient losses. 
96 Soil erosion problems on an alfisol in Western Nigeria 
Effect of Cropping Sequence and Soil Management on N14trient Losses in 
Eroded Sediments. 
Total Nutrients : 
Total annual nutrient losses, the sum of the N, P, K, Ca and Mg 
losses , during 1973 are shown in Figure 11.1. Total nutrient losses in 
eroded soil from the mulch and no-tillage treatments were negligible. The 
total annual nutrient losses from the bare-fallow plots ranged from 65 kg/ 
ba from the 1% slope to 600 kg/ba from the 10 and 15% stopes. Annual 
nutrient losses from the maize-maize (conventional plowing) plots were 
9 kg/ha from the 1% slope and 140 kg/ha from the 15% slope. Similar 
losses from the cowpea-maize plots were 5.6 kg/ha from the 1% slope and 
210 kg/ha from the 15% slope. 
_ ..... ' ':IIe!. 
~ ,..._ •• 1'.'. ..... . 
~OI:lW. ___ t. ....)  
..... , .. 0 II II 13 .. I!I 
Fig. 11.1 Effects of slopes and crop rotations on total nutri ent loss in 
eroded sediments during 1972. 
Total annual losses of organic carbon during 1972 and 1913 are 
shown in Figures 11.2 and U.3. Because erosion losses were high during 
1973, so were the nutrient losses in eroded sediments. Organic C losses 
from the bare-fallow plots varied from 54 to 1030 kg/ha during 19'72 and 
(rom 400 to 3080 kg/ha during 1973. There were no significant differences 
in the losses of organic C from the maize-maize or cowpea-maize plots. 
Mean annual losses ranged from 20 to 200 kg/ha during 1912 and 40 to 
900 kg/ha during 1973. 
Nutrient loss in eroded sediments 9] 
10 1111 
-- - ...............1 .- . 
a.--c ...... _ ..... 
i 
; 
1 
i 
1..  
II • I M 
••e  ... 
Fig. 11.2 Total loss of organic carbon in the eroded sediments in 1972. 
-_.... ...... .. .. ---.. 
~ ...,..-.... 
. 
! ~o 
1 ~ 4 , • .7. . ,. • "" • C '1 • ~ ~ • 
Fig. 11.3 Total loss of organic carbon in the eroded sedirrents in 1973. 
98 Soil erosion problems on an alfisol in Western Nigeria 
Loss of Differrnt Plant Nutrients: 
Losses of various plant nutrients during the first and second growing 
seasons of 1972 and 1973 are shown in Tables 11.1, lL2, 11.3,and 11.4. 
Because the soil~management treatments were more effective during 1973, 
the results for that year only will be discussed here. 
Total N losses from the bare-fallow plots during one season ranged 
from 2S kg/ha from the 1%  slope to 220 kg/ha from the 15% slope. Second 
season losses were lower than first season losses. Total N losses from 
the maize~maize plots varied from 4 kg/ha fIOm the 1% slope to 38 kg/ha 
from the 15% slope. Similar losses from the cowpea-maize plots were 
2.4 kg/ha from the 1% slope to 16.0 kg/ha from the 15% slope. Losses of 
available P were small compared to those of N. P losses ranged from 1. 5 
to 9.8 kg/ha from the bare~fallow plots, from 0.2 to 1.6 kg/ha from the 
maize~maize plotsand from 0.15 to 1.0 kg/ha from the cowpea~aize plots. 
Losses of eXChangeable cations were generally high. K losses varied 
from 2.2 to 16.7 kg/ha from the bare~faUow plots, hom 0.4 to 4.2 kg/ha 
from the maize~maize plots and from 0.2 to 2.0 kg/ha from the cowpca~ 
rnai ze plots. Ca losses were much higher than Mg losses. 
Slope Length and Nutrient Loss in Eroded Sediments: 
Nutrient losses from the maiz.~cOwpea plots as affected by degree 
and length of slope are shown in Tables 1l.S, 11.6, ll.] and 11.8. In 
general, nutrient losses were proportional to soil losses. Total N losses 
during 1973 varied from 26 to 45 kg/ha under maize and from 2 to II kg/ha 
under cowpeas. Simi lady, losses of a vaiIable P ranged from 1 to 2.8 kg/ha 
under maize and from 0.1 to 0.5 kg/ha under cowpeas.Losses of exchange, 
able K ranged from 2.7 to 6.0 kg/ha under maize and from 0.2 to 1.0 kg/ba 
under cowpeas. 
(8) E(fects of Mulching Rates on Nutrient Losses in Eroded Sediments . 
Losses of organic C in eroded soil as affected by slope and rate of 
surface mulching are shown in figures 11.4 and H:S. Because there was 
no soH erosion from plots mulched at the rate of 6 t/ha or from the no~ 
tillage plots there was no loss of soil organiC matter. Losses of organic 
C during the first season varied from 200 to 1000 kg/ha from the unmulched 
plots , from 16 to 100 kg/ha from plots mulched at the rate of 2 t/ha, and 
from 10 to 15 kg/ha from plots mulched at the rate of 4 t/ha. Similar 
losses were recorded during the second season (Fig. 1 L 5}. 
Table 11.1. Nutrient loss in eroded 50il (kg / hol os offected by different sl ope and soi l management treatments. 
I Fi rs t Season . 19721 . 
Treat 1% S% !ax, 15% 
menr 
O. C N03·N Bray EK eh. E.·ch. [ xch. O.C N03 ·N Br<1y Exch. E. .: It. Exclt. O.C N03 ·N Bray Exch. Exch. E.<eh. O.C N03·N Bray Exelt. Exeh. Exeh. 
p Ca Mg K P Ca Mg K P CD My K P C8 My K 
1 25.4 0.06 0 .12 10.2 1.3 0.9 322 .6 0.15 0.6 41.7 5.9 4.8 350.n 0.21 G.71 50. 1 10.4 7.3 892.8 0.6 1.5 101.0 21.7 15.8 
2 T T T T T T 1.6 (l.OO l 0.01 0.7 n.03 0.04 2.1 0.0004 0.001 0.2 0. 04 O,OJ 2.0 0.001 0.001 0.3 0 .04 U.O:J 
3 2 1. 2 U.003 0.04 2.4 0.41 0.4 4B.l U.OOI U.06 4.6 0.8 0.5 92.G 0.02 0.05 10.5 1.7 1.2 173.5 0.07 0 ..3  29,5 4. 2 2.9 
4 f. .l 0.002 0.01 0.8 0.10 0.06 28.3 0.015 0.0f; 3.8 0.4 0.7 100.4 0.04 0.3 11.3 2.3 1.2 137,7 0.09 0.33 20.2 2.2 1.7 
5 1.9 0.001 0.0/14 0.3 0.04 0.04 12.5 0.004 0.03 1.9 0.2 0.2 32.6 0.02 0.05 5.5 0.9 0.5 29.0 0.001 0.01 3.5 n.8 0.4 
T ~ Traces 
Table 11.2 . Nutri ent loss in eroded soi l (kg/ ha) as affected by different slopes and soil management treatmants. 
ISecond Season , 1972 ) 
1% 5% 1~ 15% 
O. C Toral Bray Fxeh. [xeh. [J(eh. O.C Total Bray [xeh. [xch. [xch. O.C Total Bray. [ xeh. [ xeh. Exeh. O.C Total Bray [ xeh. [xelt. [xeh. 
N P Ca Mg K N p. Ca Mg f( N P C8 My K N P Ca My K 
1 28.0 1.69 0.02 1.26 0,12 0,21 254,2 29.3 0.52 13.92 1.28 2.62 490.0 50.73 0.60 24.5 1.63 2.67 403.7 44.8 1.0' 25. 1 1.81 3.48 
2 T T T T T T T T T T T T T T T T T T T T T T T T 
3 2,3 0.22 0.004 O,l~ 0,006 0,018 4.2 1 :4 0.01 0.65 0,05 0.35 29.0 2.01 0.02 0.92 0.07 0.19 63.2 6.14 0.07 4.00 0.16 0.53 
4 T T T T T T T T T T T T T T T T T T T T T T T 
~ B.B 0.97 0.02 0.39 0.03 0.05 40.2 4.1 0.04 2.04 0.13 0.40 34.5 3.53 0.03 1.82 0.12 0.27 198.0 17.20 0.38 13.61 0.53 1.46 
T= Traces 
~ 
Table 11.3. Nutrient loss in erud ~1I ~f.li l it S I'1 fft-~ct~1 by slo' Jf~ dnd soi l ItIflrltlgemPll1. 
(F i rz t Scazon, 1973) 8 
1% 5% 10% 15% 
O,C Total Bray Ex ch. Exch. Ex ch. O.C Totlll Brav E¥.ch. Exch. Exch. O. C TorRI Bra y E.<ch. Exch. Exch O.C Total Bray Exch. Ech. Exch. 
N P Ca Mg K N P Co MfJ K N f' Ca Mg K N P Ca Mg K 
1 269 .9 24.87 1.57 18.0S 0.~8 2.20 100r,.fi n .3fi 4.30 52.2 2.97 0.43 2492.3 198,88 12.r14 151.1 13.67 20.75 2A42.0 217.42 9.82 144.1 13.47 16.72 
2 T T T T T T T T T T T T T I T T T T T T T 
3 45.8 3.47 0.22 2.52 0.14 0.35 193.(> 14 .83 0.87 'l .3E> 0.78 2.14 1078 8.31; 0.70 6.15 0,45 1.10 453.3 37.77 1.61 27.10 2.40 4.24 
4 T T T T T T T T T T T T T T T T T T T T T T T 
5 24.6 2.38 0.15 1.42 O.OS 0.24 107.7 8.37 0.40 B.2l1 0.53 1.67 100.3 6. 95 0.17 12.30 0 .40 1.16 203.7 16.02 0.99 17.37 0.92 1.92 
T~Tr<lces 
Tabl e 11.4. Nutrient loss in eroded soil as "fleeted by s lope and so i l man"gement . 
(Second Sc~son, 1973) 
Treat · 
menl 1% S% 10% 15% 
O.C Total Bray Euh. Exch. Exch. O.C. Total BrAY Fxch. Fxch. Fnh. O.C . TUlnl BrHY E.cl,. Exr:II. E.fCh. O.C . Tutnl 8ray Exci>. Exci>. Exch. 
N P C8 Mg K N P C" M.Q K N P CII Mg /( N P Ca lAg K 
119.6 11.78 0.40 5.37 0.31 0.(>2 1312,0 113.8 5.0 56. 0 3.0 7.28 1139.42 111 .55 7.71 71.57 5,24 7.64 939:04 96.12 3.26 59.03 4.66 12.69 
2 T T T T T T T T T T T T T T T T T T '1' T T T T T 
3 11.6 1.1 3 0.04 0.56 0.04 O.OB 56.40 5.920.16 2.B7 0.24 0.55 60.39 5.13 0.17 3.71 3.73 0.2S 41}4.32 37.53 U.68 25.03 1.8~ 2.93 
4 T T T T T T T T T T T T T T T T T T T T T T T 
5 6:7 0.B9 0.04 0.43 0.03 0.06 79.60 8.36 0.22 4.01 0.39 0.90 74.50 7.15 0.19 4.70 0.32 0.69 868.03 B5.03 2.52 80,62 4.00 5.94 
T .c Traces 
Nutrient loss in eroded sedimenls un 
Table 11.5. Contour length and nutrient loss in eroded soi I (g/ha ). Fi rst 
season 1972 
Nutrient '2.5m 37.5m 
kglha 10.0% 79.296 9.3% 13.4% 
D.C. 342.30 184.10 108.20 143.40 
NOJ-N 0.22 0.08 0.04 0.01 
Bray-P 0.33 0.12 0.11 0.09 
Exch. Ca 50.80 17.00 17.10 14.20 
Exch. Mg 6.60 2.20 2.60 2.20 
Exch. K 5.00 2.30 1.60 1.50 
Table 11.6. Contour length and nutri ent loss in eroded soi I (kg/ha) • 
Second season 1972 
Nutrient 12.5m 37.5m 
kglha 10.0% 19.2% 9.3% 13.4% 
O.C. 93.10 116.00 51 .80 55.10 
Total N 9.10 12.00 -i.58 4.90 
Bray-P 0.10 0.17 0.06 0.05 
Exch. Ca 4.94 6.94 2.59 2.91 
Exch. Mg 0.32 0.38 0.16 0.14 
Exch. K 0.67 0.94 0.36 0.39 
Table 11.7 Contour length and nutrient loss in eroded soil (kg/ha). First 
season 1973 
Nutrient 12.5m .'17.5m 
kgl ha 10.0% 19.2% 9. 3% 13. 4% 
O.C . 563.4 554.0 516 .00 328.10 
Total N 40.69 41.04 45.15 25.36 
Bray-P 2.83 1.93 UE 0.92 
Exch. Ca 35.30 29.39 28.11 17.88 
Exch. Mg 2.72 2.58 1.37 1.65 
Exch. K 5.25 5.$ 4.46 2.66 
102 Soil erosion problems on an alfisol in Western Nigeria 
Table 11.8. Contour length and nutrient loss in eroded soi I (kg/ hal. Second 
season 1973 
Nutrient 12.5m 37.5m 
kglha 10.0% 19.2% 9.3% 13.4% 
O.C. 128.44 19.27 31.00 45.50 
Total N 10.92 l.8S 2.83 4.76 
Bray-P 0.49 0.05 0.10 0.07 
Exch. Ca 6.33 1.35 17.88 3.63 
Exch. Mg 0.44 0.10 0.11 0.17 
Exch. K 0.98 0.18 0.20 0.41 
r.,le'I.9. EHWlol ,.,,oICh ,. 11 : IQIIO.1Ia, ~ "''''If ...... ",,,,,_I .111 .I;Id!'od 50' 
4F,fU'fllOlI l !t74.1 
4J1e1l,.fr '.C  .. ,oo '''' 
J . .. C. ., • C. ., C. ., 
'71 -) .4S. 1.01 '2 .• 
D, 0." _0.1 1.111 10.1 ... ... U .l '.5O II ' 0 64. •• 0 7." ' le.! V lO ,, ~ 13.5 11.~ 
>.0 ' 0.1,0. . C.,. ' .DO 12.3 (l ,1 8 0 ." ...,  (o, Ul ,.r 1), 1; 0 ... l . IS U I 11.6 M' .... . 60 C. !. I 
000 0.002 .. 0 .03 3.002 ,.  e." 0. 11 0 ." (' .015 v 0.0' 0.10 0 .'9 1).0' .., ') .02 O. lD 1.06 0.00 
• , , I ,.  ,n' .10 C .41 ~ .. 10 
fIo.l, lI aO' r 
T.-blll' 1 1, 10, (f'er:: 1 of .. ",Ie'" ,, (e- iIOft"., Dill "",ri_, ClU I .~ i. MOHd 10 '\ 
l SKand 5NlOOI 1fT': 
,. SO .. ,0& ... 
",,,kllt,re " C. .. N C. C. 
 " e, " 
11.4 0.'" ,.., .. , 0. Z2 n .' I. " 
 ". ... .. 1.2 1 l2.D 
0.07 n .D .. " 0 .. .... 0 .2. 10 .6 'O.."ll 2.18 1:2.' 1.11 .... I .CO 2.1' 11 .' ,. . 
l .' ..., 0.12 I.'  " I> !.' D." .U ..3 0 ,.. . 2'!!.7 1.31 
C. l ..... IJ.U 0.10 0.007 ),eO ....... 0 .19 1.67 O.TO 10,0 0." 0." '.2 0." HI .. ., 0.'" 
r  '.' 0." 
T T T r T 1.2 {'I,O' 0. 1 ..• .., 
Ng..1 1 1 ~p r , T r 
Losses of varicus plant nutrients in eroded soil as aHectcd by slope 
steepness and mulch late are shown in Tables 11.9 and 11.10. During the 
first season, N tosses ranged from 27 to 126 kgjha from th e unmulched 
plots, from 2 to 12 kg/ha from the pINS mulched at the rate of 2 t/ha . 
The maximum loss of available P was only 3.5 kgjha. During one season , 
the maximum loss of exchangeable K was 12 kg/ ha; that of Ca,8.4 kg/ha ; 
and that of Mg 11, kg;ba. Nutrient losses during the second season were 
lower than those during the first, but the trends in relation to mulch rates 
and slope steepness were the Same. 
Nutrient loss in eroded sediments 103 
_0 ",",_ 
~ t '_/N 
-- ...../ f. 
~, ......' h:I 
1•  
, 000 
, • ~ 10 II It J' 14 I ' 
Fi g. 11.4 Effect of mulch rates on total loss of organic carbon in the 
eroded sediments in the second season, 1974. 
'E COfoID 'USON , lin. 
0 ... 
.t I ..../ Ita 
• -I. ­"'" 
///  
I"" / 
,/ 
/ 
! , 
t / 
• / 
/ 
.! 10 
/ 
/ / 
/ 
Fig. 11.5 Effect of mulch rates on total loss of organic carbon in the 
eroded sediments in the second season, 1974. 
104 Soi I erosion problems on an alfisol in Western Nigeria 
Table 11.11 Effect of contour length on nutrient loss (kglfla) in eroded 
soil: (First season 1974) 
Nutrient 12.5m /OIUJ 37.5 m lanOg 
kglha 10. C!J6 79.2% 9.3% 13.4% 
0
Organic C. 1314.6 761.0 1314.S 1352.8 
N 145.4 84.1 129.2 135.3 
P 1.2 0.8 2.2 1.2 
K 24.7 g.7 15.2 13.2 
r.a 95.7 55.9 98.1 93.2 
Mg 12.1 9.6 11.5 14.7 
Table 11.12. Effect of contour length on nutrient loss (kgli1a) in eroded 
soil: (Second season 1974) 
Nutrient '2.5m long 37.5m long 
kglha 10.0% 19.296 9.3% 13.4% 
Organic C. 613.7 440.7 796.4 679.2 
N 56.B 48.7 96.5 68.7 
p 0.38 0.10 0.91 0.35 
K 3.4 2.3 4.7 3.4 
Ca 34.7 24.2 51.7 42.2 
Mg 4.0 3.7 5.7 5.3 
Contour Length and Nutrient Loss: 
The effects of contouI length and slope steepness on nutrient losses 
in eroded soil are shown in Tables 11.11 and 11.12. The trends innuUient 
losses are similar to the uends in soil losses presented in Chapter 6. 
Maximum nutrient losses during one season were 145 kg/ha of N. 2.2 kg! 
ha of p. 25 kg/ba of K. about 100 kg/ha of Ca and lSkg/ha of Mg. 
Nutrient loss in eroded sediments IDS 
REFERENCES 
1. Ensminger, L. E. (1952). Loss of Phophates by erosion. Soil 
Sci. Soc. Amer. Proe. l6~ 338-342. 
2. Ensminger,L. E. and J. T. Cope (1947). Effect of soil reaction 
on the efficien\.y of various phosphates for cotton and on 
to 58 of P by erosion. ]. Amer. Soc. Agron. 39: 1-11. 
3. Gupta, R. N. and N. Singh (1967). Selectivity of erosion pro­
cesses with respect to soil phosphorus in the alluvial 
tracts of U. P. J. Indian Soc. Soil Sci. 15: 261-268. 
4. Kowal,J. (1972). The hydrology of a small catchment basin 
at Samaru, 'Jigeria. IV. Assessment of soil erosion under 
varied land management and vegetation cover. Nigeria 
Agric. J. 7: 134-147. 
5. Massey, H. F.,M. L.Jackson and O. E. Hays (1953). Fertility 
erosion on two Wi sconsin Soils. Agron. J. 45: 543-547. 
6. Osborn, W. M• • and O. R. Mathews, 1955. Crop rotation, tillage 
and fertility experiments at Lawton field station 1917-49. 
r. S. D. A. Cor. 951 : 58. 
7. Rogers, H. T. (1944). Plant nutrient losses from a com, wheat. 
clover rotation on Dunmore Silt loam, Soil Sci. Soc. Amer. 
Proc. 6: 263-271. 
B. Scarseth, G. D.,and W. V. Chandler (1938) Losses of phos­
phate, from a light te.·dured soil in Alabama and its rela­
tion to some aspects of soil conservation. Agron. S. 30: 
361-375. 
9. Thomas. A. W., R. L. Carter and ]. R. Carreker (1968). Soil, 
water and nutrient losses from Tifton Loamy Sand. Trans. 
ASAE 11: 677-679. 
lO. Volk, G. W. (1945). Response to residual phosphorus of cotton 
in continuous culture. Agron. S. 35: 330-340. 
• 12 
Hogers (1944) reported that lhe eroded material from com land was 
richer in nitrogen and phosphorus than the original soil. The enrichment 
ratio, the ratio of plant nutrients in eroded soil to those left behind in 
the soil, has been discussed by various workers (Fippin, 1945; Massey 
and Jackson, 1952; Barrows and Kilmer, 1963). Barrow and Kilmer re~ 
ported that soil P is primarily lost through eroded sediments. Information 
on the phYSical properties of eroded sediments in relation to the parent 
soil and the changes in soil physical properties as a result of erosion 
for tropical soils is lather scarce. (Jones and Wild , 1975). 
A. Soil Physical Properties 
(a) Ter/ure. The textures of the surface samples of the soil at the 
beginning of these studies in February 1972 and in February 1974, and 
of soil samples eroded wring the first season o( 1973 are shown in 
Figure 12.1. Although the texture of the plots of treatments 2 and 4 did 
not change, there were significant changes in the particle size distribu~ 
tion among the treatments 1, 3 and 5 between 1972 and 1974. The most 
dramati c changes in soil texture were in the bare~(a\low plots , where 
there was a marked increase in gravel content during the two years. 
The gravel concentration in the eroded sediments was only slightly 
affected by degree of soil slope (Figure 12.2). Sand content, however, 
increased with increase in slope. The sand content of the eroded sample 
increased from 33% on the l~percent slope to 66% on the IS-percent 
slopeo The most erodible particles on the 5, 10 and IS-percent slopes 
were sando The silt and clay contents of the eroded soil decreased with 
increase °in slope. The silt conlent decreased from 25% to 9% and the 
clay content from 27% to 12% as (he slope increased from 1 to 15 percent. 
The change in particle size distribution of the eroOded soil with change 
in slope may be due to the increased velocity of runoff water at steeper 
slopes and thus its increased capacity to transport coarse particles. 
The erosion ratio indicates that silt~plu~clay content of the eroded soil 
was generally higher than that of the field soil. The erosion ratio was 
significantly lower for 10 and IS-percent slope plots than for the 1 and 
108 Soil erosion problems on an alfisol in Western Nigen"a 
2 3 ~ 
Fig. 12.1 Changes in the textural conposition of surface soil from 1972-
1974 as compared to that of the eroded sediments. 
S-percent slope plots (Table 12.1). The crop rotation did not signifi~ 
cantly affect the erosion ratio, altbough the values were low {or bare­
fallow plots. 
(b) Soil Mo isture Characteristics. Soil moisture retention character­
istics of the eroded and field soil for different treatments are shown in 
Figure 12. 3. The eroded soil had a higher moisture retention capacity at 
all suction ranges than the field soil and this can be attributed to the 
higher silt, day and organic matter contents of the eroded soil. The 
moisture retention capacity of eroded soil from l~, >-, 10- and IS-percent 
slope maiz.e-maize (conventionally plowed) plots respectively were 0.41, 
0 .50,0.45 and 0.55 gg-l at 0.1 bar suction compared to 0 .25,0.24 , 0.25 
and 0.25 gg-I for the field soil. A similar trend in moisture content is 
obvious for other suctions as well. The eroded soil from the bare~fallow 
plots had a lower moisture retention capacity than the eroded soil from 
the maize~maize or cowpea-maize plots. 
The data on soil moj sture equi valent follow the same nend (Table 
12.2). The mean. soil moisture equi valent of the eroded soil was 31.1 % 
compared to 16.2% for the field snil. The mean soil moisture equivalents 
of the eroded soil (rom the bare-fallow plots (J8.3%) were lower than 
those of the eroded soil {rom the mai2;e-tnaize (26.0%) or the cowpea­
maize (24.9%) plots. 
Properties of the eroded 'sediments in relation to the original soil 109 
70 
32 
28 
2 
4 
16 
SIOpe% 
Fig. 12.2 Influence of soil slope on concentration of gravels, sand, silt 
and clay in the eroded sediments. 
Table 12.1. The erosion ratio as affected by slope and soi I management 
treatments. 
Treatment Slope % Mean 
1 4.62 1.34 1.03 1.23 2.06 
3 3.44 2.38 1.02 2.74 2.40 
5 3.14 2.73 1.69 1.61 2.29 
Mean 3.73 2.15 1.25 1.86 
Erosion Ratio = silt + clay of eroded sedimentsl (silt + clay of field soil) 
gravel + sand gravel + sand 
110 Soil erosion problems on an alfisol in Western Nigeria 
It 10% Ie% 
1% ~ e% 
............ MabIt ~ Malz.t 1 Er""-cl 5<111 
\\ I-I Co.pea-M 
<>---<> aa.. folloW r 1 I  i\ 1 
l 
~ 
<II 1 
i~ I 
... 
lii 
~I 
~ 
i 
...l Feild Soil 
~15 1 111 1 It 
~ 
:t I 
·1 .I! ·3 -4 ·5 ·5 · 1 ·2 "'4 ·5 ·1 ·!·3 .. ·e ·1 -2 '3 -4 -~ 
SolI M.i_ Coft!On1 (,,-I, 
Fig. 12.3 Soil moisture retention characteristics of eroded soil as com­
pared with that of surface soil samples obtained from the run­
off plots. 
Table 12.2. Soil moisture equivalent (99-1) of the eroded sediments as compared to 
the field soil . 
Treatment Soil moisture equivalent for different slopes 
1% 596 1( 1)6 '!!I(, Mean 
ES FS ES FS ES FS ES FS 
1 0,146 0.182 0.117 0.286 0.115 O.2B7 0.149 0.183 
3 0.281 0.174 0.386 0.197 0.266 0. 163 0.407 0.203 0.260 
5 0.359 0.141 0.356 0 .201 0.306 0.151 0.299 0.181 0.249 
Mean 0.320 0.154 0.30B 0 .172 0.286 0. 143 0 .331 0.178 
ES= Eroded sediments 
FS= Field soil 
B. Soil Chemical Properties 
(a) Enrichment Ratio. The enrichment ratio data for different tteat~ 
ments are shown in Table 12.3. The enrichment ratio is high for organic 
C and P. Except for P , the enrichment ratios for oth er nutrients are 
lowest from the bare-fallow plots. This may be du e to the dilution effect 
resulting from greater erosion losses from the bare-fallow plots. The 
Properties of the eroded sedim ents in relation to the original soil 111 
Table 12.3. Average enrichment ratio for different nutrients. 
Treatment D.C. N p K Ca Mg 
1 2.21 1.54 5.96 1.36 1.52 1.12 
3 2.75 1.73 5.55 2.02 1.45 1. 16 
5 2.22 1.65 5.83 1.62 1.62 1.23 
Each value i s average of 16 figures for 4 slopes and 4 growing seasons. 
5 
ORGANIC CARBON 
I 
a 
~ 
It: 
TOTAL NITROGEN 
o 
Jon 1973 July 1913 Jan 1974 
TIME 
Fig. 12.4 Changes in the enrichment ratio of organic carbon and total 
nitrogen with t irre. 
enrichment ratios of organic C and N decreased with lime after forest 
dearing (Figure 12.4). The average enrichment ratio for organic C was 
4.25 in August 19]2 and 1. 5 in J anuaty 1974. 
112 Soil ero.sion prrhlems on an olfisol in Westem Nigeria 
Similarly, the average enrichment ratio fur N decreased (rom 2.0 in 
January 19'J3 to 1.4 in January 19'J4. Gradual decline in organic C and 
total N contents of soil may account for the decrease of enrichment 
ratios wi th time. The enri clunent ratios of other elements did not follow 
any trend with lime after forest clearing. 
N 
~A 
~-----~-
2 
Slope ,. 
Fig. 12.5 Effects of soil slope on the enrichment ratio of some nutrient 
elements. 
Soil slope had a significant effect on the enrichment ratiosof certain 
elements (Figure 12.5). The average enrichment ratio of organic C, N, P 
and K decreased with increase in slope. The enrichment ratio of organic 
Table 12.4. Soil r:hflnlical properties. February 1972 
Treat· 5 10 75 
ment pH O.C. N P K Co Mg pH O.c. N· P K Ca Mg pH O.C. N P K Ca Mg pH O.C. N P K Ca My 
6.5 2.7 0.25 78.4 0.77 3.5 1.5 6.4 1.90 0.14 31.9 0.32 2.5 1.0 7.0 2.1 0.18 31.9 U.25 3.5 1.6 7.32.50.2453.90.673.102.3 
2 6.7 2.9 0.27 85.8 0.56 3.5 1.5 6.9 2.30 0.1 B 44.5 0.56 2.3 1.4 6.9 2.4 0.23 41.30.32 3.0 2.3 7.3 2.1 0.21 44.5 0.56 4.3 2.2 
3 6.3 2.5 0.23 96.9 0.56 3.5 1.4 6.7 2.20 0.17 35.0 G.56 2.3 1.2 6.8 2.5 0,20 44.5 0.32 2.5 1.6 7.1 2.2 0.19 54.90.233.0 Ul 
4 6.4 2.3 0.21 81.9 0.56 3.0 1.7 6.9 2.70 0.19 44.5 0.77 2.5 1.7 6.7 2.0 0.16 47.6 0.56 3.5 1.9 7.1 2.3 0.21 47.60.564.0 2.1 
5 5.5 2.7 0.21100.8 0.67 3.3 1.7 6.7 2.30 0.19 31.9 0.67 1.8 1.3 6.8 2.0 0.24 37.8 0.56 2.8 1.8 7.5 2.7 0.25 53.9 0.56 3.5 2.2 
February 1974 
1 5.0 1 .30 0.1 5 5.0 0.43 6.4 1.2 4.8 0.95 0.11 4.8 0.48 3.6 0.95 4.7 1.15 0.11 4.7 0.36 4.2 1.1 4.2 1:1 0.11 4.2 0.10 4.0 0.58 
2 6.0 2.85 0.24 6.0 0.56 9.7 1.7 6.0 1.90 0.13 5.3 0.61 4.6 1.00 6.0 2.10 0.20 6.0 0.82 7.7 1.9 5.8 2.5 0.14 5.3 0.46 8.2 i,92 
3 5.6 1.60 0.17 5.6 0.46 7.6 1.5 5.3 1.20 0.1' 5.3 0.31 3.6 O.SS 5.7 1.91) 0.135.8 0.51 7.1 1.8 5.3 1.4 0.12 5.3 0.10 6.4 1.73 
4 5.5 2.1 0.22 5.5 0.78 9.8 2.1 5.7 1.65 0.13 5.7 0.46 4.9 0.B4 5.8 2.20 0.20 5.8 0.67 7.8 1.5 5.6 2.1 0.19 5.5 0.78 B.O 1.79 
5 5.B 1.750.14 5.8 0.47 8.6 2.0 5.8 1.65 0.13 5.B 0.46 5.5 1.4 5.9 1.90 0.17 5.9 0,56 7.6 1.6 5.8 1.9 0.16 5.8 0.41 8.4 1.65 
-tJ 
114 Soil erosion problems on an alfisol in Western Nigeria 
C decreased by 0.66 for each percent increase, that of N by 0.017, that 
of P by 0.14 and that of K by 0.04. This decrease in enrichment ratio 
with increase in slope may be due to the coarse nature of the eroded 
sediments from the steeper slopes compared to higher clay and silt con­
tents of the eroded soil from the gentle slopes (Figure 12.1). 
(b) Soil Chemical Properties. The chemical properlies of the surface 
soil immediately after forest clearing in February 1972 and two years 
later, in February 1974, are stlOWt1 in Table 12.4. rn general, there was 
a decrease in soil pH, organic C, total N, available P and exchangeable 
K. The decreases in organic C, total N and K contents were negligible 
for mulched and no tillage treatments. 
Table 12.5. Effect of scil management and croppjng sequence on chemical charac-
teristics of the soil (O·1 0cm layer) July 1974 
Treatment pH Organic Total BrBy·1 CEC Exchangeable cation (meqI 100 gJ 
carbon nitrogen P (meqI100J Ca ++ 41g++ K.. . 
% % (ppm I 
Bare fallow 5.10 1.32 0.079 41.87 7.22- 5.04 0.63 0.46 
Mai ze-maize 
(plowed) 5.35 1.30 O.<l96 42.52 8.D7 6.10 0.94 0.58 
Maize·cowpea 5.50 1.00 0.143 62.65 9.07 6.62 1.13 0.76 
(No-ti 11age) 
Maize-ma i ze 5.60 2.10 0 .148 54.86 10.42 7.74 1.36 0.88 
Imulch) 
Some chemi cal characteristics of the soil analyzed during July 19; 4 
are shown in Table 12. 5. The values arc averaged over aU slopes. Soil 
pH organic C content, CEC, exchangeable cations, available P and local 
N were in the following order: bare-fallow, maize--maize (plowed), maize­
cowpeas (no-tillage), maize-maize (mulched). Mulching and minimum 
tillage treatments by preventing soit erosion,maintained chemical rertility 
of the soil. 
Properties of the eroded sediments in relation to the original'soil 115 
REFERENCES 
1. Barrows, H. L., and Kilmer, V. J., 1963. Plant nutrient losses from 
soils by water erosion. Adv. Agron. 15:303-316. 
2. Hudson, N.W., and Jackson, D.C. , 1959. Results achieved in measure­
ment of erosion and runoff in Southern Rhodesia. Proc. 3rd 
Inter- Afli can Soils ConL, Dalaba, 1959. 
3. Fippin, E. 0.,1945. Plant nutrient losses in silt and water in the 
Tennessee River S~'stem, Soil Sci . 60:223-239. 
4. Jones M. J .,and A. Wild, 1975. Soils of the West African savanna. 
Tech. Comm. 55, C. A. B. Farnham Royal. 
5. Latterell, J.J., Holt. R. F. ,and Timmons, D. R., 19i 1. Phosphate a vail­
ability in lake sediments. J. Soil and Water Conserv.l: 21-25. 
6. Massey,H.F. ,and Jackson,M.L.,19S2. Selective erosion of soil fer­
tility constituents. Soil Sci. Soc. Amer. Proc. 16: 4. 
7. Rogers, H. T. ,1944. Plant nutrient losses from a com . wheat, clover 
rotation on Dunmore Si It loam. Soil Sci . Soc. Amer. Proe. 
6: 263-271. 
• 13 
The degree of soil erosion that can be tolerated depends upon the 
depth of surface soil, the nutrient status and physical properties of the 
subsoil, and the nature of crops to be grown. For shallow tropical soils 
derived from basement complex rocks, a loss of a few centimeters of 
surface soil may result in serious yield reductions. Little quantitati\;e 
infonnation on the effects of soil erosion on crop yields exists. This 
chapter descri bes the magnitude of the effects of soil erosion on soil 
physical properties and crop yields. 
Two major effects of soil erosion are degradation of soil physical 
properties and loss of plant nutrients, roth applied and inherent. One 
major nutrient lost in eroded soil is applied phosphorus ( Ensminger , 
1952; Gupta and Singh, 196]; Scarseth and Chandler, 1938 ; Volk, 1945). 
Losses of N and other nutrients in eroded soil have also been reported 
by various workers (Kowal, 1972 ; Massey et aI, 1935; Osborn and Ma th('ws 
1955; Rogers, 1944). 
I~eports concerning the effects of soil erosion on crop yields vary. 
Although the majority indicate yield depressions (Doshchanov and 
Muratova, 1953; Filipovic, 1968; Pasevct aI., 1968 ; Tikhonov, 1960; 
Transhliev and Tikhonov, 1963), some report a temporary increase 
(Grosse, 19(7). In the latter study , the loss of organic matter in eroded 
soil was at least temporarily compensated by better phy sica} conditions 
of the exposed subsoil. 
In the studies reported here changes in grain yield over time as 
affected by various treatments and the effect of arti fi cially removing soil 
on the grain yields of maize and cowpeas were investigated. Varying 
depths of surface soil from an Egbeda series soil were removed and the 
growth and development of maize and cowpeas were observed. 
Changes in soil nutrients and in soil fertility status have already 
been discussed in Chapter 11 and l2. Changes in the ph)·sical char­
acteristics of thf soil as a result of soil erosion and crop response will 
be discussed in this chapter. 
118 Soil erosion problems on an alfisol in Western Nigeria 
60 
550 
Bore folio"., 
500 
450 
400 
350 
300 
250 
200 
150 
c 
.2 
~ 
~60 Maize - Maize (Coovenlional Tilla9') 
.£ 
~550 
~500 
§ 
v~50 
40 
350 
300 
250 
2 
25 50 7~ 100 125 150 175 200 25 175 20 0 
I Time (Min) 
Fig. n.1 Infiltration capacity ot the soH as influenced by time after 
forest clearing under different soil management and crop rota­
tion treatments. 
hlfiltra tion RIlIt' . Infiltration rates of the soil on th e lO-p ercent slop e 
plots, measured during the dry seasons of 1972. 1971 and 1974. are 
shown in figure 13. 1. In general. the in filtration rate de creased with 
time. In bare- fallow plots th e infiltration rares after two hours were 
3.5 em min,l , 1.5 em min'l and 0.2 em min#l fot 1972, 1973 and 1974. 
Changes in soil physical characteristics and crop yield as a result" 
of erosion 119 
6 
t:l 
Percent Grovel Percent Sand 
60 
0------01% 
K-ll ~". 
~ 10". 
I!l----G 15% 
.O.J.  
'0; 
Percent Silt Ptrcem Cloy 
l 
o 
8 
6 
2 
o 3 6 9 12 15 18 21 24 0 :3 6 9 12 15 18 21 22 24 
Time (months) 
Fi9.13.2 Changes in texture of the soil in bare fallow plots during 
1972..,...1973. 
respectively. Similar values were 3.5 cm min#l, 1. 5 em min#l and 0.6 em 
min·1 in the maize-maize (mulched) plots; 3.5 cm min-l , 1. 5 em min'1 
in the maize-co~ea (no-tillage) plots; and 3.5 em min-I, 1.75 em min -[ 
and 0.1 em min#l in the maize-maize (plowed) plots. The infiltration rate 
decreased from an initial rate of 3.5 em min#} to 0.1 em min'} in the 
maize-maize (plowed) plots, to 0.2 em min in the bare-fallow pIOIS, 
120 Soil erosion problems on an alfisol in Westem Nigeri a 
to 0.6 em min~l in the maize~maize (mulched} plots and to 1.5 em min ~1 
in the maize~cowpea (no~tillage) plots. If the erosion process continues 
on the bare~fallow and maize~maize plots, the exposed subsoil of low 
penneability may further retard the infiltration rate. On the other hand, 
the concentration of gravel on the soil surface as a result of erosion 
could improve the infiltration rate, particularly in the lS~percent slope 
plots. 
Soil Texture. Changes in texture of the soil in the bare-fallow plots are 
shown in Figure 13.2. The trend indicated in th e graph may be. reversed 
if erosion continues and heavier textured suhsoil is exp\)sed. This has 
happened in some plots. In general, there was an increase in gmvcl 
concentration in the surface soil of all the bare~fallow plots. On the 
~percent slope plot the gravel content increased from 5 to 25% over two 
years. The greatest increase from 30 to 55% occurred in the 1 'Ypercent 
slope plot wi th a proportionate decrease in the sand, silt and clay frac­
lions. Un the ~percenl slope plots the clay content of the surface hori~ 
zon decreased from 23 to 16%. On an average the day content of the 
surface horizon decreased 5 to 6%; the stlt content, 2 to 4% ; and the 
sand content, 10 to 15%. 
Moisture Characteristics. The decreased organic C and silt and day 
contents Ihat resulted (rom soil erosion are reflected in the moi311HC 
retention characteristics of the soiL (Table 13.1). The moisture retention 
at zero suction of the soil in the bare-fallow plots on the I5-percent 
slope decreased from 40% in 1972 to 28% two years later. Similar de~ 
creases in moisture retention were recorded at all suctions. The moisture 
equivalent values decreased from 19% in 1972 to 10% in 1974. A similar 
trend in the moisture retention characteristics of soil in the bare-fallow 
plots on oth.et slopes was observed, although the magnitude of the reduc­
tion in moisture retention capacity was less on the gentler sLopes. 
The effects of soil management on the moisture re tention charac~ 
teristics of the soil in the ~percent slope plots are shown in Figure 
13.3. Moisture retention at all suctions was highest in the mulched and 
no~tillage plots followed by that in the conventionally plowed maize 
plots. The soil in the bare~fallow plots had the lowest water-holding 
capacity. The moj·sture retention at zero suction was 30% in the bare­
fallow plots , 34% in the conventionally plowed maize plots and 36% in the 
mulched ;l.nd no-tillage maize plots. 
Crop Response. Maize yields as affected by dif(erenl slopes and man­
agement practices are shown in Figure 13.4. Although the ~' ields on the 
no~tillage plots were equivalent to aT higherthan those on the mulched 
Changes in 'soil physical characteristics and crop yield as a result 
of erosion 121 
Table 13.1. Soil moisture retention at differe rlt suclions for bare fallow plol al 
24 percent slope. 
Time Soil moisture cootent (gg -1) at different suctions I bars J 
o 0.1 0.3 0.4 1.0 2.0 3.0 15.0 moisture 
equivalent 
Feb. 1972 0.300 0.121 0.084 0. 188 
Dec. 1973 0,241 0.161 0.134 0.118 0.118 0.090 0.150 
Aug. 1973 0.359 0.140 0.110 0.115 0.106 0. 103 0.095 0.075 0.127 
Jan.1974 0.279 0.145 0 .123 0."9 O.'O~ 0.092 0.005 0.076 0.100 
5"1. SlOPE 
(!)..-..() BarE fal low 
11.----. Moize-Main (CoM&ntionol Plan) 
6---4 Maize-Maize (Mllicned) 
0--0 MoiZll- Maize ~ lIIo-Tillcge) 
2 .:3 4 
Soil Moi.tur. Content (ocrl) 
Fig. 13.3 Soil moisture retention characteristics as influenced by soil 
management and crop rotation treatments. 
122 Soil erosion problems on an alfisol in Western Nigeria 
1-6 
1% Slope 5"1. Slope 
I -
1-4 x-x Maize (Plawedl 
0 --0 Maize(No-tlllo~el 
1-3 b_& Maize (Plowed <lfter cowpeas) 
1-2 
I-I 
1-0 
-9 
-8 
-7 
-6 
-!5 
c 
..J 
!!:! 
>- 10". Slope 15'1'. Slope 
w 
~ 1-6 
I-
-<l: 
..J I-I) 
I.IJ 
a:: 1-4 
I-~ 
1-2 
I-I 
1-0 ---~~-----~--- --
-9 ~ 
-8 
-7 
~ 
-6 
Seaeon let Season 2" Seaeon 
1973 
Fig. 13.4 Relative maize yield during 1972 and 1973. 
Changes In soil physical characteristic and crop yield as a result 
of erosion 123 
plots, the yields on the conventionally plowed maize plots declined 
progressi vely over the four growing seasons. Maize grown in rotation 
with cowpeas yielded more than continuous maize. 
B. Effect of Artificial Soil Remvval 
The height of maize and cowpeas was significantly depressed by 
surface soil removal. The combined >'ields of maize and cowpeas for two 
."c  
'- 9 
I-
G 
..,8 G 
"II 
>= 7 
.E 
E 
(!) 6 '" 
.! 5 
2! '" 
4 
2. 
0 
~ . 
>­
.,·6 
<> 
~ 
~5 
<:> 
·3 
:L~ 
o I 2. -C~!'---':"4---'::5!1 ,-----'6,.---±~-.J,.8- -:9~-!:1'o::--+';1- -:1f;::12~13!;--+i4;--~I~'-"'1\::-6 --!:1'7~18 
Oepth of ~) ,emo.ed (em) 
Fig. 13.5 The influence of artificial soil removal on yield response of 
maize (Zea mays L.l and cowpeas (Vigna Unguiculata). 
consecutive· seasons with di fferent depths of soil removed are shown in 
Figure 13.5. Relative maize yields were 77, 62, 51, 47 and 44% of the 
yield on the control plots when 2.5, 5.0, 7.5, 10.0 and 12.5 em, respec' 
124 Soil erosion prob/ ems on an al/isol in Western Nigeri a 
tively, of soil were removed. Removing 2.,5 em of surface soil has a 
greater detrimental effect on maize yield than on cowpea yield. 
Weekly measurements of soil moisture content on these plots showed 
that the control plots had higher moisture contents than the others. There 
were no significant di.fferences in soil moisture content among the plots 
when different depths of soil were removed. 
Bulk densities measurement of the surface soil after removal showed 
that exposed subsoi'l became compacted within a short period. Measure~ 
mcnts made four weeks after planting showed bulk densities ranging from 
1. 28 in plots from which no surface soil was removed to L.43 in plots 
from which 5.0 cm of surface soil was removed to 1.45 in plots from 
which 7.5 em of surface was removed to 1.43 in plots from which ID.O 
cm of ~lJrface soil was removed and to 1.45 in plots from which 12.5 em 
of surface soil was removed. The root growth of maize and cowpeas was 
Table 13.2. Effect of depth of soil removed on root development 
De~rh Maize Co"'~e,,s 
of soil Root Average Max. lIneral Dry Root Average Max. Lateral Dry 
removed number length depth spread wei{/lf number length depth spread weight 
(em I (em) l eml (em ) gJ pfarIC (em) len, ) (em) g/ plilnt 
0 51 21, 4 25 55 5,07 IS 10.7 27 29 026 
2.5 24 19 ,8 18 40 1 .24 10 7.4 17 10 0 ,1 1 
5.0 24 15.3 13 50 1.03 10 9.1 25 12 0 ,1 1 
7.5 20 18 ,1 14 40 0.7 1 9 8.2 30 11 0 .11 
10.0 22 13.2 14 35 0.42 8 8.1 24 12 0.05 
12.5 21 15.0 11 35 0.67 9 6.7 12 7 0.05 
significantly affected by soil removal (Table 13.2). Root weight per 
plant was drastically reduced by soil removal. The root weights of maize 
were 24, 20, 14, 8 and 13% of those in the control plots when 2.5, S.O, 
7. 5,10.0 and 12. ') em, respectively, of soil were removed. Similar weights 
of cowpras were 42, 42, 42, 23 and 19% of those in the control plots . 
CONCLUSIONS 
Soil erosion results not only in th e phy sical removal of surface soil , 
but also in losses of organic matter and nitrogen. In addition to nutrient 
losses, the moi sture retention characteri sti cs, infiltration rate are also 
significantly affected. The yield depression that results can be a uri buted 
to degradation of the physical properties of the soil and losses of organic 
matter and soil nitrogt.i1. Physical characteristics of the subsoil may 
oominate the crop response on eroded lands and addition of fertilizer 
may not compensate for removal of surface soil by erosion. 
Changes in soil physical characteristic and crop yield as a result 
of erosion 125 
REFERENCES 
I. Doshchanov ,M. B. , and Muratova,G.G. ,1953. The effect of the erosion 
of upland soils on the yield of agricultural crops. Pochvove~ 
denie N. 8: 75-S1. 
2. Ensminger,L.E.,1952. Loss of phosphates by erosion. Soil Sci. Soc. 
Amer. Proe. 16 : 338-342. 
3. Ensminger,L.E. and Cope,j. T.,1947 . Effect of soil reaction on the 
efficiency of various phosphates for totton and on loss of P by 
erosion. J. Amer. Soc. Agron. 39 : I-II. 
4. filipovic,D.,I96S. Erosion of arable land in the upper jasenica 
watershed and its influence on winter wheat yi eld. Arh. Poljopr. 
Nauk. 21 N. 74: 16-27. 
5. Grosse, B., 1967. The productivity of severely eroded Parabraunerde 
formed from loss under moderate climatic conditions. Trans. 
8th lnt. Con gr. Soil Sci. 1964, 2 : 729-735. 
6. Gupta R.N.,and Singh. N.,1967. Selectivity of erosion processes 
wi th respect to soil phosphorus in the allu vial tracts of U. P. 
J. Indian Soc. Soil Sci. 15:261-268. 
7. Hegyi, G.,1970. Model experiment on erosion in brown forest soil 
su bj eel to clay ilIuvialion. Preliminary report. No ven)' termele , s 
19 : 71-78. 
8. Kowal, J., 1912. The hydrology of a small catchment basin at Samaru, 
Nigeria. IV. Assessment of soil erosion under varied land man~ 
agement and vegetation cover. Nigeria Agrie. J. 7 : 134-147 . 
9. Massey, H. F.,J ack son , M.L.,and Hays, O.E., 1953. Fertility erosion 
011 two Wisconsin Soils . Agroll. j . 45 : 543-547. 
10. Osborn, W. M. ,and Malhews,O. R. ,1955. ClOP rotation, tillage and 
fertility experiments at Lawton field station 1917-49. U.S.D.A . 
Cire. 951: 58 
11. Pasev,P.,Dundakov,P.,and Dekov,L.,l968 . The effect of some soil 
relief conditions and slopes on the growth 0 f vin es and the 
quali ty of grapes and wine. Grad. 10~aI. Nauka 5, No.6: 63-70. 
· 126 Soil erosion problems on an alfisol in Western Nigtri4 
12. Rogers,H. T.,1944. Plant nutrient losses from a com, wheat, clover 
rotation on Dunmore silt loam. Soil Sci. Soc. Amer. Proe.6 : 
263-271. 
13. SC3rseth,G.D. ,and Chandler,W.V.,1938. Losses of pho sphate from a 
light-textured soil in Alabama and its relation to some aspects 
of soil conservation. Agron. J. 30: 361- 375. 
14. Thomas, A. W. ,Carter,R.L.,and Carreker,].R., 1968. Soil , water and 
nutrient losses from Tifton loamy sand. Trans. Amer. Soc. Agr. 
Eng. 11 :617-679. 
IS. Tikhonov,A.V.,I960. Soil erosion and its effect on yield in regions 
of the Volga hills . PochvQvedenie N. 2: 80-86. 
16 . Trashliev,Kh.,and Milchev,M. ,1963. Effect of surface erosion on 
soil properties and on yield of some agricultural crops. lzv. 
lnst. Pochvoznan . Agrotexh. Push'karov. 8 : 213-222. 
17. Volk, G. W:, 1945. Response to residual phosphoru s of cottOIl in 
continuous culture. Agron. J. 35 : 330-340. 

APPENDIX la Run-off and soil loss records for individual rain storms during 1972 
Run-off I mm) losses unn",r slopes and soil management trea tm en ts. 
Rainfall Intensity mmlhr 1% 5% 10% 15% 
Date mm Max . Mea" 2 3 4 5 2 3 4 5 2 3 4 5 2 3 4 6 
2/ 3177 50.8 14.6 0.0 4.9 4.2 4.5 1.6 1.6 25.5 3.7 18.33.7 0.0 14.0 16.45.7 3.7 0.4 4.7 3.7 3.7 
16/ 3/ 72 !',J 0.1 . 0.0 0.1 n.l 0.1 0.1 0.1 0.2 n.1 0.1 0.1 1).2 0.1 0.1 0.1 0.2 0.1 f).1 0.2 0.2 
5/ 4172 12.7 0.5 0.0 0.3 0.2 0.1 0.0 0.2 O}I 0.2 1.1 0.5 0.5 0.6 0,,4 0_5 0.6 0.3 0.6 0.6 0.6 
714/ 72 14.0 0.1 0.0 0,1 0.2 G.£ C.2 0.2 0.4 1.6 0.4 C.2 G.3 0.4 \).3 0.3 0.5 0.3 0.5 0.5 0.6 
14/4/ 72 23.5 0.6 0.0 0.3 0.4 0.3 0.5 0.4 0.6 0.3 0.13 0.4 0.5 0.6 0.6 0.5 0.5 0.4 0.5 0.6 0.4 
20/4/72 13.3 0.9· 0.0 0.9 0.5 0.4 0.8 0.4 2.1 4.0 1.4 0.7 0.7 1.u 1.4 0.8 0.8 0.5 0.8 t.2 1.3 
23/4172 22.2 0.4 0.0 0.8 0.2 0.1 0.5 0.0 1.5 2.6 0.9 0.3 0.2 0.3 0.9 0.2 0.2 0.1 0.2 0.7 0,5 
30 / 4/ 72 10.8 81.28 14.22 0.5 0.0 0.3 0.3 0.1 1.4 0.1 1.8 2.0 1.8 0.5 0.2 0.5 0.4 0.4 0.3 0.2 0.3 0.4 0,5 
415172 20:0 60.96 23.11 0.8 0.0 0.3 0.2 0.1 0.6 0.2 1.8 2.1 3.6 0.6 0.5 0.6 0.7 0.7 0.3 0.3 0.6 0.7 1.3 
8/ 5172 13.3 36.58 7.62 0.6 0.0 0.5 0.3 0.2 0.2 0.2 1.8 O.H 1.7 O.B 0.3 0.6 0.7 0.6 0.5 0.3 0.5 0.6 O.~ 
" / 5172 12.7 30,4S 10.92 O.S (l.a 0.5 0.' OJ 0_7 0-.1 1.3 1.1 2.2 0.3 0.2 0.3 0.4 0.3 0.4 0.2 0.3 0.4 0.7 
14/5/72 13.3 50.80 16.00 0.8. 0.0 0.5 0.2 0.1 3.1 0.1 2.0 1.3 2.3 2.0 0.3 0.6 1.2 0.6 1.2 0.2 0.3 1.2 1.2 
27/ 5/72 5.1 36.57 6.86 0.3 0.0 0.2 0.1 0.1 0.2 0.1 0.3 0.2 0.2 0.3 0.2 0.3 0.3 0_3 0.3 n.3 0.3 0.3 0.3 
28/ 5172 61.0 124.24 33.73 54.5 0.0 3.7 1.4 0.7 42.0 0.6 25.6 12.5 7.3 56.5 1.6 2.8 11.7 2.3 25.6 1.1 2.4 10.5 2.7 
29 / 5172 6.4 40.64 8.38 2.4 0.3 0.5 0.2 0.6 3.0 0.1 1.1 0.6 0.6 3.4 0.1 0.4 1.1 0.4 1.9 0.1 0.5 0.7 0.3 
31 / 5/ 72 10.8 50.80 13.46 2.9 0.0 0.6 0.1 0.1 3.6 0.1 2.1 1.0 0.6 1.8 0.2 0.3 0.6 0.3 0.6 0.2 0.1 0.5 0.3 
1/ 6172 47.0 101.60 51.30 11.3 0.1 8_3 2Ji 0.5 23.5 0.9 25.9 33.0 5.8 33.0 1.0 21.11 26.3 5.1 40·7 1.0 23.3 27.'il 3.2 
2/ 6172 5.1 30.48 6.86 0.2 0.0 0.1 0_0 0.1 0.10.0 0.20.1 0.1 1.l 0.1 0.2 0.60.2 0.60.00.40.7 0.2 
4/6172 9.5 50.80 12.70 1.2 0.0 0.6 0.2 0.2 0.2 0.0 3.7 1.B 0.5 2.6 0.2 0.6 1.9 n.3 1.2 0.3 0.8 1.7 0.3 
7/6172 9.4 30.48 11.94 1.7 0.0 0.3 0.1 0.1 3.1 0.2 0.7 0.6 0.3 1.8 0.2 0.3 0.7 0.3 0.9 0.1 0.2 0.6 0.3 
9 / 6172 10.8 66.04 11.94 3. . 7 0.0 0.5 0.2 0.1 6.3 0.1 1.6 0.9 0.3 3.3 0_1 0.5 1.1 0.3 2.1 0.2 0.3 0.9 0.3 
13/6172 47.0 71.12 31.24 34.4 0.0 3.7 1.7 0.6 51.2 0.5 24.1 7.1 1.9 39.3 1.1 3.4 8.8 1.426.B 0.9 5.2 14.8 1.3 
~ 
Run-off (mm) losses under slopes and soil management treatment~. -~ 
Rainfall Intensity mmlhr T% 5% 10% 1596 
Date mm Maj(. Mean 234 5 2 3 4 5 2 3 4 5 2 3 4 5 
I II 
16/ 6172 11.4 55.88 15.24 0.9 0.0 0.3 0.1 0.1 4.3 0.3 1.4 0.6 0.3 3.0 0.2 0.5 0.8 0.3 0.3 0.4 0.3 1.1 0.3 
17 / 6 / 72 105.4 142.24 106.43 54.6 0,0 34.2 6.6 1.8 54.6 7.02 31.3 31.4 34.1 54.6 4.1 34 .3 34.2 5.6 54.6 4.0 34.335.5 7.3 
20/ 6/ 72 10.9 30.48 5.84 2.1 0.0 0.5 0.3 0.2 0.3 0.3 0.6 0.5 0.5 3.0 0.2 0.3 0.4 0.3 0.3 0.7 0.1 0.4 0.3 
23/6172 6.9 40.64 8.38 3.0 0.0 0.4 0.1 0.1 2.1 0.0 0.6 0.4 0.2 2.7 0.2 0.3 0.4 0.3 1.8 0.1 0.2 0.6 0.4 
24/ 6172 34.3 60.00 21.0B 13.6 0.0 2.7 0.7 0.4 20.1 0.4 7.1 2.5 O.B 18.2 0.8 3.0 7.0 0.9 23.5 0.6 3.1 7.0 0.9 
2B / 6 / 72 7.6 50.80 8.38 0.6 0.0 0.2 0.0 0.0 1.3 0.0 0.3 0.2 0.1 O.B 0.0 0.3 0.4 0.2 0.7 (),1 D.I 0.6 0.3 
:3 / 7172 15.2 91.44 20.32 5.7 0.0 1.0 0.4 0.2 8.3 0.2 1.3 0.7 0.4 7.1 0.5 1.0 1.3 0.5 7.0 0.2 0.6 0.2 0.6 
417172 8.3 50.80 11.18 3.1 0.0 0.5 0.1 0.0 3.7 0.1 0.7 0.4 0.2 3.7 0 2 0.6 0.8 0.2 3.6 0.1 0.5 1.2 0.3 
1217172 30.5 71.12 35.56 B.O 0.0 1.5 0.5 0.4 21.2 0.3 ;.2 0.8 0.7 11.9 0.7 1.3 1.4 0.7 11.0 0.4 1.0 2.2 0.9 
1717172 8.9 30.48 10.92 0.6 0.0 0.2 0.1 0.1 2.2 O. i 0.3 0.3 0.2 0.9 0.2 D.2 0.1 0.1 1.0 OJ 0.2 0.3 0.3 
7/ 9172 12.7 52.83 14.99 1.7 0.0 0.3 0.2 0.1 3.0 0.3 1.4 0.5 0.9 0.9 0.9 0.5 0.9 0.4 1.4 0.4 0.5 0.4 D.6 
8/ 9/ 72 11.4 40.64 8.38 0.4 0.0 0.0 0.1 0.1 0.5 0.1 0.3 0.2 0.4 0 ,_-6 0.2 0.4 0.3 0.3 0.4 0.3 0.3 0.3 O .~ 
1619172 12.5 50.80 17 .02 0.7 0.0 0.2 0.2 0.1 0.9 0.2 0.4 0.3 0.2 1.2 0.4 0.6 0.4 0.6 0.5 0.3 1.1 0.9 0.7 
19 / 9/ 72 31.8 42.18 B.3 0.0 0.7 0.4 0.2 9.6 0.2 4.5 0.6 6.1 5.0 0.6 0.9 0.6 0.9 1.7 0.5 1.1 0.9 3.2 
21 /9172 30.5 101.60 22.86 9.6 0.0 2.0 0.3 3.7 13.6 0.2 5.0 0.6 12.3 4.7 0.6 4.4 0.8 2.7 11.0 0.5 4.6 0.9 8.5 
25/ 9/ 72 13.3 (30.96 15.24 2.7 0.0 0.3 0.2 0.2 3.6 0.1 1.9 0.4 6.4 3.7 0.5 0.8 0.5 0.6 1.6 0.4 O.B 0.6 1.6 
26 /9/ 72 10.9 25.4 5.08 1.4 0.0 0.1 0.1 0.1 3.6 0.1 0.6 0.3 0.3 3.4 0.2 0.5 0.3 0.3 1.6 0.0 0.4 fl.2 1.0 
3/10172 12.7 30.48 8.38 0.4 0.0 0.4 0.1 0.1 0.9 0.1 0.4 0.4 0.4 0.8 0.3 0.5 0.4 0.4 0.5 0.3 0.4 0.5 O.S 
7/10172 15.8 91.44 20.32 3.7 0.0 0.2 D.4 0.4 0.4 0.4 0.4 0.4 0.4 3.7 0.3 0.5 0.5 0.4 3.4 0.2 0.4 0.5 0.5 
18/ 10/ 72 B.6 50.30 10.16 1.2 0.0 0.3 0.2 0.1 2.9 0.2 0.3 0.3 0.3 3.6 0.2 0.5 0.5 0.4 3.4 0.3 0.4 fl.5 0.5 
Soi l loss (ton/ ha under d ifferent slup'" end soi l n1anagement treatments 
R{} infall Intensity mm! lI r !% 5% TfJ}6 15% 
Date mm Max., Mean 2 3 -1 5 2 3 4 5 2 :1 4 5 ? 3 4 5 
2/ 3/77. 50.8 C.OO 0.00 0.05 0.05 0.G7 0.19 0.000.20 0.19 0.13 0.630.00 0.83 0.50 1.12 0.80 0.801.00 0.64 1. :16 
16/ 3/72 5.1 0.01 0.00 0.01 0.01 0.02 0.01 0.00 0.02 0.02 0.01 0.01 0.00 0.03 0.03 0.03 0.01 0.000.01 0.01 0.01 
5/ 4/ 72 12.7 0.06 0.00 0.04 0.02 0.02 0.08 0.000.08 0.05 0.13 0.11 0.00 0.13 0.11 0.12 0.06 0.00 0.05 0.07 0.05 
7/ 4/ 72 14.0 0.00 0.00 0.00 0.',)0 0.00 0.00 0 .00 0 .00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 o.no 0.00 0.00 0.00 
14(4(72 ZJ.5 G.(\(l (l.00 0.00 O.O(l 0.00 0.00 O.G\) a.oll 1l.00 0.00 0.000.00 0.00 0.00 0.00 0.00 0.000.00 0.00 0.00 
20 / 4/ 72 13.3 0.06 0.00 0.05 0.02 0.05 0.11 0.040.12 0.16 0.07 0.08 0.03 0.14 0.19 0.09 0.09 0.06 0.14 0.11 0.15 
23/ 4172 22.2 O.G2 0.00 0.17 0.00 0.00 0.01 0.000.03 0.02 0.03 0.040.00 0.D2 0,00 0.01 0.03 0.00 0.Q1 0.06 0.04 
30 / 4172 10.8 81.28 14.22 0.04 0.00 0.02 0.02 0.D1 0.01 O.QO 0.13 0.09 0.Q8 0.060.00 0.03 0.07 0.03 0.03 0.000.04 0.05 O.OB 
4/ 5/ 72 20.0 50.80 23.11 0.06 0.00 0.05 0.03 0.02 0.09 0.040.20 0.13 0.26 0.060.00 0.12 0.15 0.09 0.04 0.00 0,05 0.04 0.12 
815/72 ~3.3 38.58 7.62 0.04 0.00 0.03 0.00 0.00 0.00 0.000.06 0.06 0.10 0.020.00 0.03 0.04 0.00 0.04 0.060.05 0.00 0.12 
11 / 5/ 72 12.7 30.48 8.38 0.03 0.00 0.01 0.02 0.00 0.02 0.00 0.03 0.04 0.10 0.02 0.00 0.00 0.00 0.02 0.00 0.00 0.00 0.00 0.01 
14/6/ 72 13.3 40.64 15.74 0.04 0.00 0.10 0.00 0.00 0.22 0.00 0.06 0.02 0.05 0.160.00 0.00 0.14 0.02 0.11 0.00 0.00 0.09 G.TO 
27/ 5172 36.57 19.30 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 
28/ 5/ 72 61.0 91.44 33.02 0.57 0.00 0.03 0.04 0.00 1.52 0.000.33 0.03 O.OS 1.670.00 0.07 0.50 0.00 0.01 0.000.50 0.40 0.00 
29 / 5172 10.80 50.80 12.95 0.03 0.00 0.00 0.00 0.00 0.11 0.00 0.02 0.00 0.01 0.12 0.00 0.00 0.03 0.01 1.73 0.00 0.D2 0.02 0.00 
31 / 5172 10.8 50.80 12.95 O.M 0.00 0.00 0.00 0.00 0.16 0.000.03 0.00 0.00 0.120.00 0.00 0.00 0.00 0.18 0.00 0.01 0.00 0.00 
116172 47.0 101.60 51.30 0.39 <l.OO 0.06 0.Q2. 0.00 2.75 0.00 0.24 0.14 (HIS 3.85 0.02 0.94 0.73 0.02 13.56 0.003.552.080.00 
2/6172 5.1 20.32 4.95 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.70 0.00 0.00 0.09 0.00 0.94 0.00 0.19 0.15 0.00 
4/ 6172 9.5 40.S4 11.93 0.07 0.00 0.02 0.00 0.00 1.34 0.00 0.19 0.03 0.00 1.79 0.00 0.08 0.21 0.00 2.49 0.000.21 0.300.00 
7 / 6172 9.4 0.04 0.00 ' 0.00 0.00 0.00 0.67 0.00 0.06 0.02 0.00 0.79 0.00 0.00 0.05 0.00 1.34 0.000.030.030.00 
9 / 6172 10.8 54.86 9.91 0.10 0.00 0.01 0.00 0.00 1.20 0.00 0.04 0.03 0.00 1.30 0.00 0.02 0.03 0.00 3.20 0.001.00 0.57 0.00 
13/ 6172 47.0 71 .12 31.24 0.6<' 0.00 0.10 <l.OS 0.00 5.08 0.00 1l.29 0.13 0.05 3.95 0.00 0.03 o.:n 0.52 15.0 0.00 1.00 0.580.00 
16 /6/ 72 11.4 50.80 14.48 0.03 0.00 0.01 0.00 0.00 0.92 0.00 0.07 0.01 0.00 0.84 0.00 0.00 0.03 0.00 3.83 0.00 0.00 0.040.00 
17 IS 172 105.4 121.92 97.53 0.80 0.00 0.1 B 0.03 0.00 4.27 0.01 0.27 0.22 0.10 4.27 0.09 2.58 1.43 0.03 29.80 0.025.481.550 .01 
20/ 6172 10.9 30.48 5.84 0.04 0.00 0.00 0.00 0.00 0.18 0.00 0.02 0.02 0.00 2,()2 0.00 0.00 2.0? 0.(,0 0.68 0.00 0.00 0.00 0.00 
23/ 6172 6.9 ~.48 5.08 0.15 0.00 0.00 o.M 0.00 0.71 0.00 0.01 0.00 0.00 0.83 0.00 0.00 0.00 0.00 2.35 0.000.050.040.00 
.t.:.;..;  
Soil loss (Ion / hal un tl~, cJiffp'Pflt s lopllS d ill] soil m,m ail'lrTl,," 1 tr"<Jlm "nts. ~ 
r:ilinf,~ 11 Intensi t y Iml1l / hr) 1% 5,}{, 10% 15% 
Date mm Max. Mean 2 3 4 5 2 3 4 5 2 3 4 5 2 3 4 5 
2[;16172 34.3 fll.2fl 19.05 0.24 0.00 O.Of, 0.00 0.00 3.73 0.00 0. 16 0.03 0.00 8.90 0.00 0.09 0.21 0.00 7.30 0.00 0.89 1.10 0.00 
2B16! 72 7.6 40.72 8.3B 0.03 0.00 0 .:)1 0.00 0.00 0.~2 0.00 0.00 0.00 0.00 0 .56 0 .00 0 .00 o.on o.no 1.03 0.00 0.00 0.02 0.00 
317172 14 .6 101.60 19.05 0.19 0.00 0.01 0.00 0.00 2.02 0.00 0.04 0.02 0.00 4.39 0.00 0 .04 0.Q7 0 .')0 5.10 0.00 0.03 0.17 0.00 
41717'1 7.6 54.86 11.' 8 0. 11 0.00 0.00 0 .07 0.00 1.£11 0.00 0.01 0.00 0.00 2.56 0.00 0.01 0.05 0.00 5.00 0.00 0.06 O.OB 0.00 
12/7 /72 29 .8 55 .88 34.04 0.12 0.00 0.00 0.00 0.00 3.22 0.00 0.00 0.00 0.00 5.11 0.00 0.02 0.02 0 .00 4.88 0.00 0.01 0.00 0.00 
1717172 B.9 26 .41 10.61 0.01 0 .00 0 .00 0 .00 0 .00 0.86 0.00 0.00 0.00 O.on 0.54 0.00 0.,)0 0.00 o.no (UG 0.0r. 0.00 0.00 0.00 
7/ 9172 12.7 b2.83 14.99 0.12 0.00 0.00 0 .00 0.06 0.li9 0.00 0.'.)1 0.00 0 .01 0 .24 0.00 0.00 0.00 0.01 0.39 0 .00 0.06 0.00 0.01 
8/ 9172 11.4 30.48 7.37 0.00 0.00 0 .00 0.00 0 .00 0 .01 0.00 0.00 0.00 0 .00 O.rn 0 .00 0.00 0 .00 0.00 0.00 0.00 0 .00 0.00 0.00 
16 / 9172 12.5 50.80 15.75 0.00 0.00 0.00 0.00 0.00 0.01 0.00 0.00 0.00 0.00 0.00 0 .00 0 .00 0 .00 0.00 0 .00 0 .00 0.00 0.00 0.00 
19/9/72 31.8 0.35 0.00 0.00 0.00 0.00 2.56 0.00 0.\)8 0.00 0 .29 2.JIl 0.00 0.00 n.on 0 .05 0 .55 0.00 0 .00 0.91 0.01 
21 / 9172 30.5 101 .60 20.83 0.26 0.00 0.05 0 .00 0 .20 2.56 0.00 0.29 0.00 0.77 3.86 0.00 0 .56 0.00 0.88 6 .03 0.00 1.22 0.05 2.90 
25/ 9172 13.3 50.80 14.99 0.15 0.00 O.CO 0.00 0.00 1.52 0.00 0.02 0.00 0.04 2.47 0.00 0 .01 0.00 0.00 1.89 0 .06 0.0'3 0.01 0 .85 
26/9 / 72 10.9 36 .'-'8 9 .91 0.00 0.')0 0.00 0.00 0.00 1.58 0.00 0.00 0.00 0.00 1.76 0.00 0.00 0.00 0.00 1.79 0.00 0.00 0.00 0.64 
3110172 30.48 7.37 0.00 0.00 0.00 o.no 0.00 0.34 0.00 0.00 0.00 0.00 0.27 0.00 0.00 0.00 0.00 0.14 0.00 0.00 0.00 0.00 
7 / 10/ 72 15.8 26.42 18.80 0.01 0.00 0.00 0.00 0.00 0.32 0.00 0.00 0.00 0.00 0.24 0.00 0.00 0.00 0.00 0.17 0.00 0.00 0.00 0.00 
18 / 10/ 72 29.5 SO.80 9.91 0.11 0.00 0 .00 0.00 0.00 1.46 0.00 0.00 0.00 0.00 2.1 2 0.00 0.00 0.00 0 .00 4.15 0.00 0.00 0.00 0.00 
Effec t of contour Ip.ngth on Sod dnd water lo ss under nlCl 17e·cowp ea rotiltion 
Rainfall Intensity fmm/hr) 
Date 12.S m 37.5 m 
mm RUIl·off (rMl) Soil luss (tuns/ha) Run-off (mm) Soil loss (tonslha) 
Max. Mean 10.2% 19. 2"~ 10.2% 19.2% 9.3% 13.4% 9.4% 13..4~ 
2/ 3/ 72 50.3 13.71 7.38 2.78 0.24 22.53 2.46 1.41 0.23 
16/ 3/ 72 5,1 0.09 0.09 0.13 0.01 0.05 0,09 0.02 0.01 
5 / 4172 12.7 1.01 1.01 0.39 0.10 0.31 0.27 0.16 0.04 
7/ 4/ 72 14.0 1.05 0.91 D.nn 0.00 0.31 0.24 0.00 0.00 
14/ 4/ 72 23.5 0.91 1,00 0.00 0.00 0.31 0.18 0.00 0.00 
20/ 4/ 72 13.3 1.82 1.66 0.91 0.82 0.67 0.49 1.00 0.88 
23/ 4/ 72 22.2 1.29 1.00 0.28 0.04 0.30 0.12 0.04 0.02 
30/4172 10.8 81.28 14.22 1.45 0.73 0.42 0.09 0.39 0.30 0.08 0.04 
4/5/72 20.0 50.80 23.11 1.20 1.B!) 0.42 0.12 0.52 1.85 0.09 0.22 
8-9 / 5/72 13.3 36.58 7.62 2.49 1.45 0.36 0.06 0.62 0.62 0.00 0.03 
11/5172 12.7 30.48 8.38 1.66 0.92 0.19 0.00 0.19 0.00 0.00 0.00 
14/5172 13.3 40.64 15.74 2.77 8.95 0.18 0.12 0.89 0.86 0.05 0.04 
27/5/72 36.57 19.30 0.56 0.46 0.00 0.00 0.19 0.19 0.00 0.00 
28/5/72 61.0 91.44 33.02 32.73 26.58 1.42 0.45 6.22 7.01 0.11 0.06 
29/5172 10.8 50.80 12.95 1.75 1.29 0.23 0.00 0.49 0.39 0.12 0.13 
1/6/72 47.0 101 .60 51.30 49.55 36.69 5.24 1.10 53.13 53.13 2.91 1.34 
2/6/72 5.1 20.32 4.95 1.18 1.64 0.00 0.07 0.45 0.54 0.21 0.30 
4/6/72 9.5 40.64 11.93 3.09 2.36 0.53 0.24 1.94 1.39 0.79 0.45 
7/6/72 9.4 1.82 1.09 0.07 0.06 0,54 0.39 0.13 0.07 
9/6/ 72 10.8 54.86 9.91 2.54 1.27 0.13 0.06 0.48 0.78 0.07 0.05 
9 
Effec t of con~OLlr le.19th on soil and water 1055 under maize-co\'t,)ca .otation ~- 
RDinfa/l If/tensily (mmlhrl 12.51/1 37.5 I)J 
Date m'" Rlln-off (mill) 
-- Soil Ius !; (tulls/hal Run-off (mm) Soil foss (tons/ha) 
Max. Mean 10.n 19.2'}h 10.2% 19.2% 9.3% 13.4% 9,4% 13.4% 
13/ 6/72 47.0 71.12 31.24 8.96 22.43 0.64 1.73 7.21 1 A.OO 0.86 0.31 
16/ 6172 11.4 50.80 14.48 U;4 2.11' 0.04 0.06 O.Bl (1. !l4 0.05 0.05 
17/ 6/ 72 10fi.4 121.92 97.53, 68.51 68.51 5.11 1.09 22.26 22.35 1.33 0.98 
20/ f: / 72 10.9 30.48 5.84 1.0~ 1.27 0.14 '0.11 0.24 0.36 0.03 0.00 
23/ 6 / 72 6.9 30.4R 5.0R 1.09 1.45 0.12 0.10 0.31 0.54 0.04 0.07 
25 / 6172 34.3 81.28 19.0Fi 12.31 11.34 6.70 0.53 6.92 8.73 1.20 0.24 
28/ 6/72 7.6 45.72 8.3R 1.10 1.20 0.06 0.05 0.49 0.88 0.07 0.02 
3/7/72 14.6 101.60 19.05 3.69 4.28 0.28 0.35 1.58 2.18 0.22 0.13 
417172 7.6 54.86 11.18 1.82 2.36 0.15 0.19 0.Q5 1.09 0.13 0.10 
12/7/72 29.8 55.88 34.04 4.54 4.73 0.15 0.Q7 1.70 2.39 0.10 0.03 
17/7/ 72 8 .9 26.41 10.67 0.55 0.36 0.00 0.00 0.12 0.27 0.00 0.00 
719/ 72 12.7 52.83 14.99 0.82 0.91 0.01 0.12 0.27 0.36 0.00 0.02 
8/9/12 11.4 20.48 7.37 0.73 0.55 0.00 0.00 0.18 0.21 0.00 0.00 
16/9/72 12.5 50.80 15.75 1.00 0.90 0.00 0.00 0.31 0.27 0.00 0.00 
19/ 9172 31.5 2.32 3.0~ 0.29 0.1 0 O. 73 0.55 0.25 0.01 
21 / 9/ 72 30.5 101.60 20.83 7.28 B.36 2.30 2.78 4.89 4.10 0.99 1.10 
25/9172 13.3 50.80 14.99 2.46 3.46 0.07 0.15 0.73 0.79 0.05 0.01 
26/9/ 72 10.9 36.58 9.91 1.27 1.r;4 0 .01 0.00 0.70 0.55 O.O~ 0.00 
3/10/72 30.48 7.37 0.91 0.91 0.00 {'.OO 0.36 0.30 0.00 0.00 
7/ 10/72 15.8 26.42 18.80 1.27 0.93 0.01 0.01 0.67 0.31 0.00 0.00 
18/10/72 29.5 50.80 9.91 0.73 0.91 0.00 0.00 0.30 0.30 0.00 0.00 
APPENDIX lb Run-off and soil loss records for individual rain storm during 1973 
Run-off (mm I losses under different slopes and soil management treatments. 
R{linfall {ntensity mm/ hr I 7% 5% 10% 15% 
Dare mm Max. Mean 234 5 2 3 4 5 2 3 4 5 2 3 4 5 
1712173 8.9 50.80 11.68 1.5 0.0 0.2 0.0 0_1 2.2 0.1 0.1 0.0 0.0 1.3 0.0 0.1 0.0 0.0 0.2 0.1 0.1 0.0 0.1 
14/3/73 21.6 30.48 13.20 1.9 0.0 0.3 0.3 0.3 3.5 0.2 0.4 0.1 0.4 2.2 0.4 0.6 0.5 0.4 0.5 0.3 0.5 0.5 0.6 
2213173 8.4 15.24 5.08 1.9 0.0 0.3 0.3 0.2 2.5 0.1 0.4 0.2 0.3 2.2 0.5 0.7 0.6 0.5 0.5 0.5 0.6 0.1 0.8 
2513/13 10.4 50.80 10.16 3.6 0.0 0.5 0.4 0.3 3.6 0.1 0.6 0.2 0.5 3.7 0.6 0.9 0.1 0.6 0.1 O.S 0.1 O.B 1.0 
4/4173 34.0 71.12 35.56 3.7 0.0 0.6 0.6 0.5 9.0 0.6 0.9 0.4 0.5 4.4 1.1 1.3 1.1 1.1 1.5 0.9 1.4 1.5 1.5 
21-23/4/73 48.8 172.72 49.78 17.6 0.0 9.6 0.6 7.7 7.7 0.6 17.2 0.9 15.2 15.6 1.5 6.5 1.5 19.5 14.9 1.0 7.7 1.7 8.4 
25/4/73 4.1 32.51 5.33 0.4 0.0 0.1 0.0 0.0 1.0 0.0 0.7 0.0 0.5 0.8 0.0 0.2 0.1 0.1 0.3 0.1 0.3 0.1 0.3 
27/4173 24.5 91.44 32.27 5.7 0.0 6.9 0.2 5.5 9.6 0.3 13.4 0.5 13.6 9.6 0.6 5.1 0.6 7.7 9.0 0.5 6.7 0.7 6.9 
6/5173 16.5 40_64 21.83 6.3 0.0 3.2 0.2 0.9 6.3 0.2 5.7 0.4 0.5 7.0 0.4 1.2 0.4 1.S 5.7 0.5 3.2 0.6 2.0 
24/5/73 17.0 60_96 22.61 3.6 0.0 0.7 0.3 0.3 8.3 0.2 6.5 0.4 7.7 5.0 0.5 0.7 0.5 0.1 2.8 0.3 1.8 0.6 2.0 
31/5173 13.5 91.44 17.78 5.7 0.0 1.3 0.2 0.1 6.3 0.1 6.9 0.1 1.1 6.3 0.4 0.1 0.4 0.5 6.3 0.4 2.3 0.5 0.5 
5/6173 19.1 71.12 20.32 7.7 0.0 0.9 0.2 0.1 8.6 0.1 7.7 0.2 2.1 5.1 0.4 0.9 0.4 0.6 9.6 0.3 2.6 0.5 0.8 
8/6173 7.6 40.64 10.16 0.7 0.0 0.2 0.1 0.1 0.2 0.2 1.2 0.2 0.3 0.9 0.2 0.2 0.1 0.2 0.3 0.1 0.1 0.2 0.3 
10/6/73 44.2 27.1 0.0 3.7 0.6 0.4 30.1 0.5 13.6 0.8 12.8 24.2 0.9 5.7 0.9 1.7 33.4 0.8 14.8 1.0 2.2 
13/6173 22.9 71.12 27.94 8.3 0.0 2.8 0.2 0.0 7.0 0.2 8.0 0.3 6.9 10.3 0.4 1.5 0.4 0.6 10.3 0.3 6.9 0.4 0.6 
21/6173 6.9 30.48 9.14 1.1 0.0 0.1 0.1 0.1 0.9 0.1 0.2 0.1 0.1 0.6 0.1 0.2 0.2 0.1 0.2 0.1 0.1 0.1 0.2 
23/6/73 39.4 50.BO 25.40 22.2 0.0 1.2 0.6 0.1 26.1 0.4 14.0 0.2 1.4 22.8 0.8 2.3 0.9 1.1 22.8 0.7 4.9 1.0 1.3 
25/6173 5.3 30.48 7.11 1.9 0.0 0.2 0.2 0.10.20.10.40.1 0.1 1.8 0.1 0.2 0.1 0.1 0.1 0.1 0.3 0.1 0.2 
117173 19.8 20.32 11.94 4.1 0.0 1.8 1.0 0.3 16.2 0.3 6.9 1.1 0.8 9.6 0.1 1.6 0.7 1.1 15.6 0.8 4.1 0.8 1.2 
2/7173 25.4 55.80 23.62 16.2 0.0 2.1 0.4 0.2 20.2 0.1 7.7 0.1 0.7 10.3 0.6 1.4 0.5 0.7 16.9 0.4 5.7 0.5 0.6 
517/73 14.5 60.80 13.46 7.0 0.0 0.5 0.2 0.1 4.4 0.1 2.1 0.3 0.2 5.7 0.3 0.5 0.3 0.3 2.8 0.2 1.0 0.3 0.5 
S1 
RlIn-off /mml losses CInder different slopes lind soil managallent trealmentS. -~ 
Hi/inti/II In!ensity mml hr~ 196 5% rew, 15% 
Dare mm Max. Mean 2 3 4 5 2 3 4 5 '} 3 4 5 'l 3 4 5 
1217/ 73 30.5 50.80 28.19 16.9 0.0 1.3 0.4 0.2 16.9 0.2 6.3 0.5 O.B '0.6 0.5 0.9 0.5 0.6 11.9 0.5 0.7 0.6 0.7 
2317173 50.8 111.76 65.79 36.7 0.0 6.1 0.7 0.3 38.7 0.223.9 0 .7 0.7 40.0 0.9 11.2 1.0 1.1 33.4 0.7 12.0 1.0 0.8 
27 / 7/73 11.4 30.48 10.16 2.2 0,0 0.1 0.2 0.1 2.1 0.2 0.5 0.2 0.2 0.5 0.1 0.3 0.3 0.3 0.3 0.1 0.3 0.3 0.3 
30/7173 20.8 30.46 15.24 9.2 0.0 0.5 0.5 0.3 9.3 0.2 0.8 0.3 0.3 5.0 0.4 0.3 0.5 0.5 3.7 0.5 0.6 0.7 0.6 
1/B173 9.4 20.32 9.91 3.0 0.0 0.2 0.2 0.1 5.0 0.1 0.4 0.1 0.3 3.1 0.2 0.4 0.4 0.2 1.8 0.2 0.3 0.3 0.3 
5/8/73 1 31 .B 81.28 45.72 56.0 0.0 7.7 2.0 1.1 56.2 1.3 8.6 2.3 4.5 55.2 6.1 7.7 5.7 6.3 55.2 3.2 4.7 3.8 9.0 
8/8/13 63.0 101.60 72.64 44.0 0.1) 2.2 0.8 0.5 45.3 0.7 4.9 1.0 2.4 46.6 1.6 4.9 2.0 3.2 55.2 2.B 6.9 1.7 0.4 
319173 26.20 60.96 21.59 S.O 0.0 1.1 O.B 0.4 5.7 0.5 1.8 0.7 1.0 5.0 U 2'() 1.4 1.7 3.5 1.1 1.7 1.4 3.4 
lO/ 9173 50.80 91.44 50.80 24.8 0.0 1.4 O.B 6.5 36.7 0.5 7.3 0.815.6 27.5 1.4 4.5 1.5 3.6 23.5 1.4 8.8 1.0 15.6 
12/9173 37.10 40.64 30.48 16.9 0.0 2.0 0.4 10.8 21.5 0.311.2 0.4 9.S 14.9 0.8 3.0 0.8 3.316.9 0.611.2 0.8 11.6 
16·17.19173 6.40 50.80 8.38 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 
23/9173 27.9 162.40 33.02 13.6 0.0 1.4 0.4 0.9 15.6 0.2 5.0 0.4 2.3 20.1 0.6 2.7 0.9 2.1 15.6 0.6 6.5 0,9 7.7 
Run~ff (mm) losses under diHereot Slopes and soil manaQement trea1ments. 
Rainfall Inrensiry mml hr 7% 596 1096 1596 
Date mm MaK. Mean 2 3 4 5 2 3 4 5 2 3 4 5 2 3 4 5 
24/ 9173 34.3 81.28 30.48 28.8 0.0 1.6 0.6 0.4 24.2 0.3 10.4 0.5 B.O 30.8 0.8 8.4 0.8 0.4 17.2 0.5 B.4 0.7 10.0 
2919173 19.56 60.95 23.62 4.5 0.0 1.0 0.4 0.4 10.3 0.3 5.7 0.5 4.9 14.3 1.0 3.3 0.7 3.2 16.2 O.B 6.9 1.1 7.7 
2919173 25.9 76.20 31.00 18.9 0.0 3.1 0.5 1.1 ZQ.2 0.3 11.6 0.5 1'.6 20.2 0.7 5.7 0.8 6.7 23.5 0.7 10.8 0,8 14.4 
3 /10173 ~ 1 ,2 30.48 11,94 6.5 0.0 0.4 0.2 0.2 7.0 0.3 0.6 0.1 0:<6 5.0 0.1 0.4 0.2 0.5 6.3 0.1 0.1 0.5 1.9 
13/ 10173 lR.2 60.96 23.62 6.7 0.0 0.1 0.3 0.2 7.7 0.4 1.9 0.4 0.8 6.3 0.7 1.2 0.6 1.0 B.3 0.5 1.3 0.7 1.1 
18/ 10173 5.8 46.74 7.62 0.7 0.0 0.0 0.1 0.1 1.0 0.1 0.2 0.2 0.1 1.5 0.1 0.1 0.1 0.1 1,1 0.1 0.1 0.2 0.1 
20·21 110 173 15.0 40.64 13.46 6.3 0.0 0.2 n.Z 0.1 6JJ 0.1 13.5 0.3 0.2 4.1 0.2 0.4 0.4 0.4 0.3 0.2 0.5 0.5 0.4 
23/10n3 37.0 76.20 2B.70 14.6 0.0 0.6 0.5 0.1 17.6 0.2 2.7 0.6 2.7 10.9 0.5 1.5 0.7 2.1 16.2 0.3 3.3 0.8 14.8 
25/10173 15.4 30.48 15.24 5.7 0.0 0.4 0.2 0.8 5.7 0.2 0.9 0.3 0.8 6.3 0.2 0.5 0.3 0.9 6.3 0.1 1.1 O.~ 2.2 
27110/73 15.8 81.28 20.83 4.(\ 0.0 0.5 0.2 0.1 11.6 0.1 1.9 0.3 2.8 12.9 0.2 0.8 0.4 1.9 11.6 0.2 3.3 0.4 5.3 
30/ 10173 29.8 80.96 20.32 12.3 0.0 0.8 0.4 0.1 5.0 0.2 3.3 0.5 3.5 13.3 0.6 I.S 0.6 3.6 18.9 0.3 6.5 0.6 9.2 
Soil loss (ton/ ha) under different slopes and soi I management treatments. 
Rainfall Intensity ( mml hr J 1% 5% 10% 15% 
Date mm Max. Mean 2 3 4 5 2 3 4 5 2 3 4 5 2 3 4 5 
1712/73 8.9 50.80 11.68 0.00 0.00 0.00 0.00 0.00 0.68 0.00 0.00 0.00 0.00 0.82 0.00 0.00 0.00. 0.00 0.00 0.00 0.00 0.00 0.00 
14/ 3/73 21.6 24.38 13.20. 0.00 0.00 0.00 0.00 0.00 1.00 0.00 0.00 0.00 0.00 0.73 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 
22/ 3/73 B.4 14.22 3.3:) 0..00 0.00 0.00 0.00 0.00 0.00 0.00. 0.00 0.00 0.00 O.no 0.00 o.[)() 0.00 0.00 0.00 0.00 0.00 0.00 0.00 
25/ 3173 10.4 30.4B 9.65 0.00 0.00 0.00 0.00 0.00 0.93 0.00 0.00 0.00 0.00 1.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 
14/ 4173 34.0. 71.12 34.79 0.46 0.00 0.00 0.00 0.00 2.36 0.00 0.00 0.00 0.00 2.01 0.00 0.00 0.00 0.00 0.96 0.00 0.00 0.00 0.00 
21-23/ 4173 48.0 172.72 49.78 0.41 0.00 0 .3:) 0.01 0.24 1.60 0,02 0.52 0.03 0.65 8.36 0.00 0.92 0.00 1.71 3.62 0.00 1.94 0.10 1.22 
25/4/73 4.1 26.42 5.33 0.03 0.00 0.00 0.00 0.00 0.60 0.00 0.00 0.00 0.00 0.73 0.00 0.00 0.00 0.00 0.32 0.00 0.14 0.00 0.00 
27 / 4173 24.6 71.12 31.50 0.19 0.00 0.15 0.00 0,13 1.83 0.00 0.59 0.00 2.77 7.62 0.00 0.97 0.01 1.14 B.34 0.00 4.15 0.00 2.93 
6 15173 16.5 40.64 20.83 0.26 0.00 0.03 0.00 0.19 2.13 0.00 0,17 0.00 0.47 4.62 0.00 0.17 0.00 0.26 3,91 0.00 1.77 0.00 2.02 
2415173 17.0 60.96 16.51 0.19 0.00 0.01 0.00 0.01 1.62 0.00 0.23 0.00 0.68 2.46 0.00 0.06 0.00 0.11 1.79 0.00 0.38 0.00 0.37 
31 / 5/73 13.5 91.44 17.53 0.24 0.00 0.07 0.00 0.00 2.00 0.00 0.23 0.00 0.22 5.66 0.00 0.12 0.01 0.03 4.99 0.00 0.65 0.00 0.11 
5/6173 19.1 71.12 19.81 0.18 0.00 0.02 0.00 0.00 3.92 0.00 0.21 0.00 0.15 6.00 0.00 0.09 0.00 0.00 6.76 0.00 0.88 0.00 0.03 
8/ 6/73 7.6 30..48 9.91 0.00 0.00 0.00 0.00 0.00 1.19 0.00 0.00 0.00 0.00 0.58 0.00 0.00 0.00 0.00 0.20 0.00 0.00 0.00 0.00 
10./6/73 44.2 0.24 0.00 0.04 0.00 0.00 3.76 0.00 2.Bl 0.00 0.36 12.66 0.00 0.41 0.00 0.00 17.11 0.00 4.07 0.00 0.04 
13/6/73 22.9 60.96 24.89 0.17 0.00 0.06 0.00 0.00 6.64 0.00 0.48 0.01 0.19 9.23 0.00 0.13 0.00 0.00 8.77 0.00 2.23 0.00 0.01 
21/6173 6.9 30.48 8.38 0.03 0.00 0.00 0.00 0.00 0.86 0.00 0,02 0.00 0.00 0.60 0.00 0.00 0.00 0.00 0.13 0.00 0.00 0.00 0.00 
23/6n3 39.4 40.64 15.00 0.45 0.00 0.04 0.00 0.00 6.05 0.00 0.55 0.02 0.00 7.08 0.01 0.06 0.00 0.00 B.71 0.00 1.65 0.00 0.05 
25/ 6173 5.3 20.32 13.21 0.03 0.00 0.00 0.00 0.00 2.41 0.00 0.01 0.00 0.01 0.92 0.00 0.00 0.00 0.00 0.69 0.00 0.00 0.00 0.01 
117173 19.8 20.32 13.21 0.21 0.00 0.11 0.00 0..00 7.58 0.00 0.49 0.11 0.00 6.25 0.01 0.11 0.00 0.01 6.g1 0.00 1.38 0 .00 0.00 
217173 25.4 50.80 23.11 0.22 0.00 0.04 0.00 0.00 9.84 0.00 0.66 0.01 0.01 5.42 0.00 0.02 0.00 0.00 5.48 0.00 0.99 0.00 0.00 
517173 U.S 50.80 12.45 0.17 0.00 0.00 0..00 0.00 3.Bl 0.00 0.14 0.03 0.00 2.39 0.00 0.02 0.00 0.00 1.81 0.00 0.15 0.00 0.00 
1217173 30.5 40.64 28.19 0.27 0.00 0.02 0.00 0.00 6.46 0.00 0.34 0.01 0.00 3.85 0.00 0.09 0.00 0.00 2.64 0.00 0.08 0.00 0.00 
2317173 50..8 111.76 48.26 0.45 0.00 0.07 0.00 0.00 3.62 0.00 0.37 0.00 0.00 7.34 0.00 0.12 0.00 0.00 5.91 0.00 1.80 0.00 0.00 
2717173 11.4 24.38 9.91 om O~ O~ om om 1~ om om O~ O~ 0.20 0.00 0.00 0.00 0.00 0.00 0.07 0.01 0.00 0.00 
30nn3 20.8 30.48 13.97 0.06 0.00 0.00 0.00 0.00 2.74 0.00 0.01 0.00 0.00 2.~ 0.00 0.01 0.00 0.00 1.98 0.00 0.00 0.00 0.00 
t:l 
'" 
Soil loss (ton/ha I under different slopes and soil manaoement treatments. ~ 
Rili/lfalf IntensifY (mm/hr J 1% 5% 109(, 15% 
Date ml,' Max. Mean 2 3 4 5 2 3 4 5 2 3 4 5 2 3 4 5 
1/8173 9.4 20.32 8.81 0.13 0.00 0.00 0.00 0.00 1.37 0,00 0.00 0.00 0.00 1.33 0.00 0.00 0.00 0.00 0.36 0.00 0.00 0.00 0.00 
5 / 8/73 181.8 50.80 29.71 2.12 0.00 0.15 0.00 0.00 3.53 0.00 0.27 0.01 0.03 34.01 0.02 0.38 0.01 0.02 30.51 0.01 0.47 0.01 0.37 
8/8173 63.0 121.92 69.34 0.95 0.00 0.15 0.00 0.00 2.61 0.00 0.23 0.00 0.02 19.64 0.01 0.39 0.01 0.02 33.34 1.87 0.88 0.00 0.46 
3 / 9/73 26.2 50.80 21.59 0,23 0.00 0.00 0.00 0.01 1.14 0.00 0.03 0.00 0.01 0.97 0.01 0.01 0.01 0.04 1.96 0,01 0.1 8 0.01 0.35 
10/9/73 50.B 91.44 49.53 0.21 0.00 0.10 0.00 0.12 7.46 0.01 0.47 0.00 0.S7 11.45 0.01 0.59 0.01 0.34 7.97 0.01 1.76 0.00 6.90 
12/9/73 37.1 40.64 28.19 0.28 0.00 0.09 0.00 0.01 5.32 0.01 0.55 0.00 0.72 B.62 0.00 0.25 0.01 0.19 10.90 0.00 2.85 0.00 7.10 
16·17/ 9/73 6.4 40.64 7.64 0.00 0.00 0.00 0.00 0.00 1.95 0.00 0.00 0.00 0.00 2.42 0.09 0.00 0.00 0.00 1.77 0.00 0.13 0.00 0.15 
23/9/73 27.9 121.92 33.02 0.26 0.00 0.03 0.00 0.02 3.17 0.00 0.29 0.01 0.16 11.40 0.00+ 0.33 0.01 0.21 8.04 0.01 2.64 0.00 6.97 
24/9173 34.3 20.32 5.B4 0.42 0.00 0.04 0.00 0.01 8.18 0.00 0.42 0.00 0.42 7.89 0.00 0.90 0.00 0.41 6.42 0.00 2.44 0.00 2.70 
27/9173 66.0 81.28 28.70 0.34 0.00 0.01 0.00 0.01 10.48 0.00 0.37 0.00 0.41 B.l1 0.01 0.13 0.00 0.32 9.31 0.00 1.83 0.00 3.77 
29 / 9/73 25.9 60.96 27.99 0.36 0.00 0.01 0.00 0.00 6.76 0.00 0.15 0.00 0.42 6.39 0.00 0.40 0.00 0.31 8.42 0.00 2.63 0.00 3.35 
3/ 10/73 11.2 30.48 11.1!'l 0.35 0.00 0.01 0.00 0.01 3.97 0.00 0.01 0.00 0.02 3.09 0.00 0.02 0.00 0.01 2.56 0.00 0.13 0.00 0.37 
1 3/10/73 18.2 71.12 22.35 0.07 0.00 0.00 0.00 0.01 3.51 0.01 0.02 0.00 0.15 2.69 0.00 0.02 0.00 0.14 1.51 0.00 0.11 0.00 0.02 
1 B/ l0/73 5.3 40.64 6.B6 0.00 0.00 0.00 0.00 0.00 1.19 0.00 0.00 0.00 0.00 O.SO 0.00 0.00 0.00 0.00 0.34 0.00 0.00 0.00 0.00 
2(}-21 110173 15.0 40.64 12.95 0.10 0.00 0.01 0.00 0.00 1 .B2 0.00 0.14 0.00 0.00 1.23 0.00 0.03 0.00 0.02 0.39 0.00 0.01 0.00 0.02 
23/10/73 37 tJ 71.12 26.42 0.28 0.01 0.00 0.01 0.00 4.34 0.00 0.04 0.01 0.27 4.97 0.00 0.02 0.00 0.03 4.15 0.00 0.44 0.01 0.94 
25/ 10173 15.4 30.48 14.99 0.42 0.00 0.01 0.00 0.06 5.10 0.00 am 0.00 0.D2 2.56 0.00 0.1)1 0.00 0.02 0.76 O.on 0.02 0.00 0.26 
27/10173 15.B 91.44 19.81 0.14 0.00 0.01 0.00 0,07 3.75 0.00 O.OB 0.01 0.71 3.05 0.00 0.03 0.03 0.22 4.13 0.00 0.58 0.00 0.88 
30/10/73 29.5 81.28 18.29 0.22 0.00 0.01 0.00 0.00 7.7 0.00 0.24 0.01 0.10 4.54 0.00 O.O~l 0.00 1) .23 0.31 0.00 1.31 0,00 1.65 
Effect of contour length on soil and .... ater loss under maize-co .... pea rotation 
Rainfall Intensity (mm lhrj 12.5 m 37.5 m 
Date mm Run-off (mm) Soil loss (tons!ha} Run-off (mm} Soil loss ( tonslho/ 
Max. Mean 10,2% 19.2% 10.2% 19.2% 9.3% 13,4% 9,3% 13.4% 
1712173 8.9 50.80 11.68 0.18 0.09 0.00 0.00 0.03 0.09 0.00 0.00 
14/ 3/73 21.6 24.38 13.20 0.92 0.92 0.00 0.00 0.31 0.25 0.00 0.00 
22/ 3173 8.4 14.22 3.30 1.11 1.11 0.00 0.00 0.31 0.34 0.00 0.00 
25/ 3173 10.4 30.48 9.65 1.48 1.48 0.00 0.00 0.37 0.40 0.00 0.00 
4/ 4173 34.0 71.12 34.79 2.21 2.58 0.00 0.00 0.68 0.86 0.00 0.00 
21-23/.4/73 48.8 172.72 49.78 31.15 17.68 6.94 2.51 11.43 6.BO 2.06 1.2B 
25/4173 4.1 26.42 5.33 0.92 0.92 0.00 0.00 0.31 0.31 0.26 0.15 
27/4173 24.6 71.12 31.50 10.54 12.92 3.94 1.38 7.08 5.63 4.03 2.60 
6/5173 16.5 40.64 20.83 6.09 6.64 2.09 1.13 3.78 4.88 2.13 1.39 
24/5173 17.0 60.96 16.51 1.48 6.27 1.16 0.55 1.38 1.B5 0.43 0.45 
31 / 5173 13.5 91.44 17.53 4.41 5.54 1.07 0.92 1.91 2.03 0.84 0.72 
5/ 6/73 19.1 71.12 19.81 5.72 6.64 1.17 1.37 2.46 2.99 1.02 0.62 
8/6173 7.6 30.48 9.91 0.28 0.37 0.00 0.00 0.19 0.15 0.00 0.00 
10/6173 44.2 24.81 30.35 3.80 5.94 11.70 13.29 3.00 2.35 
13/ 6173 22.9 60.96 24.89 9.76 13.72 2.07 1.83 6.42 4.83 1.73 1.77 
21/6/73 6.9 30.48 8.38 2.77 3.69 0.01 0.02 0.62 n.aD 0.01 0.00 
23/ 6/73 39.4 40.64 15.00 16.89 9.76 2.31 1.12 8.01 2.99 1.34 1.33 
25/6/73 5.3 20.32 13.21 0.74 1.11 0,02 0.02 O.lB 0.34 0.00 0.01 
ln173 19.8 20.32 13.21 9.76 16.09 1,41 1.15 5.63 2.44 0.80 0.58 
2n173 25.4 50.80 23.11 13.72 9.76 1.31 0.78 4.57 4.65 0.80 0.62 
517/73 14.5 50.80 12.45 2.21 2.77 0.51 0.17 0.13 O. ffi 0.13 O.OB 
12/7/73 30.5 40.64 28.19 3.97 4.71 0.34 0.33 1.01 1.35 0.13 O. l' 
~- 
Effect of contour length on soi I and water loss under maize-cov.pea rotation 
.-~ 
Rainfall Intensity (mm/hrj 12.5 m 37.5 m 
Date mm Run-aff (mm) Soil loss (tons/haj Run·off (mmj Soil loss (consAla) 
Max. Mean 10.2% 19.2% 10.2% 19.2% 9,3% 13.4% 9.3% 13.4% 
2317173 50.8 111.76 48.26 19.26 28.77 1.50 1.72 11.17 7.74 1.69 1.18 
2717173 11.4 24.38 9.91 0.65 0.65 0.01 0.60 0.19 0.19 0.01 0.00 
3017173 20.8 30.48 13.97 1.29 1.29 0.37 0.03 0.34 0.43 0.00 0.00 
1/8173 9.4 20.32 8.81 00.92 0.74 0.00 0.00 0.25 0.25 0.00 0.00 
5/8173 181.8 50.80 29.71 8.96 9.76 0.24 0.61 4.04 4.31 0.07 0.20 
8/8173 63.0 121.92 69.34 15.30 6.64 1.04 0.59 4.05 6.16 0.42 0.40 
3/9173 26.2 50.80 21.59 3.14 3.14 0.01 0.01 0.98 1.29 0.02 0.14 
10/9173 50.8 91.44 49.53 15.30 8.96 1.71 0.44 2.99 4.84 0.48 0.56 
1219173 37.1 40.64 28.19 13.72 8.96 1.23 0.35 4.57 5.10 0.41 0.48 
23/9173 27.9 121.92 33.02 13.72 5.72 1.19 0.04 4.31 4.05 0.30 0.09 
24/9173 34.3 20.32 5.84 11.34 4.98 0.51 0.06 3.16 3.78 0.14 0.05 
27/9173 66.0 81.28 28.70 6.18 4.89 0.09 0.03 2.61 2.58 2.02 0.02 
29/9173 25.9 60.96 27.4 11.34 4.24 0.33 0.01 3.52 3.25 0.07 0.02 
3/ 10173 11.2 30.48 11.18 1.48 0.55 0.02 0.00 0.37 0.31 0.01 0.01 
13/10173 18.2 71.12 25.35 1.75 1.11 0.01 0.00 0.49 0.62 0.01 0.02 
18/10173 5.3 40.64 6.86 0.37 0.37 0.00 0.00 0.09 0.12 0.00 0.00 
20·21/10173 15.0 40.64 12.95 0.92 0.92 0.01 0.00 0.25 0.31 0.02 0.01 
23/ 10173 37.0 71.12 26.42 3.97 1.57 0.03 0.00 0.68 0.62 0.01 0.00 
25/ 10173 15.4 30.48 14.99 2.21 0.65 0.01 0.00 0.28 0.25 0.00 0.00 
27/ 10173 15.8 91.44 19.81 3.23 0.92 0.02 0.00 0.49 0.31 0.00 0.00 
30/ 10173 29.5 81.28 18.29 5.90 1.48 00.03 0.00 0.92 0.55 0.00 0.00 
APPENDIX lc Runoff and soil loss record for iml~vidual rainstorms during 1974 
Fffec r of mulch r"t~ ( ton / hr) on run·off (mill) 
Date Rain/all Intensity (mml hr) 1% 5% 10% 15% 
mm Max. Mean o 2 4 6 NT o 2 4 6 NT o 2 4 6 NT o 2 4 6 NT 
8-10/ 4/ 74 28.70 40.64 9.12 23.51 0.05 0.20 0.00 0.46 24.83 1.20 0.65 0.65 0.83 20.87 1.38 1.38 0.20 1.20 21.53 1.38 1.48 0.83 1.31\ 
2214174 21.5~ 101.60 25.34 13.27 0.42 0.10 0.00 0.37 15.91 0.65' 0.65 0.37 0.32 10.30 0.92 0.65 0.65 0.65 8.31 O.7A 0.83 0.65 0.74 
2814174 38.61 91.44 43.94 21.&3 0.60 0.92 0.00 0.37 26.81 0.97 0.46 0.37 0.32 16.24 0.55 0.92 0.7B 0.83 20.21 1.06 1.06 0.65 0.23 
3/ 5174 54.61 91.44 52.36 23.75 0.46 0.28 0.00 0.46 37.05 1.55 0.74 0.52 0.88 21.53 2.21 1.43 1.15 1.20 37.38 1.57 1.4B 0.92 1.15 
6 / 5174 13.72 81.28 15.20 7.65 0.09 0.09 0.00 0.14 6.99 0.40 0.14 0.19 0.2B 6.00 0.55 0.32 0.29 0.2B 5.67 0.32 0.37 0.23 0.37 
7 / 5/74 21.34 40.64 12.60 9.64 0.23 0.19 0.00 0.46 19.22 0.65 0.2.3 0.23 0.32 6.33 0.97 0.97 0.37 0.46 6.33 0.37 1.02 0.65 0.37 
31/5174 n.n 40.64 21.96 G.~ 0.09 0.09 0.00 0.19 6.99 0.51 0.19 0.23 0.28 5.01 0.83 0.51 0.46 0.51 1.57 0.51 0.55 0.37 0.46 
4/li/74 10.16 40.64 11.82 2.49 0.05 0.05 0.00 0.09 0.28 0.19 0.09 0.09 0.19 3.69 0.37 0.37 0.23 0.28 2.12 0.28 0.32 0.19 0.28 
~/6(74 13.21 50.80 13.51 5.67 0.19 0.19 0.00 0.28 5.67 0.55 0.28 0.23 0.37 6.00 0.92 0.65 0.55 0.6li 3.69 0.65 0.69 0.37 0.60 
6/6/74 41.91 71.12 25.33 33.41 0.46 0.23 0.00 0.19 32.75 1.11 0.46 0.46 0.60 16.25 1.86 1.06 0.92 1.02 36.72 1.11 1.29 0.65 1.11 
9/ 6174 10.16 30.48 13.46 5.67 0.09 0.09 0.00 0.09 6.94 0.19 0.14 0.14 0.19 3.51 0.37 0.2.8 0.28 0.28 1.38 0.19 0.23 0.19 0.28 
16/li/74 14.48 31).48 5.07 6.33 0.28 0.37 0.00 0.37 10.29 0.92 0.55 0.46 0.55 6.33 1.01 0.83 0.65 0.78 5.67 0.74 0.97 0.55 0.83 
21/6174 22.B6 121.92 2B.71 16.57 0.32 0.14 0.00 0.28 23.18 3.32 0.55 0.19 0.37 9.97 3.60 0.83 0.56 0.69 14.92 1.66 0.55 0.46 0.55 
2916/74 9.S5 2G.32 S.38 \.01 0.00 O.OS 0.00 0.13 0.92 0.37 0.18 0.1S 0.18 0.S3 0.28 0.2S 0.18 0.28 0.28 0.28 0.:)7 0.28 0.37 
317174 64.01 121.92 64.00 45.97 1.29 O.17 0.00 0.92 59.84 16.57 1.48 0.74 1.06 37.71 15.18 3.55 1.89 2.21 59.84 14.00 3.32 1.85 1.85 
6(7174 36.83 71.12 42.16 26.81 0.46 0.28 0.00 0.55 2B.1311.42 1.01 0.37 0.74 22.19 8.84 2.63 1.11 1.48 38.11 7.26 1.85 1.29 1.11 
2117174 52.07 71.12 45.72 30.11 0.65 0.37 0.00 0.88 35.07 19.35 1.75 0.69 0.97 22.19 4.48 3.60 1.48 1.75 25.82 13.60 2.77 1.57 1.66 
Effect of mulch raN It on/ hr ) on run-off (mm) 
Date Rainfall Intensity (mm/ hr) 1% 5% 1096 15% 
mm Max. Mean 0 2 4 6 NT o 2 4 6 NT o 2 4 6 NT o 2 4 G NT 
27/ 7/74 21.08 50.80 10.13 2.77 0.19 0.19 0.00 0.19 6.99 1.25 0.55 0.51 0.46 3.60 1.20 0.78 0.55 0.60 4.73 1.11 0.83 0.46 0.74 
3/9/74 14.80 20.32 5.08 3.69 0.46 0.37 0.00 0.92 5.67 1.52 0.74 0.74 0.83 3.69 1.20 1.20 1.G7 1.75 5.67 1 .66 1 .48 , .06 1 .57 
6/9/74 43.70 50.80 17.02 18.88 0.46 0.46 0.00 0.88 21.38 2.03 1,38 0.60 0.46 26.81 1.29 1.95 1.94 1.52 12.28 1.29 1.94 1.1 a 1.57 
27/9174 11.50 30.48 12.70 5.67 0.28 0.09 0.00 0.37 9.31 0.92 0.56 0.28 0.37 4.35 0,.16 0.74 0.65 0.65 2.17 0.65 0.92 0.37 0.74 
2110174 18.80 50.60 23.88 16.90 0.2A 0.09 0.00 0.18 12.28 1.20 0.116 0.18 0.37 4.35 0.27 0.56 0.46 0.42 2.95 0.42 0.56 0.28 0.-46 
~ 
.I.-.-.'  
Effect 01 mulch raIl! (lon/hr) on run-off (mml ~ 
Dilce Rainfall Intensity (mml hr J 1'1(, 5~ 10% 15% 
mm Malt. Mean 0 2 4 6 NT o 2 4 6 NT o ? 4 6 NT o 2 4 6 NT 
4/1 0174 21.20 40.64 13.46 8.64 0.42 0.1S 0.00 0.37 5.34 3.51 0.66 0.18 0.46 6.00 0.78 0.83 0.69 0.65 7.32 0.92 0.92 0.46 0.69 
7 / 10/ 74 10.20 50.80 11.94 5.01 0.09 0.05 0.00 0.09 5.67 1.06 0.18 0.09 0.24 6.33 0.28 0.28 0.18 0.18 2.12 0.23 0.37 0.18 0.32 
8/10/74 11.20 36.58 13.51 7.65 0.18 0.09 0.00 0.18 8.97 2.26 0.18 0.18 0.28 7.00' 0:27 0.32 0.28 0.18 1.85 0.32 0.37 0.18 0.32 
9-10/10174 61.10 81 .28 43.91 40.41 14.44 0.63 0.00 1.38 37 .37 29.44 7.07 1.01 1.75 14.92 13.60 4.48 1.50 1.75 29.45 21.13 19.54 2.40 1.38 
11 / 10/ 74 5.2 10.16 5.08 1.38 0.09 0.00 0.00 0.14 1.48 0.37 0.14 0.00 0.14 0.92 0.14 0.14 0.09 0.09 0.28 0.23 0.32 0.09 0.09 
I 8·2011017 4 16.2 60.96 12.67 6.27 0.14 0.18 0.00 0.28 7.65 3.14 0.28 0.14 0.28 1.98 0.37 0.37 0.43 0.46 0.46 0.46 0.46 0.37 0.46 
4/11/74 34.S 101.60 42.23 15.00 13.2 0.18 0.00 0.37 21.53 20.14 6.66 0.60 0.74 8.06 9.64 3.00 0.97 1.11 15.58 12.61 3.69 1.29 0.97 
Effe!;t of mulch rHI" llons/ ha) on soil loss (ton/hr) 
Date Rainfall Intensity (111111111,) 1% 5% 1f)!f6 15% 
mm Max. Mean a 2 4 6 NT a 2 4 6 NT o 2 4 6 NT o 2 If 6" NT 
8-10/4/74 2A.70 40.64 9.17 1.23 0.00 0.00 0.00 0.00 2.34 0.06 0.05 O. 00 0.06 5.00 0.02 0.04 0.00 0.00 b.89 0.03 0.00 0.02 0.01 
22/ 4/73 21.59 101.60 25.34 0.74 0,03 0,00 0.00 0.00 3.59 O.O~ 0.03 0.01 0.01 7.00 0.01 0.01 0.00 0.00 0.76 0,01 0.01 0.00 0.00 
28/4174 38.61 91.44 42.22 0.43 0.00 0.25 0.00 0.00 8.68 0.01 0.07 0.00 0.03 11.98 0.03 0.01 0.00 0.00 12.20 0.08 0.01 0.00 0.00 
315/74 54.61 81.28 52.36 0.49 0.00 0.00 0.00 0.00 7.11 0.01 0.00 0.00 0.00 12.41 0.02 0.01 0.00 0.00 15.1 0 0.02 0.01 0.00 0.00 
6 / 5/74 13.72 81.28 15.20 0.26 0.00 0.00 0.00 0.00 2.68 0.01 0.01 0.00 0.00 5.28 0.12 0.00 0,01 0.00 4.56 0.01 0.01 0.00 a.no 
7/5174 21.34 40.64 12.50 0.18 0.01 0.00 0.00 0.00 5.03 0.10 0.05 0.00 0.00 4.58 0.03 0.02 0.00 0.00 0.00 0.01 0.01 0.00 0.00 
3115/74 17.78 81.28 21.96 0.10 0.00 0.00 0.00 0.00 2.58 0.Q1 0.00 0.00 0.00 1.92 om 0 .00 O.UO 0.10 U.44 0.08 0.00 am O.Ge 
4/6/74 10.16 40.64 11.82 0.00 0.00 0.00 0.00 0.00 1.05 0.00 0.00 0.00 0.00 1.21 0.00 0.00 0.00 0.00 0.32 0.00 0.00 0.00 O.CO 
5/ 6174 13.21 40.64 13.51 O.OB 0.00 0.00 0.00 0.00 2.48 0.01 0.00 0.00 000 1.88 0.02 0.00 0.00 0.00 0.~2 0.00 0.00 0.00 O.CG 
6/ 6/74 41.91 71.12 25.33 0.27 om OM OM om 7M OM 0.00 0.00 0.00 5.57 0.02 0.01 0.00 0.00 3.04 0.01 0.00 0.00 0 .0:; 
9/6/74 10.16 25.&0 12.67 0.06 0.00 0.00 0.00 0.00 2.91 0.00 0.00 0.00 0.00 0.91 0.01 0.00 0.00 0.00 0.06 0.00 0.00 0.00 0.00 
16/ 6174 14.48 30.4B 5.07 0.17 0.00 0.00 0.00 0.00 4.85 0.00 0.00 0.00 0.00 4.69 0.00 0.00 0.00 0.00 0.86 0.00 0.00 0.00 0.00 
21 / 6/74 22.R6 132.0B 28.71 0.54 0.00 0.00 0.00 0.00 7.62 0.26 0.12 0.06 0.00 4.87 0.4? 0.04 0.06 0.00 4.14 0.12 0 .11 0.06 O.G~, 
29/ 6174 9.65 15.24 6.76 0.01 0.00 0.00 0.00 0.00 1.62 0 .01 0.01 0.00 0.03 0.02 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 ON) 
317174 64.01 132.0B 43.91 1.41 0.01 0.00 0.00 0.00 19.40 0.83 0.16 0.06 0.49 28.14 0.91 0.1 I 0.Q3 0.02 12.89 0.B4 0.31 0.08 om 
6n174 36.83 60.96 33.78 0.23 0.01 0.00 0.00 0.00 12.24 0.83 0.01 0.00 0.01 12.94 0.81 0 .05 0.00 0.01 5.86 0.63 0.01 0.01 0.00 
2117174 52.07 71.12 43.91· 0.40 0.09 0.00 0.00 0.00 ".29 0.43 0.09 0.00 0.01 6.46 0.&/ 0.10 0.01 0.01 4.19 1.10 0.00 0.00 0.00 
EffF.i,;1 of mul..:;h rote ( t on/hr) on ~o; 1 loas {tons/ ha} 
(.laIR Ra infall Int~nsily {mm/ llr } I I)( 5% 10% 15% 
mm M"x. Mean 0 2 4 6 NT 0 2 4 6 NT 0 2 II 6 NT 0 2 'I 6 N7 
27 17 174 48.80 50.80 10.13 0.02 0.00 0.00 0.00 0.00 3.00 0.26 0.01 0.00 0.02 0.14 0.13 0.01 0.00 0.00 0.46 0.12 0.00 a. 09 a .o ~ 
3: 9/74 14 .80 20.32 3.38 0.08 0.00 0.00 0.00 0.00 1.02 0.01 0.00 0.00 0.00 1.18 0.02 0.04 0.00 0.00 1.59 0.01 0.02 0.01 0.0!· 
8/ 9174 43.70 35.56 16.29 OM om OMO~OM ~~~~~ 2.89 0.08 0.02 0.00 0.00 0.85 0.01 0.01 0.01 D.if 
17 . S/74 11 .50 30.48 8.78 0.09 om O.UO 0.00 0.00 1.23 0.01 0.01 0.00 0.02 0.55 0.00 0.00 0.00 0.00 0.33 0.00 0.01 U.OO 0.0;: 
;! / 10174 18.80 35.56 21.95 0.26 0.00 0.00 0.00 0.00 2.32 0.01 0.13 0.00 0.03 0.85 0.05 0.05 0.06 0 .00 0.60 0.01 0.00 0.00 O.OD 
4/10/74 21.20 46.74 14.19 0.28 0.01 0.00 0.00 0.00 7.54 0.27 0.01 0.00 0.01 1.53 0.01 0.00 0.00 0.00 1.~1 0.01 0.00 0.00 0.00 
7 '!()/74 10.20 50.80 20.27 0.26 0.00 0.00. 0.00 0.00 2.25 0.04 0.02 0.00 0.01 1.29 0.01 0.00 0.00 0.00 1.2fl ().O l 0.00 0.00 O.O '~ 
a "10/74 11.20 36.58 13.5/ 0.15 0.00 0.00 0.00 0.00 2.38 0.06 0.01 0.00 0.01 0.91 0.00 0.00 0.00 0.00 0.52 0.00 0.00 0,00 o.or: 
().I~ 'I 0/7 4 61.10 81.28 43.91 0.60 0.27 om 0.00 0.00 6.03 1.17 0.36 0.01 0.00 5.12 1.35 0.26 0.01 0.01 7.55 7.18 1.64 0.18 0.0: 
l ' / 10/74 5.2 10.16 3.38 0,02 0.00 0.00 0.00 0.00 0.11 0.01 0.00 0.00 0.00 0.29 0.00 0.00 0.00 0.00 0.02 0.03 0.01 0,00 o,()( 
18·2011()/ 74 16.2 60.98 12.67 0.17 0.01 0.00 0.00 U.OO 2.36 0.21 0.01 0.00 0.00 0.06 0.02 0.00 0.00 0.00 0.24 0.1 B 0.01 0.02 O.OC) 
4 / 11/74 34.8 101 .60 4L.23 0.43 0.41 0 .06 0.00 0.00 6.56 1.66 0.41 0.07 0.00 6.65 0.88 0.26 0.02 0.00 9.43 6.32 0 .47 0,09 OJ)() 
Effect of contour length on Soil and water loss under barefallow. 
Rainfall Intensity (mmlhrJ 12.5 m 37.5 m 
Date mm Run-off (mm) Soil loss (tonslhaJ Run-off (mm) Soil loss (tons /ha) 
Max. Mean 10.2% 19.2% 10.2% 19.2% 9.3% 13.4% 9.3% 13.4% 
10/4174 28.70 40.64 9.12 6,46 0,20 0.81 0,01 4,58 2.03 0.16 0.01 
22/4174 21 .6 101.60 25.34 11.34 10.95 1,71 3.11 4.05 4.58 1.81 0.01 
28/4/74 38.6 91.44 42.22 1689 19.27 2.26 2.08 13.83 14.67 4.80 8.35 
3/5/74 54.6 81.28 52.36 25.61 17.69 2.95 2.96 16.74 10.92 4.34 2.76 
6 / 5/74 13.7 81.28 15.20 6.27 6.09 1.74 0.63 5.63 3.78 3.76 2.56 
7/5/74 31.3 40.64 12.50 15.31 7:38 2.61 2.61 10.39 2.46 -~ 
Effect of contour length on soi l and water loss under bilrefallow. ...... 
:t 
Ra in fiJ II Intensity (mm/II,) 12.5 "' 37.5 m 
Date nlm Run-off (mm) Soil loss (tonsl"a) Run-off (mm} Soil loss (tons /ha) 
Max. Mean 70.2% 19.2% 10.2% 19.2% 9.3% 13.4% 9.3% 13.45~ 
10/ 4/74 27.70 40.64 9.12 6.46 0.20 0.81 0.01 4.58 2.03 0.16 0.01 
22 / 4174 21.6 101 .60 25.34 11.34 10.95 1.71 3.11 4.05 4.58 1.81 1.23 
28 / 4/74 38.6 91.44 42.22 16.89 19.27 2.26 2.08 13.83 14.67 4.80 8.35 
3/ 5/74 54.6 81.23 52.36 25.61 17.69 2.95 2.96 16.74 10.92 3.34 2.76 
6/ 5/74 13.7 81.28 15.20 6.27 6.09 1.74 0.63 5.63 3.78 3.76 2.56 
7/ 5/ 74 21 .3 40.64 12.50 15.31 7.38 2.61 2.61 10.39 2.46 5.95 2.67 
31 / 5/74 17.8 81.28 21.96 6.09 6.09 0.53 0.69 2.60 2.40 2.71 0.59 
4/ 6/74 10.2 40.64 11.82 3.41 5.17 0.15 0.39 1.72 2.28 1.31 0.60 
5/ 6/74 13.2 40.64 13.51 6.82 7.20 2.14 1.27 2.46 2.46 3.10 1.42 
6 / 6;74 41.9 71.12 25.33 31.95 40.18 5.59 4.35 22.29 7.75 6.47 2.41 
9/ 6/74 10.2 25.40 12.67 2.77 3.51 0.37 0.41 1.57 1.54 1.98 0.81 
16/ 6/74 14.50 30.48 5.07 12.14 12.93 1.88 1.08 5.24 4.98 2.32 1.99 
21 / 6/74 22.9 132.08 28.71 14.52 14.91 6.80 4.61 14.09 18.32 11.55 5.44 
29/ 6/74 9.7 15.24 6.76 0.92 1.66 0.01 0.02 0.18 0.31 0.00 0.01 
3/7/ 74 64.0 132.08 43.91 52.57 49.00 22.10 3.88 24.93 24.94 24.75 19.96 
fl7/ 74 36.8 60.96 33.78 33.54 20.86 14.30 2.68 24.93 23.61 18.28 9.72 
EHect of contour length on soil and water loss under barefallow. 
Rainfall Intensity (mm/hr) 12.5 m 37.5 tri 
Date mm Run·off (mm) Soil loss (tonsiha) Run-off (mm) Soil foss (cons/haJ 
Max. Mean 10.2% 79.2% 10.2% 19.2% 9.3% 13.4% 9.3% 13.4% 
21/7/74 52.1 72.12 43.91 39.88 27.99 9.86 4.03 15.68 24.93 13.56 5.72 
27/7/74 46.80 50.80 10.13 16.18 9.36 2.42 0.25 4.71 5.37 7.47 2.37 
3/ 9/74 14.~ 20.32 3.38 7.38 11.34 1.81 2.70 3.25 2.73 1.65 2.34 
f' / 9174 43.7 35.56 16.89 40.67 25.61 2.23 1.03 1'.69 6.96 1.50 0,98 
27 / 9/ 74 11.5 30.48 8.78 6:09 6.64 0.40 0.30 1.60 1.48 0.24 0.46 
2/10174 18.8 35.56 21.95 6.18 8.57 1.15 0.55 3.52 2.86 0.63 0.52 
4/ 10/ 74 21.2 46.74 14.19 14.45 12.14 1.70 1.20 3.78 5.37 1.50 1.43 
7/10174 10.2 50.80 20.27 4.06 4.98 0.69 0.54 2.03 3.52 1.17 1.31 
8/ 10/74 11.2 36.58 13.51 4.98 4.24 0.42 0.31 1.t'4 2.00 O.BS 0.84 
9-10/10174 61.1 81.28 43.91 43.05 35.91 10,01 3.95 15.94 23.61 22.73 11.07 
11/10174 5.2 10.16 3.38 2.31 2.03 0,10 0.08 0.22 0.25 0.19 0.14 
18-20/10/74 16.2 20.96 12.67 4.80 5.17 1.0 I 0.61 1.23 1.42 1.28 1.06 
4/11174 . 34.8 101 .60 42.23 28.39 24.03 10,33 2.68 12.38 2.46 8,39 6.67 
......... 
~ 
VI 
147 
APPENDIX 2 Texture of the eroded sediments from 
bare fallow plots for Individual rain storms 
Soil texture of th e sediments eroded from bare fallow p lots ( %) 
Date Slope (%) Gravel Sand Silt Clay 
13/ 6/ 72 1 16.1 21.6 35.1 72.2 
13/ 6/ 72 5 10.0 59.2 12.4 18.4 
13/ 6173 10 11.7 52.0 15.1 21.2 
13/ 6/ 72 15 17.6 58.3 8.9 15.2 
16/ 6/ 72 1 3.1 41.0 21.3 34.6 
16 / 6/ 72 5 8.4 62.1 14.5 15.0 
16/ 6/ 72 10 18.5 22.6 24.3 34.6 
16/6/72 15 9.4 71.4 5.2 14.0 
17/ 6/72 1 18.0 31.5 24.0 26.5 
17/6/72 5 2.6 18.9 46.0 32.5 
17/6/72 10 13.1 31.6 25,0 30.3 
17/6/72 15 12.3 44.5 20.9 22.3 
20 / t' / 72 1 9.9 27.4 32.3 30.4 
20/6 /72 5 9.3 38.5 27.9 24.3 
20/ 6/72 10 9.6 67.2 7.1 16.1 
20 / 6/ 72 15 8.7 53.0 14.6 23.7 
23/ 6172 1 21.9 35.0 12.8 30.3 
23/ 6/72 5 10.2 50.6 21.7 17.5 
23/ 6/72 10 8.3 71.9 6.2 13.6 
23 / 6172 15 13.4 34.6 24.3 27.7 
25/ 6/ 72 7.4 59.6 17.4 15.6 
25 / 6/ 72 5 9.4 76.6 5.7 8.3 
25 / 6/72 10 12.0 63.9 8.9 15.2 
25/ 6/72 15 10.5 65.2 9.3 15.0 
28/ 6/ 72 1 12.1 25.0 28.4 35.5 
28/ 6/72 5 8.8 62.0 11.9 17.3 
28/ 6/ 72 10 7.8 70.8 6.3 15.1 
28 / 6/ 72 15 6.2 74.5 7.7 11.6 
3/7/ 72 1 20.2 39.4 lQ.3 21.1 
317 / 72 5 11.2 t'2.5 13.5 12.8 
3/7 / 72 10 13.3 66.2 8.0 12.5 
3/7 / 72 15 9.7 59.£3 11.7 19.0 
417/ 72 1 18.6 23.1 25.4 32.9 
417/ 72 5 10.4 62.2 12.4 15.0 
4/7/73 10 7.3 67.1 8.5 - 17.1 
148 Soil erosion problems on an alfisol in Wt.'st ern Nigma 
Soil texture of the sediments eroded troln bare fallow plots (%) 
Date Slope (%) Gravel Sand Silt Clay 
4nl 72 15 10.0 70.5 9.7 9.8 
8/ 9172 1 31.0 24.6 17.4 27.0 
8/ 9/ 72 5 7.5 64.4 4.8 23.3 
B/9/ 72 10 11.0 48.0 15.0 26.0 
8/ 9n2 15 11.8 62.4 9.8 15.0 
21 / 9/72 1 13.5 59.4 0.4 26.7 
21 / 9/ 72 5 7.0 48.4 17.5 27.1 
21 / 9/72 10 13.2 48.1 21.2 17.5 
21 / 9/ 72 15 13.3 57.6 13.4 15.7 
25/ 9/ 72 1 27.1 21.6 22. B 28.5 
25/ 9/72 5 6.7 50.4 17.5 25.4 
25/ 9172 10 6.3 54.9 16.1 22.7 
Date Slope % Gravel Sand Silt Cla y 
25/ 9172 15 9.1 52.7 13.5 24.7 
26/ 9172 1 No soil loss 
26 / 9/72 5 7.9 71.5 10.5 10.3 
26 / 9172 10 13.0 37.1 19.3 30.6 
26 / 9172 15 12.0 52.8 11 .3 23.9 
3/ 10 / 72 No so i l loss 
3/1 0172 5 5.3 66. 9 9.7 18.1 
3/ 10/72 10 5.3 71.4 7.8 15.3 
3/ 10172 15 B.6 65.4 11 .2 14.8 
7/10/ 72 1 No so'll loss 
7/ 10112 5 8.8 44.4 20.3 26.5 
7/ 10/ 72 10 15.2 53. 1 12.9 18.8 
7/ 10/ 72 15 11.5 42. 1 21.4 25. 0 
11/10172 1 No soi I loss 
11 / 10/ 72 5 12.3 40.S 27. 3 l S.5 
11/10/ 72 10 8.7 fi3.6 10.2 17.5 
11 / 10172 15 9 .2 66.8 9.3 14.7 
19/ 10172 1 No soi I loss 
18/ 10/72 5 8.6 59.1 14.8 17 .5 
18/ 10/72 10 No dat a 
18/ 10112 15 12.7 60.7 10.7 15.9 
Texture of the eroded sediments 149 
Soil texture of the sediments eroded from bare fallow plots (%) 
Date Slope % Gravel Sand Silt Clay 
4/4173 1 36.0 55.6 4.2 4.2 
4/4173 5 33.6 45.2 10.1 11.1 
4/4/73 10 22.2 56.0 8.6 13.2 
4/ 4173 15 20.4 41.4 17.5 20.7 
23/4173 17.9 23.0 24.6 34.5 
23/4173 5 16.0 31.9 26.9 25.2 
23/ 4173 10 16.0 60.5 9.2 14.3 
23/4173 15 20.4 41.4 17.5 20.7 
25/4173 No soil loss 
25/4173 5 8.7 58.4 14.6 18.3 
25/4173 10 9.7 34.7 6.5 9.1 
25/4173 15 7.6 62.6 10.7 19.1 
27/4173 15.0 24.7 3.8 29.6 
27/4173 5 14.0 50.8 17.4 17.8 
27/4173 10 38.8 43.3 4.7 13.2 
27/4173 15 17.2 58.8 11.4 12.2 
6/5173 1 23.0 30.8 20.2 26.0 
6/5173 5 12.3 62.3 11.4 14.0 
6/5173 10 12.3 64.9 9.8 13.0 
6/5173 '5 9.1 70.9 7.3 12.7 
24/5173 1 30.6 41.4 13.6 24.4 
24/5173 5 12.3 57.7 12.8 17.2 
24/5/73 10 19.0 56.1 11.0 13.9 
24/ 5/ 73 15 15.4 66.6 7.3 10.7 
31 / 5173 1 27.1 18.4 25.9 28.6 
31 / 5173 5 21.0 44.4 17.9 16.7 
31 / 5173 10 31 .3 44.8 10.0 13.9 
31 / 5173 15 28.5 51.0 11.2 23.8 
5/ 6/73 1 24.7 29.2 22.3 23.28 
5/6/73 5 18.4 59.0 8.6 14.0 
5/6/73 10 14.2 62.8 10.0 13.0 
5/6173 15 10.2 70.8 8.6 10.4 
8/6/73 1 No soi I loss 
8/ 6173 5 14.2 68.0 7.4 10.4 
8/ 6173 10 11.9 68.9 7.6 11.6 
150 Soi I erosion prohl ems on an aUi sol in Western Nigeri a 
Soi. texture of the sediments eroded from bare fallow plots (%) 
Date Slope % Gravel Sand Silt ClaV 
8/6n3 15 7.5 77.0 5.2 10.3 
10 / 6173 1 30.9 24.0 23.2 21.9 
10/ 6/ 73 5 21.7 57.0 9.9 11.4 
10/ 6173 10 25.0 63.3 6.5 5.2 
10/ 6173 15 14.B 63.0 9.9 12.5 
13 / 6 / 7 3 1 22.3 27.3 26.1 24.3 
13 / 6173 5 16.1 65.2 8~9 9.7 
13 / 6173 10 14.6 65.9 6.5 13.0 
13 / 6173 15 19.3 59.1 11.0 10.6 
21 / 6/73 No soil loss 
21/6173 5 6.6 80.1 7.1 6.2 
21 / 6/73 10 10.4 71.8 7.7 10.1 
21/6173 15 11.5 71.0 8.5 9.0 
23/ 6173 31.1 40.8 14.9 13.2 
23/'6173 5 9,5 71.3 8.7 10.5 
23/ 6173 10 9.1 61.1 14.2 15.6 
23/6173 15 11.7 67.8 8.5 12~0 
25 / 6173 1 No soi l loss 
25/ 6173 5 9.9 70.4 9.5 10.2 
25/6173 10 4.3 78.5 8.2 14.9 
25/ 6173 15 8.6 77.0 F.O 8.4 
117173 1 22.B 27.8 25.9 23.5 
117173 5 10.7 70.8 8.8 9.7 
117173 10 8.2 58.9 9.5 13.4 
1/ 7173 15 24.4 59.1 7.0 8.9 
2/ 7173 31.2 36.6 17.6 14.6 
2/ 7173 5 6.9 78.2 5.6 9.3 
217173 10 8.2 73.5 7.0 11.3 
217173 15 13.0 71.4 9.6 9.0 
517173 1 25.0 28.5 22.2 24.3 
517173 5 10.0 75.8 B.8 5.4 
517173 10 1 B.6 62.8 7.3 11.3 
5/7173 15 11.5 69.1 9.0 10.4 
1217173 20.9 45.3 18.2 15.6 
1217173 5 9.5 66.1 12.3 12.1 
1217173 10 8.9 72.0 7.5 11.6 
1217173 15 6.9 73.5 11.2 8.4 
Texture of the eroded sediments lSi 
Soil texture of the sediments eroded from bare fallow profs (%) 
Date Slope % Gravel Sand Silt Clay 
2317173 1 33.1 32.9 20.1 13.9 
2317173 5 12.6 66.5 10.1 10.8 
2317n3 10 17.0 59.1 9.6 14.3 
2317173 15 14.3 59.3 13.4 13.0 
Zl/7173 1 No soil loss 
Zl17173 5 13.9 65.4 9.6 11.1 
27/7173 10 12.0 73.7 9.4 14.9 
2717n3 15 18.9 59.2 10.6 10.3 
3(}/7n3 1 No soi I loss 
30n173 5 8.3 71.7 9.7 10.3 
30/7173 10 13.8 68.1 7.4 10.7 
3017/73 15 10.2 74.7 5.9 9.2 
118/73 25.5 45.6 13.4 15.5 
1/8173 5 5.9 76.4 8.1 9.6 
l/a173 10 20.6 66.7 4.1 8.6 
118173 15 8.8 75.7 6.4 9.1 
5/8/73 1 8.2 31.4 31.0 29.4 
5/8173 5 13.6 46.6 22.5 17.3 
518/73 10 11.6 43.5 23.7 21.2 
5/Sn3 15 18.0 63.3 8.9 9.8 
8/8/73 1 27.0 30.7 25.5 16.8 
8/S173 5 9.0 42.0 31.7 17.3 
8/8/73 10 19.2 64.0 7.1 9.7 
8/8n3 15 17.2 67.6 6.6 8.6 
3/9173 1 No soil loss 
3/9173 5 16.7 43.3 16.7 23.3 
3/9/73 10 8.8 40.1 26.4 24.7 
3/9173 15 8.2 72.9 8.4 10.5 
10/9173 1 7.9 33.3 33.0 25.8 
10/9173 5 25.2 59.5 6.0 9.3 
10/9173 10 2.0 29.4 33.3 35.3 
10/ 9173 15 6.3 40.5 27.9 25.3 
12/9n3 1 24.2 49.7 11.6 14.5 
12/9173 5 6.6 24.7 38.5 30.2 
1219173 10 6.8 35.0 98.0 30.2 
12/ 9173 15 15.2 58.0 13.7 13.1 
17/9173 1 No soil loss 
152 Soil erosion problems on an alfisol in Western Nigeria 
Soil texture of the sediments eroded from bare fallow plots (%) 
Dete Slope % Graver Sand Silt Clay 
17/9;73 5 15.7 62.4 11.8 10.1 
17/9173 10 8.3 77.5 5.6 9.6 
17/9173 15 12.9 67.3 8.5 11.3 
23/9;73 1 27.5 17.7 24.8 30.0 
23/9173 5 12.8 42.2 24.6 20.4 
23/9173 10 26.9 56.7 6.6 9.8 
23/ 9175 15 No soU loss 
24/9173 1 23.5 41.3 19.1 16.1 
24/9173 5 22.8 60.5 7.1 9.6 
24/9173 10 19.1 67.8 4.4 8.7 
24/9/73 15 24.8 59.4 6.8 9.0 
27/9173 25.2 36.1 20.0 18.7 
27/9173 5 13.1 68.9 9.4 8.7 
27/9/73 10 12.1 73.6 3.9 10.4 
27/9/73 15 12.6 68.2 7.0 12.2 
29/9/73 1 26.7 56.3 9.1 7.9 
29/9/73 5 No soil loss 
29/9/73 10 24.8 61.4 6 .0 7.8 
29/9/73 15 23.2 63.1 6.0 7.7 
3/10/73 1 22.2 38.7 19.8 19.3 
3/10173 5 5.4 7.9 4.9 9.8 
3/10/73 10 18.6 69.0 3.6 8.8 
3/10/73 15 12.3 77.1 3.5 7.1 
13/10173 1 No so i l loss 
13/10173 5 7.1 69.8 11.9 11.2 
13/10173 10 19.3 62.0 7.6 11.1 
13/10173 15 19.1 68.1 4.7 8.1 
18/ 10/73 No soil loss 
18/10/73 5 7.7 77.7 4.4 10.2 
18/10/ 73 10 18.6 64.3 5.7 11.4 
18/10/73 15 14.3 69.4 7.7 8.6 
20/10/73 1 23.2 61.1 8.0 7.7 
20/10;73 5 9.4 67.2 12.5 10.9 
20/ 10/73 10 8.3 70.6 8.3 12.8 
20/ 10173 15 11.0 73.3 9.4 9.3 
23/ 10173 1 22.8 37.5 18.1 16.6 
23/10173 5 17.6 63.3 8.6 10.5 
23/10173 10 11.5 67.3 7.1 14.1 
Texture of the eroded sediments 153 
Soil texture of the sediments eroded from Dare fallow plots {%) 
Date Slope % Gravel Sand Silt Clay 
23/10n3 15 14.8 69.5 6 .0 9.7 
25/10173 1 11.1 12.4 39.1 37.4 
25/10173 5 50.0 34.4 7.2 8.4 
25/10173 10 16.6 73.8 2,6 7.0 
25/10173 15 11.3 75.2 3,9 9,6 
27/10173 8.8 75.7 7.3 8.2 
27/10/73 5 14.8 59,6 14.5 11.1 
27/10/73 10 17.2 63.9 7.3 11.6 
27/10173 15 27.1 23,1 24,8 25.0 
30/10173 27.3 30.0 23.1 19.6 
30/10173 5 13.0 67.3 8.9 10.8 
30/10173 10 19.5 67.3 4.8 8.4 
30/ 10173 15 15.7 68.3 7.6 8.4 
APPENDIX 3 Unit 1 
Appendix erosivity indices 
Total E EI30 KE 71 
Date foot-ton 130 foot-ton foot-ton R 
per acre in/hr per acre inch per acre 
19/5/72 464,1 0.85 394.5 464.1 3.95 
4/5/72 673.9 1.20 808.7 2000.0 8.09 
e/5/72 199.1 0.43 86.0 168.7 0.86 
9/ 5 / 72 292.9 0.65 190.4 141.3 1.90 
11 517 2 400.2 0.85 320.2 282.6 3.20 
14/5/72 526.4 1.10 645.0 508.0 6.45 
27/ 5/ 72 176 .8 0.40 70.7 0.0 0.71 
28/ 5172 1614.2 1.50 2421.3 801.3 24.21 
29/ 5/ 72 236.0 0.50 118.0 196.8 1.18 
31 / 5/ 72 381.6 0.80 305.3 254.0 3.05 
1/6172 1778,2 2.40 4267,7 1611,4 42.68 
2/6172 127.6 0.30 38.3 0,0 0.38 
4/6/72 327.4 0.70 229.2 254.0 2.29 
7 / 6172 308.4 0.70 215.9 114.5 2.16 
9/6/72 358.1 0.70 250,7 358.1 2,51 
11/6/72 165.6 0,40 66.4 0.0 0.66 
13/6172 1633.8 1.10 1797.2 1163.0 17.97 
16/6/ 72 415.9 0.90 374.3 254.0 3.74 
17/ 6172 4563.2 4.80 21903.2 4523,8 219,03 
18/6/72 249.4 0.30 74.8 OJ) 0.75 
20/6 /72 301 .1 0.30 90.3 254.0 0.90 
22/ 6/72 126.6 0.20 25.3 0.0 0,25 
23/ 6 / 72 236.0 0,50 118.0 196.8 1.18 
24/6172 192.9 0,45 86.8 114.5 0.B7 
25/6/ 72 966.0 1,10 1062.6 569.2 10.62 
28/6/72 254.0 0.50 127,0 254.0 1.27 
1/7/72 88.4 0.20 17.2 0.0 0.17 
2/7/72 102.4 0.15 15.4 0.0 0.15 
317172 613.8 1.15 705.9 557.5 7.06 
4/7172 332.4 0.70 232.7 254.0 2.33 
517172 166.8 0.20 33.4 0.0 0.33 
1217172 1031.2 1.70 1753.0 766.0 17.53 
1717172 256.1 0.60 153.7 114.5 1.54 
156 Soil erosion problems on an allisal in Western Nigeria 
APPENDIX EROSIVITY INDICES 
Total E EI 30 KE 71 
Date foot·ton 13() foot-ton foot·ton R 
per acre inlhr per acre inch per acre 
25/8/72 663.6 1.10 730.0 433.2 7,30 
5/9172 191.0 0.30 57.3 0.0 0.57 
6/9/72 441.2 0.60 264.7 196.8 2.65 
7/ 9/72 429.7 1.00 429.7 430.0 4.3D 
8/9/ 72 390.8 0.50 195.4 254.0 1.95 
11/9/72 201.0 0.30 60.3 0.0 0.60 
16/9/72 473.7 1.0 473.7 395.3 4.74 
21/9/72 1136.3 1.25 1420.4 754,3 14.20 
24/9/72 230.2 0,35 80.6 0.0 0.81 
25/9/ 72 474,4 1.00 474.4 312.6 4.74 
26/9/72 309.4 0,60 185,6 196.8 1.86 
27/9 / 72 127.6 0,30 38,3 0,0 0.38 
3/ 10/72 278,1 0,45 125,1 141,3 1,25 
7/10172 170 ,8 0,40 68.3 114,5 0,68 
9/10/72 575.5 1.20 690,4 495.0 6.90 
10/10/ 72 196,8 0.40 78.7 197,0 0,79 
12110172 175.5 0,50 87,8 141,3 0,88 
18/10172 293,2 0,68 199,4 254,0 2,00 
19/ 10 / 72 156,8 0,30 47,0 0,0 0,47 
Appendix erosivity indi ces 157 
UNIT I) 
APPENDIX EROSIVITY INDI CES 
(b) 1973 
Total E I 30 EJ30 KE 71 
Date foot-ton foot-ton foot-ton R 
per acre in/hr per acre inch par acre 
2/1173 532,0 1.00 532.0 338.1 5.32 
212113 156.8 0.40 62.7 0.0 0.63 
1712173 342,4 0.70 239.7 254.0 2.40 
4/3173 105.5 D.25 26,4 0.0 0.26 
16/ 3/ 73 689.3 0. 70 482.5 141.3 4.83 
2213/73 235.2 0.20 47.0 0.0 0.47 
25 / 3/73 332.4 0.70 232.7 254.0 2.33 
29/ 3/ 73 400.7 0.40 lEO .3 141.3 1.60 
30/ 3/73 268.9 0.50 134.5 141.3 1.35 
4/4173 1253.5 1.90 2381.6 967.6 23.82 
6/4173 166.8 0.50 83,4 0.0 0,83 
9/4173 126.4 0.30 37.9 0.0 0.38 
14/4/73 173.9 0,25 43,5 0.0 0,44 
15/4173 43.8 0.10 4.38 0.0 0.04 
20/4173 1618.2 3.00 4854.6 1441.4 48.55 
23/4/73 343.6 0,80 274.9 0.0 2,75 
25/4/73 152.6 0.32 48,8 0.0 0.49 
27/4/73 945.8 1.80 1702.4 8b7.4 17.02 
4/5173 196.8 0.40 78.7 196.8 0.79 
6/5/73 557.8 1,30 623.2 479.4 6.23 
9/ 5/73 201.0 0.52 104.5 0.0 , .05 
22/5/73 381,0 0.70 266.7 312.6 2.67 
24/5/73 634.4 1.30 824.7 595.2 8,25 
23/5173 133.4 0.36 48.0 94.2 0,48 
31/5173 555.5 1 06 588.8 495,0 5.89 
5/6/73 704.7 1.20 845.6 513.7 8.46 
8/6/73 270.2 0.60 162.1 197.0 1.62 
13/ 6173 861.0 1.40 1205.4 685.0 12.05 
21 / 6173 268.9 0.60 161.3 141.3 1.61 
23/ 6173 1402.6 1.0 1402,6 873.0 14.03 
25/6173 187.1 0,42 78.6 0.0 0.79 
30/6/73 718.6 0.90 646.7 513.7 6.47 
1/7173 627.2 0,80 501,8 0.0 5,02 
217173 963.1 1.50 1444.7 707.9 14,45 
5/7173 489.0 0,90 440.1 254,0 4,40 
1217173 1063.8 1.30 1382.9 450.8 13,83 
158 Soil erosion problems on analfisol in Westem Nigeria 
APPENDIX EROSIVrTY INDICES 
(b) 1973 
Total E r 30 EI30 KE 71 
Date foot-toil inlhr foot·ton foot-ton R 
per acre per acre inch per acre 
23/7/73 2199.2 3.50 7697,2 1934.0 76.97 
27/7/73 366.5 0.60 220.0 141.3 2,20 
30/7173 513.9 0.90 462.5 141.3 4.63 
1/8173 299.4 0.50 150.0 0.0 1.50 
2/8/73 111.4 0.30 33.4 0.0 0.33 
4/8173 2774.8 2.00 5549.6 2323.6 55.50 
5/8/73 3083;3 1.80 5549.9 1382.4 55.50 
8/8/73 2578.2 3.70 9539.3 2298.8 95.39 
16/8173 276.8 0.40 110.7 208.4 1.11 
23/8173 265.2 0.60 159.1 0.0 1.59 
24/8173 372.8 0.70 261.0 0.0 2.61 
1/9/73 366.5 0.90 329.9 141.3 3.30 
3/9173 842.B 1.20 1011.4 450.8 10.11 
8/9/73 489.& 0.40 195.8 0.0 1.96 
10/9173 2017.8 2.90 5851.6 1552.4 58.52 
12/9173 1447.3 1.1 0 1592.0 928.5 15.92 
14/9173 167.6 0.40 67,0 0.0 0.67 
17/9173 254.0 0.50 lZ7.0 0,0 1.27 
23/9173 1203,0 2.10 2526,3 1134.5 25.26 
24/9173 1281.1 1.65 2113.8 771.3 21.13 
27/9/73 773.8 1,30 1005,9 509.4 10.06 
28/9173 269,0 0.50 134,0 234,8 1.34 
29/9173 1038.7 1.90 1973.5 881.8 19,74 
1/10173 363.6 0.80 290.9 198.7 2.91 
3/10/73 386.6 0.70 270.6 141.3 2.71 
6/10173 201.0 0.50 105.0 0,0 1,05 
13/10173 666.2 1,10 732.8 509.4 7.33 
18/10173 244,7 0.46 112.6 245.0 1.13 
20/10173 363.6 0,80 290.9 197.9 2.9J 
21/10173 128.4 0.30 38.5 94,2 0,39 
23/10173 797.5 1,30 1036.8 453.9 10.37 
25/10/73 440.8 0,90 396,7 141,3 3.97 
27/10173 690.0 1,20 756.0 630.0 7.56 
30/10173 1064.1 1.1 1170.5 907.3 11,71 
31/10/73 78,4 0.20 15.7 0.0 0.16 
14/12/73 265.2 0.50 132.6 0,0 1.33 
Appendix e rosiv ity indices 159 
APPENDIX EROSIVITY INDICES 
(e) 1974 
Total E 130 EI30 KE 71 
Date foot-ton in/hr foot-ton foot-ton R 
per acre per acre inch rer acre 
7 /3/74 371.6 0.88 327.0 254.0 3.27 
11 / 3174 358.0 0.50 179.0 0.0 1.79 
24 / 3174 1472,0 1.80 2649,6 1226,7 26.50 
25/ 3174 652,9 1,30 848,8 574,5 8.49 
1/ 4174 1621,0 2.70 4376,7 2120,2 43.78 
3/4174 180.5 0.40 72,2 141.3 0.72 
10/ 4/74 300.3 0,50 150,0 197,0 1,50 
14/4174 777.2 1,40 1088.1 699,0 10.88 
15/4174 214.9 0.50 107.5 141.3 1.08 
16/4/74 391,5 0.70 274,0 141,3 2,74 
21 / 4174 208,4 0.20 41.7 0,0 0.42 
22/4174 808.6 1,50 1212,9 1265.4 12.13 
3/5/74 2040.1 2.50 5100.2 1520.8 51.00 
6/ 5174 467.4 1,00 467.4 433,2 4.67 
7/5174 720.2 0,50 360.1 338,1 3.60 
13/5174 150.0 0.30 45.0 0.0 0.45 
31 / 5174 662.5 1.20 795,0 534,9 7,95 
4/6174 285.2 0.80 228,1 196.8 2.28 
5/ fi174 463.8 0,80 371,0 395.3 3,71 
6/ 6174 1486.9 1,40 2081,7 655.0 20.82 
9/6/74 357,3 0.80 285,8 141.3 2.86 
11 / 6/74 175,5 0,40 70.2 141,3 0.70 
15/ 6174 568.5 1.0 568.5 372.4 5,69 
1E16/74 483,0 0,3 144.9 170.0 1,45 
21 / 6/74 977,8 1,8 1760,0 938,6 17,60 
29/ 6/74 269,4 0.4 107.8 0.0 1.08 
30/ 6174 78.4 0,20 15.7 0.0 0,16 
3/7/74 4003.8 2,10 8408.0 1536,8 84.08 
6/7/74 1265. 7 1,90 2404.8 102(l,5 24.05 
10/7/74 150,0 0.30 45.0 0,0 0,45 
17/7/74 214.7 0.50 107.3 141,3 1,07 
21/7/ 74 1690.5 2.10 3550,1 1331,1 35,50 
2717/74 651.2 0,60 390,7 254.0 3.91 
160 Soil erosion problems on an allisol in Wes tern Nigeria 
APPENDIX EROSIVITY INDICES 
(c) 1974 
Total E 130 EI30 KE 71 
Date foo1:-ton inlhr foot-tt'n foot-1on R 
per acre per acre inch per acre 
3017174 270.2 0.40 108.1 196.8 1,08 
15/ 8174 141.3 0.30 42.4 141.3 0,42 
28/ 8174 327.4 0.74 242.3 254.0 2.42 
30/ 8/74 505,1 0.90 454.4 348.2 4.54 
1/ 9/ 74 923.1 1.20 1107.7 521.1 11 .08 
4/ 9/ 74 362,4 0,30 108,7 0.0 1.09 
519174 254,4 0,40 127,2 0,0 1.27 
6/ 9/74 1312,4 0,9 1181,2 196,8 11.81 
17/ 9/74 231.1 0,50 115,5 196,8 1.16 
23/ 9/ 74 305.3 0.60 183,2 168.7 1.83 
27/9/ 74 316.8 0.70 221,8 282,6 2.22 
2/ 10174 693,5 1,20 832,2 536.6 8.32 
4/ 10174 ~ 798,0 0.80 638,4 558,2 6,38 
5/ 10/ 74 376.5 0,40 150.6 141,3 1,51 
7/ 10174 381.4 0,70 267,0 268.5 2,67 
8/ 10174 358.6 0,70 251,0 196.8 2.51 
9/ 10174 1487,2 1,50 2230,8 1379.5 22.31 
10/ 10174 543,5 0.90 489,1 141.3 4.89 
11 / 10/74 137,0 0,20 27,4 0.0 0.27 
20 / 10174 432,8 0.70 303,0 330.0 3,03 
30/10174 166,8 0,40 66 ,7 0,0 0.67 
3/ 11/74 1330,1 1,40 1862,1 1207.5 18.62 
APPENDIX 4a Soil moisture records for 1972 
NEUTRON PROBE EVALUA nON 
Plot No. Depth in Mol sture Content (g l g) 
em 10/ 12111 17112171 23112171 31 / 12171 611172 1311172 29 / 1172 10/ 2/ 72 24 / 2172 2/3/ 72 17/ 3/72 
30 .986 .151 .130 .124 .126 .104 .123 .125 .071 .148 .100 
1 60 .196 .220 .207 .211 .221 .223 .201 .205 .151 .214 .207 
ro .271 .274 .265 .282 .284 .2B6 .283 .280 .251 .215 .259 
120 .298 .288 .288 .295 .292 ..297 .295 .2C35 .294 .305 .285 
30 .033 .070 .066 .058 .064 .054 .050 .054 .005 .054 .131 
2 60 .130 .232 .229 .226 .229 .218 .227 .233 .120 .193 .225 
ru .282 .211 .265 .210 .268 .263 .269 .266 .263 .283 .260 
120 .218 .273 .210 .277 .274 .273 .216 .277 .210 .280 .217 
30 .032 .076 .078 .073 .067 .063 .059 .054 .016 .088 .118 
3 60 .105 .176 .185 .175 .172 .172 .167 .166 .085 .142 .196 
ro .253 .259 .260 .262 .254 .253 .256 .251 .236 .266 .22~ 
'20 .216 .268 .275 .290 .268 .267 .267 .268 .271 .299 .256 
30 .028 .096 .084 .085 .075 .015 .012 .061 .016 .012 .098 
4 60 .036 .179 .182 .179 .175 .174 .172 .168 .124 .174 .177 
ro .235 .289 .251 .252 .251 .248 .246 .240 .218 .247 .231 
-TaJ_ ._- .305 .305 .298 .304 .302 .295 .293 .289 .211 .291 .256 
30 .051 .075 .082 .082 .075 .010 .067 .080 .021 .103 .109 
60 .134 .188 .200 .200 .190 .192 .190 .198 .100 .163 .114 
5 
00 .251 .265 .272 .271 .264 .265 .266 .273 .228 .252 .198 
120 .284 .282 .288 .286 .280 .284 .281 .287 .269 .282 .205 
6\ 
1-00 
.~.....  
Plot No. Depth in Moisture Content f91 g) 
em 10/12/71 17/12171 23/12/71 31/12/71 611/72 1311/72 29/1/72 10/2/72 24/2/72 213172 1713/72 
30 .116 .101 .075 .081 .085 .075 .076 .074 .024 .128 .119 
6 60 .204 .204 .187 .193 .192 .187 .187 .190 .131 .203 .225 
g) .253 .252 .254 .254 .263 .249 .248 .251 .231 .251 .289 
720 .286 .282 .281 .265 .281 .277 .278 .276 .264 .279 .300 
30 .143 .114 .103 .103 .102 .086 .100 .104 .003 .104 .123 
7 60 .216 .207 .209 .205 .205 .206 .203 .206 .192 .259 .271 
90 .250 .243 .248 .242 .242 .335 .241 .143 .219 .250 .277 
120 .279 .266 .267 .266 .265 .263 .269 .263 .252 .270 .290 
30 .102 .089 .084 .076 .079 .071 .063 .065 .010 .075 .075 
8 60 .193 .183 .178 .176 .179 .176 .175 .177 .109 .132 .174 
g) .248 .236 .236 .239 .23Q .232 .232 .229 .221 .251 .256 
120 .269 .258 .257 .260 .259 .254 .252 .255 .251 .249 .300 
30 .153 .136 .110 .119 .114 .095 .094 .092 .032 .049 
9 60 .190 .180 .169 .175 .177 .169 .170 .170 .132 .135 .141 
g) .243 .227 .223 .229 .230 .223 .226 .225 .198 .193 .260 
120 .271 .261 .257 .264 .259 .257 .260 .255 .234 .254 .275 
-------- --------
30 .113 .090 .079 .070 .079 .073 .073 .069 .027 .094 .102 
10 60 .171 .159 .154 .154 .152 .146 .143 .143 .105 .166 .209 
g) .207 .195 .192 .188 .194 .186 .1 fl9 .lR9 .171 .196 .263 
720 .227 .218 .211 .208 .215 .204 .206 .206 .1 90 .206 .282 
, - .-------~~-.----
Plot No. Depth in Moisture font~~.~Jg/gL 
em 10/12/71 17/12171 23/12/71 31112171 6/1172 1311172 29/1/72 10(2.(72 2412172 213172 17/3/72 
30 .019 .030 .026 .037 .035 .014 .074 .066 
11 60 .098 .118 .119 .137 .140 .062 .123 .132 
[lJ .197 .201 .194 .200 .198 .190 .202 .206 
120 .186 .193 .185 .196 .191 .196 .207 .194 
30 .046 .049 .047 .043 .037 .054 .059 .056 .084 
12 60 .146 .156 .153 .150 .147 .162 .160 .123 .179 
[lJ .205 .203 .206 .198 .198 .211 .204 .190 203 .214 
120 .216 .213 .211 .206 .207 .214 .212 .211 .229 .223 
30 .033 .032 .037 .025 .024 .028 .083 .068 .068 
13 60 .170 .147 .149 .148 .138 .143 .145 .154 .091 .148 .170 
90 .189 .187 .186 .183 .185 .lS0 .192 .181 .192 .203 
120 .202 .200 .198 .194 .200 .206 .207 .205 .214 .218 
30 .041 .061 .059 .054 .051 .051 .058 .091 .086 
14 60 .156 .154 .147 .144 .144 .143 .162 .077 .128 .169 
ro .197 .197 .195 .188 .188 .197 .197 .184 .199 .198 
120 .205 .208 .206 .197 .200 .208 .212 .208 .212 .211 
30 .037 .010 .018 .017 .048 .005 .018 .009 .047 068 
15 60 .127 .109 .117 .109 .094 .097 .103 .050 .105 .121 
ro .179 .171 .171 .166 .159 .166 .165 .145 .154 .165 
120 .244 .237 .235 .228 .223 .226 .227 .195 .199 .228 
8-l 
f 
Plot No. Depth in Moi sture Content (g/ g) 
em 10/12n1 17/12111 23/12111 31/12171 6/1n2 13/1172 29/1/72 10.'2172 24/2112 2/3/72 17/3/72 
30 .043 .026 .028 .015 .014 .003 .021 .039 .053 
16 60 .181 .165 .167 .158 .158 .139 .160 .061 .147 .166 
EJJ .206 .202 .197 .197 .196 .202 .203 .194 .213 .211 
120 .216 .212 .209 .207 .205 .211 .213 .203 .214 .218 
30 .028 .012 .021 .010 .012 .012 .011 .003 .048 
17 60 .125 .119 .127 .114 .113 .121 .127 .056 ,098 .164 
ro .175 .173 .174 .167 .170 .176 .175 .171 .172 .172 
120 .175 .194 .194 .191 .193 .199 .201 .187 .189 .209 
30 .009 .011 .OOB .014 .018 .011 .036 .041 
18 60 .029 .028 .027 .035 .035 .027 .058 .045 
90 ,061 .062 .060 .068 .066 .050 .065 .066 
120 .074 .073 .075 .081 .078 .069 .078 .087 
30 .005 .007 .008 .002 .004 .005 .007 .032 .038 
19 60 .020 .018 .018 .018 .026 .027 .019 .063 .057 
9D .024 .024 .025 .026 .034 .036 .032 .065 .058 
120 .043 .043 .044 .045 .053 .053 .045 .067 .064 
30 .007 .004 .002 .003 .005 .003 .021 .025 .037 
20 60 .019 .018 .017 .018 .025 .023 .021 .046 .037 
00 .027 .025 .025 .025 .034 .032 .028 .043 .045 
120 .032 .032 .032 .033 .042 .042 .037 .044' .062 
Plot No. Depth in Moisture Content (~/ g) 
em 10/12nl 17112nl 23/12171 31112171 6/1172 13/1/12 29/1112 10/2172 2412.172 2/3172 17/3112 
30 .002 .003 .009 .004 .008 .011 .007 .024 0 
21 60 .016 .016 .016 .016 .024 .024 .028 .067 .058 
9J .023 .024 .025 .028 .034 .033 .030 .069 .060 
120 .027 .031 .032 .033 .041 .040 .038 .065 .053 
30 .008 .005 .005 .003 .008 .007 .007 .009 .050 
22 60 .012 .012 .013 .013 .021 .020 .021 .069 .047 
ro .014 .015 .017 .016 .027 ~O27 .021 .048 .049 
120 .034 .041 .042 .044 .053 .056 .038 .053 .070 
30 .015 .019 .011 .008 .009 .015 .008 .015 .010 .038 
23 6D .021 .025 .022 .021 .022 .030 .028 .026 .058 .043 
ro .044 .050 .045 .044 .044 .052 .050 .035 .049 .071 
720 .138 .081 .078 .076 .079 .087 .083 .074 .083 .089 
30 .016 .016 .013 .011 .008 .013 .013 .006 .016 .034 
24 ro .011 .011 .012 .011 .012 .018 .018 .022 .049 .036 
fJJ .013 .016 .017 .017 .017 .026 .028 .018 .038 .049 
120 .047 .051 .052 .051 .051 .057 .058 .1)48 .071 .071 
~ 
Vl 
~ 
Plot No, Depth in Moisture Content (g/g) • 
an 6/4/72 20/4/72 2714172 415172 ,1'15/72 18/5112 2(;/5112 1/6/72 8/6172 15/6172 26/6/72 
30 .115 .116 .175 .175 .142 .102 .194 .191 .208 .210 
1 60 .177 .197 .207 .206 .208 .201 .250 .213 .231 .251 
ro .283 .267 .266 .257 .267 .261 .287 .278 .293 .281 
120 .300 .296 .294 .286 .297 .287 .304 .300 .312 .305 
30 .85 .149 .136 .132 .125 .096 .076 .131 .121 .128 .140 
2 60 .241 .268 .267 .261 .253 .237 .219 .242 .228 .241 .245 
90 .295 .276 .279 .285 .298 .281 .256 .260 .274 .280 .278 
120 .283 .279 .279 .283 .296 .285 .269 .271 .275 .278 .283 
:JJ .149 .171 .162 .153 .138 .160 .154 .157 .175 
3 60 .211 .216 .228 .223 .213 .215 .209 .206 .235 
ro .285 .290 .302 .3(5 .297 .293 .291 .286 .309 
120 .305 .292 .318 .329 .317 .319 .324 .321 .335 
30 .067 .160 .181 .145 .108 .085 .143 .162 .164 .129 
4 60 .146 .206 .208 .200 .206 .161 .167 .179 .185 .175 
ro .250 .283 .289 .281 .296 .264 .266 .272 .278 .274 
120 .274 .284 .290 .283 .288 .282 .282 .282 .284 .281 
30 .083 .144 .123 .138 .129 .102 .076 .142 .149 .151 .165 
5 60 .188 .225 .222 .198 .210 .198 .177 .229 .230 .233 .234 
90 .162 .267 .272 .265 .263 .268 .250 .274 .273 .271 .271 
120 .287 .288 .287 .292 .280 .290 .280 .292 .297 .295 .285 
Plot No. Depth in Moisture Content (gig) 
em 6/4172 2014172 2714172 4/5172 1115172 18/5/72 25/5172 1/6172 8/6172 1516172 26/6172 
30 .072 .110 .102 .116 .119 .100 .066 .122 .104 .134 .149 
6 60 .171 .172 .171 .200 .181 .178 .170 .164 .074 .202 .208 
g) .261 .245 .252 .254 .251 .249 .246 .243 .376 .254 .261 
120 .285 .279 .282 .282 .286 .283 .282 .279 .276 .285 .282 
30 .132 .179 .162 .145 .113 .184 .172 .194 .204 
7 60 .199 .218 .199 .211 .181 .246 .245 .246 .234 
g] .224 .216 .227 .226 .224 .252 .249 .268 .254 
1~ .276 .262 .267 .263 .265 .289 .292 .298 .286 
30 .084 .118 .115 .102 .091 .081 .120 .112 .134 .146 
8 60 .175 .171 .183 .168 .175 .163 .157 .155 .168 .213 
g) .232 .229 .239 .225 .231 .228 .220 .225 .233 .235 
120 .256 .253 .255 .252 .258 .253 .248 .251 .258 .247 
30 .160 .164 .142 .124 .113 .159 .186 .203 .204 
9 60 .180 .188 .184 .182 .174 .284 .201 .232 .232 
ro .221 .226 .221 .222 .208 .223 .213 .262 .260 
120 .254 .260 .254 .260 .247 .256 .247 .282 .281 
30 .096 .139 .165 .155 .150 .134 .163 .159 .171 .178 
10 60 .149 .178 .188 .188 .181 .177 .186 .180 .190 .185 
ro ,182 .210 .220 .224 .227 .219 .229 .222 .227 .218 
120 .195 .21' .223 .231 .244 .231 .252 .245 .244 .235 
.0-...\.  
Plot No. Depth in Moisture Content (gIg) ~ 
em 6/4172 20/4/72 ZT /4/72 4/5n2 11/5/72 18/5n2 25/5172 116172 8/6172 15/6/72 26/6172 
30 .069 .093 .084 .106 .090 .083 .082 .099 .088 .097 .102 
11 60 .120 .134 .139 .148 .137 .133 .139 .149 .131 .137 .144 
S(I .206 .208 .207 .216 .210 .215 .215 .227 .207 .214 .204 
720 .197 .198 .197 .208 .200 .211 .208 .218 .206 .212 .195 
30 .068 .107 .076 .115 .000 .073 .053 .106 .109 .112 .120 
12 60 .153 .142 .146 .147 .145 .150 .141 .181 .164 .188 .172 
9J .210 .198 .196 .199 .196 .200 .193 .217 .208 .214 .210 
120 .221 .221 .215 .217 .218 .219 .216 .231 .232 .237 .224 
30 .064 .089 .078 .098 .083 .069 .041 .082 .080 .088 .085 
13 6D .163 .171 .168 .175 .168 .163 .141 .165 .168 .174 .165 
9J .198 .201 .201 .200 .201 .203 .191 .200 .208 .208 .203 
120 .213 .211 .212 .208 .213 .217 .206 .214 .225 .223 .216 
30 .078 .100 .100 .113 .101 .000 .065 .116 .104 .114 .116 
fX) 
14 .152 .161 .169 .159 .159 .148 .14.3 .165 .153 .163 .161 
!XJ .194 .192 .197 .196 .196 .200 .188 .208 .199 .204 .193 
120 .210 .209 .210 .210 .207 .213 .208 .225 .214 .216 .206 
30 .057 .096 .083 .100 .079 .068 .038 .094 .075 .085 .092 
15 60 .110 .122 .128 .124 .110 .104 .087 .132 .115 .111 .125 
ro .173 .165 .168 .163 .163 .170 .154 .162 .161 .157 .167 
120 .231 .225 .225 .226 .221 .227 .219 .216 .208 .209 .227 
Plot No. Depth in Moisture Content (gig) 
an 6/4/72 2014/72 27/4/72 415172 11/5172 1815/72 25/5/72 116172 8/6172 1516172 26/6172 
30 .098 .077 .103 .095 .069 .037 .090 .075 .099 .100 
16 60 .175 .175 .190 .176 .180 .152 .180 .159 .183 .183 
!XJ .205 ~210 .206 .216 .211 .198 .207 .201 .215 .206 
120 .214 .214 .211 .221 .221 .216 .222 .212 .226 .217 
30 .097 .111 .104 .091 .049 .089 .086 .099 .105 
17 60 .164 .169 .165 .167 .147 .154 .150 .165 .167 
!XJ .170 .170 .169 .175 .169 .177 .166 .172 .176 
120 .192 .198 .199 .200 .198 .206 .195 .201 .206 
30 .035 .060 .050 .057 .054 .047 .029 .056 .049 .063 .070 
18 60 .036 .039 .042 .042 .037 .032 .025 .043 .035 .048 .043 
!:lJ .061 .060 .060 .062 .059 .061 .056 .063 .059 .067 .061 
120 .078 .078 .078 .077 .076 .080 .080 .080 .082 .088 .091 
, 
30 .035 ,054 .046 .048 .043 .035 .025 .059 .049 .054 .056 
19 60 .049 .050 .049 .048 .044 .040 .033 .053 .048 .049 .050 
!XJ .057 .055 .054 .055 .053 .050 .040 .045 .050 .052 .066 
120 .063 .061 .061 .060 .060 .060 .048 .050 .055 .055 .071 
30 .033 ,050 .042 .052 .052 .040 .026 .054 .037 .048 .051 
60 .034 .040 .040 .040 .040 .039 
20 .028 .044 .055 .035 .036 
!XJ .043 .044 .045 .044 .046 .045 .036 .042 .041 .040 .064 
120 .055 .056 .056 .054 .058 .057 .051 .050 .050 .048 .060 
$ 
tj 
o 
Plot No. Cepth in Moisture Content (gig) 
em 6/4172 20/4172 27/4172 4/5172 11/5/72 18/5172 25/5172 116/72 8/6/72 15/6/72 26/6/72 
30 .035 .040 .030 .104 .048 .041 .030 .062 .050 .057 .054 
21 60 .043 .039 .040 .040 .041 .043 .040 .064 .055 .061 .056 
90 .054 .042 .043 .038 .041 .043 .042 .062 .060 .061 .056 
120 .050 .042 .039 .040 .039 .040 .040 .061 .054 .059 .053 
30 .046 .071 .058 .071 .067 .052 .038 .030 .066 .068 .073 
22 60 .044 .050 .051 .048 .047 .047 .034 .059 .054 .060 .064 
EX) .046 .046 .048 .048 .045 .044 .036 .055 .049 .054 .063 
120 .065 .065 .066 .071 .065 .058 .056 .076 .069 .074 .077 
30 .031 .051 .043 .050 .052 .044 .025 .053 .039 .049 .058 
23 60 .037 .042 .042 .041 .040 .038 .027 .048 .040 .046 .045 
9J .069 .060 .061 .062 .064 .065 .051 .065 .055 .060 .061 
120 .089 .087 .085 .087 .086 .089 .085 .092 .084 .090 .086 
30 .033 .053 .044 .054 .053 .044 .042 ,057 .050 .052 .054 
60 .030 .042 .042 .045 .045 .042 .038 .OS2 .045 .049 .046 
24 EX) ,042 .046 .048 .053 .052 .049 .051 .049 .046 .050 .052 
120 .066 .070 .072 .072 .076 .077 .075 .083 .075 .028 .079 
Plot No. Depth in Moisture Content (gig) 
em 29/6/72 6/1/72 13/7/12 20/1/72 27/1/72 10/8172 24/8/ 72 31/8172 7/9/72 14/9/72 21/9172 
--- --
30 .212 .214 .215 .197 .188 .166 .144 .199 .192 .202 
60 .244 .244 .252 .240 .239 .239 .231 .239 .252 .252 
1 
~ .282 .281 .284 .274 .277 .276 .273 .272 .282 .286 
120 .303 .303 .312 .300 .301 .304 .297 .296 .203 .310 
30 .143 .121 .113 .107 .088 .078 .081 .131 .150 .157 
2 60 .257 .253 .258 .234 .230 .242 .241 .244 .274 .279 
90 .200 .281 .276 .277 .273 .278 .275 .274 .280 .286 
120 .296 .200 .292 .292 .287 .293 .291 .287 .296 .298 
30 .168 .162 .169 .160 .148 .113 .110 .160 .153 .158 
3 60 .222 .217 .220 .219 .215 .200 .199 .215 .224 .223 
~ .304 .293 .299 .292 .292 .284 .296 .294 .298 .301 
120 .324 .320 .316 .317 .318 .308 .314 .318 .322 .325 
30 .183 .182 .183 .160 .140 .116 .100 .177 .170 .174 
4 60 .199 .199 .207 .188 .112 .179 .182 .208 .210 .216 
00 .184 .179 .187 .282 .273 .277 .277 .282 .292 .288 
120 .290 .286 .289 .2as .280 .278 .277 .276 .286 .286 
30 .169 .170 .169 .144 .117 .074 .071 .137 .133 .144 
5 60 .237 .237 .238 .222 .214 .184 .182 .184 .225 .232 
00 .281 .276 .283 .271 .275 .260 .260 .261 .279 .281 
120 .299 .296 .296 .280 .290 .282 .279 .280 .291 .300 
---..J 
--...J t-.J 
Plot No. Cepth in Moisture Content (gig) 
em 29/6172 617172 1317/72 2011/72 2117/72 10/8112 24/8112 31/8/72 7/9/72 14/9/72 21/9172 
30 .152 .153 .160 .140 .119 .086 .068 .142 .146 .143 
6 60 .224 .218 .224 .210 .198 .1~9 .182 .182 .224 .221 
90 .279 .269 .276 .264 .261 .262 .256 .263 .267 .272 
120 .301 .287 .298 .286 .283 .287 .282 .294 .293 .298 
30 .209 .215 .214 .210 .171 .138 .135 .178 .196 .188 
7 60 .232 .230 .231 .230 .227 .214 .208 .211 .232 .232 
ill .257 .260 .258 .262 .239 .242 .245 .241 .260 .254 
120 .292 .288 •. 288 .292 .280 .277 .277 .272 .289 ,284 
30 .149 .152 .162 .154 .145 .093 .094 .145 .150 ,166 
8 6() .222 .226 .227 .222 .220 .204 .204 .205 .231 .236 
ro .247 .248 .248 .249 .247 .245 .243 .242 .255 .262 
120 .263 .261 .267 .261 .264 .261 .260 .260 .274 .283 
30 .200 .202 .206 .170 .148 .120 .111 .166 .183 .187 
6() 
9 .226 .227 .227 .214 .196 .189 .189 .190 .219 .224 
!J) .259 .262 .266 .255 .246 .238 .237 .237 .255 .267 
'20 .281 .285 .286 .274 .263 .256 .260 .261 .274 .281 
30 .179 .180 .180 .171 .157 .096 .121 .168 .164 .167 
10 60 .190 .1 83 .188 .192 .180 .170 .160 .165 .177 .203 
ro .229 .220 .223 .224 .221 .212 .210 .211 .219 .193 
720 .238 .229 .235 .232 .227 .219 .221 .221 .226 .253 
Plot No. Depth in Moisture Content (g/gl 
em 29/6172 617172 13/7172 20/7/72 2717172 10/8172 24/8/72 3118172 7/9/72 14/9172 2119172 
30 .101 .iOO .099 .093 .083 .071 .070 .097 .098 .102 
11 60 .144 .130 .135 .132 .126 .125 .132 .121 .140 .139 
90 .215 .197 .202 .204 .208 .201 .200 .196 .206 .201 
120 .206 .193 .195 .200 .203 .194 .191 .189 .199 .194 
30 .114 .123 .117 .100 .075 .061 .049 .108 .121 .115 
(JJ 
12 60 .168 .163 .173 .150 .149 .142 .146 .148 .177 .185 
99 .200 .198 .198 .190 .196 .192 .192 .197 ,208 .219 
120 .230 .227 .219 .220 .214 .214 .215 .215 .220 .232 
30 .085 .071 .073 .068 .052 .051 .020 .085 .081 .096 
13 60 .164 .166 .171 .166 .152 .156 .129 .163 .167 .181 
90 .200 .201 .200 .202 .196 .191 .184 .196 .196 .208 
120 .215 .213 .215 .214 .214 .209 .206 .212 .213 .222 
--- . 
30 .115 .119 .121 .122 .107 .075 .063 .112 .116 .118 
14 60 .172 .154 .171 .169 .165 .148 .138 .142 .169 .171 
9J .196 .186 .197 .191 .188 .184 .178 .184 .198 .200 
120 .2.09 .203 .208 .203 .201 .199 .198 .201 .212 .213 
30 .100 .078 .077 .065 .050 .044 .041 .073 .000 .097 
15 60 .129 .110 .106 .101 .097 .099 .100 .093 .140 .135 
00 .170 .165 .t66 .160 .158 .162 .159 .160 .176 .170 
120 .231 .224 .220 .219 .223 .221 .219 .218 .224 .232 
--..J 
W 
ti 
~ 
Plot No. Depth in Moisture Content (g/g) 
em 29/6/72 617/72 1317172 2017172 2711172 1018172 24/8/72 3118172 7/9/72 14/9/72 21/9/72 
30 .103 .100 .101 .087 .071 .057 .049 - .088 .098 .1 03 
16 60 .193 .168 .169 .173 .160 .175 .173 - .169 .194 .202 
90 .212 .201 .202 .204 .201 .201 .202 - .199 .210 .216 
120 .221 .213 .213 .214 .213 .213 .211 - .210 .213 .225 
30 .109 .111 .108 ,096 .092 .076 - .097 .105 .108 
60 .170 .164 .161 .159 .155 .156 - .154 .171 .176 
17 9J .180 .179 .176 .174 .171 .173 - .169 .179 .184 
120 .213 .213 .207 .206 .208 .204 - .20t .212 .219 
30 .068 .070 .068 .051 .044 .039 - .065 .061 .064 
60 .047 .037 .045 .032 .030 .033 - .033 .046 
18 .048 
90 .062 .059 .058 .058 .066 .060 - .055 .070 .065 
120 .091 .090 .091 .089 .087 .000 - .087 .091 .093 
30 .052 .048 .050 .046 .045 .031 - .071 .064 .068 
19 60 .051 .045 .046 .047 .045 .045 - .044 .052 .053 
90 .061 .056 .058 .059 .057 .057 - .055 .061 .063 
120 .071 .067 .068 .068 .067 .067 - .064 .071 .073 
30 .046 .042 .051 .041 .033 .026 - .047 .046 .046 
20 60 .038 .032 .033 .031 .030 .029 - .029 .039 .039 
90 .046 .043 .039 .040 .041 .038 - .039 .048 .049 
120 .060 .057 .053 .060 .056 .050 - .055 .066 .069 
Plot No. Depth in Moisture Content (gIg) 
em 29/6172 617172 1317/72 2017172 27/7/72 10/8172 24/8172 31/8172 7/9/72 14/9172 21/9172 
30 .055 .056 .060 .052 .049 .039 - .054 .056 .060 
21 60 .058 .052 .051 .051 .049 .048 - .047 .057 .058 .055 
!J) .057 .056 .054 .055 .052 .051 - .050 .061 .061 
120 .057 .051 .049 .049 .048 .045 - .045 .055 .055 
30 .071 .074 .073 .061 .060 .042 - .060 .067 .068 
22 60 .060 .060 .068 .061 .052 .042 - .044 .057 .059 .067 
ro .060 .061 .066 .057 .051 .044 - .046 .052 .060 
720 .074 .060 .079 .065 .062 .058 
30 .045 .044 .047 .043 .042 .040 .038 .046 .048 
23 60 .100 .105 .103 .102 .100 .102 .099 .109 .107 
ro .072 .059 .063 .065 .064 .063 .065 .063 .070 
720 .088 .086 .087 .086 .087 .086 .085 .087 .088 
30 .053 .054 .052 .046 .039 .030 .053 . •0 46 .049 
24 60 .044 .045 .048 .042 .041 .039 .036 . •0 43 .043 
00 .055 .056 .058 .056 .054 .049 .049 .054 .055 
120 .080 .079 .081 .079 .079 .074 .071 .077 .078 
5i 
~ 
~ 
Plot No. Depth in Moisture Content Ig/g) 
em 2819172 5/10172 1 2/10 172 19 / 10/72 27/10 / 72 2/11 172 9/ 11172 1 6 / 11/72 30/~ 1/72 14/ 1 2172 28/1 2172 
0.213 0.093 0.070 0.049 0.007 
.?O 0.015 0.002 0.003 0.006 0.015 0.009 
0.144 0.166 0.138 0.117 0.069 0.066 0. 055 0.053 0 .020 0.040 0.039 
0.253 0.199 0.145 0.135 0.085 0.125 0.092 0.081 0.068 0.054 0.082 
60 0.212 0.246 0.186 0.205 0.156 0.156 0.151 0.155 0.130 0.147 0.149 
1 0.285 0.234 -- 0.227 0.231 0.194 0.201 0.186 0.173 0.168 0.164 
90 0.173 
0.238 0.279 0.282 0 .271 0.263 0.254 0.245 0.245 0.229 0.246 0.246 
120 0.306 0.256 0.232 0.243 0.213 0.227 0.214 0. 197 0.193 0.177 0.190 
0.256 0.309 0.296 0.299 0.291 0.285 0.278 0.272 0.270 0.268 0.269 
0.169 0.137 
30 0.098 0.082 0.040 0.028 0.018 0.018 0.010 0.001 0.008 
0.162 0.020 0.087 0.100 0 .042 0.030 0.028 0.028 0.010 0.027 0.01 T 
0.191 O. T1 2 0.084 
 0.068 0.052 
60 0.048 0.045 0.045 0.045 0.044 0.049 
0.282 0.260 0.174 0.237 0.174 0.169 0.171 0.171 0.145 0.183 0.163 
2 
0.236 
90 0.237 0.179 0.220 0.189 0.174 0.171 0.176 0.151 0.123 0.174 
0.289 0.291 0.275 0.266 0.253 0.250 0.251 0.247 0.247 0.244 0.247 
0.254 0.284 
120 0.242 0.241 0.236 0.224 0.215 0.213 0.203 0.198 0.213 
0.302 0.298 0.286 0.358 0.257 0.254 0.249 0.247 0.250 0.249 0.247 
Plot No. Depth in Moisture Content (gig) 
an 28/9/72 5/10/72 12110172 19/1017 2 27/1017 2 2111/72 9/11/72 16/11172 30/11/72 14/1 ?/72 28/12172 
0.171 0.160 0.134 0.150 0.100 0.075 0.067 0.058 0.049 0.036 0.039 
30 
0.164 0.157 0.154 0.152 0.107 0.093 0.091 0.084 0.085 0.067 0.064 
0.169 0.168 0.162 0.157 0.157 0.141 0.136 0.132 0.121 0.113 0.111 
60 0.239 0.227 0.212 0.216 0.186 0.178 0.177 0.166 0.151 0.153 0.148 
3 0.231 0.230 0.212 0.224 0.211 0.204 0.202 0.204 0.189 0.189 0.186 
90 0.308 0.300 0.296 0.292 0.269 0.267 0.273 0.269 0.250 0.258 0.254 
0.311 0.299 0.271 0.291 0.268 0.261 0.262 0.266 0.246 0.253 0.251 
120 0.323 0.319 0.320 0.316 0.316 0.313 0.313 0.307 0.300 0.305 0.301 
30 0.195 0.164 0.138 0.149 0.042 0.020 0.015 0.008 0.009 0.006 0.018 
0.180 0.185 0.175 0.150 0.080 0.067 0.056 0.054 0.039 0.040 0.032 
0.210 0.020 0.133 0.109 0.097 0.087 0.082 0.085 0.087 0.080 0.083 
60 0.139 0.213 0.196 0.189 0.120 0.119 0.112 0.116 0.099 0.115 0.102 
4 
0.289 0.225 0.194 0.206 0.185 0.168 0.164 0.161 0.440 0.166 0.148 
90 0.222 0.296 0.285 0.279 0.250 0.234 0.233 0.233 0.222 0.231 0.230 
0.2B7 0.255 0.251 0.244 0.239 0.239 0.239 0.230 0.223 0.216 0.220 
120 0.269 0.288 0.28Q 0.288 0.281 0.267 0.251 0.248 0.249 0.247 0.246 
0.159 0.121 0.112 0.082 0.033 0.025 0.017 0.017 0.008 O.OlD 0.005 
30 0.161 0.125 0.120 0.087 0.039 0.040 0.032 0.032 0.022 0.019 0.022 
~ 
~ 
-~ 
Plot No. Depth in Moisture Content Ig/g) 
an 2Jj/9n2 5/10/72 1 211 0 /72 1 9/1 0/72 27/1 0/72 2/11/72 9/1 1 172 1 6/11/72 30/1 1172 1 4/1 2172 28/1 2172 
0.233 0,133 0.114 0.110 0.070 0.063 0.060 0.061 0.057 0.059 0.061 
60 0.178 0.215 0.189 0.174 0.116 0.133 0,110 0.137 0.113 0.131 0.123 
5 
0.282 0.252 0.219 0.221 0.179 0.173 0.170 0.174 0.164 0. 166 0.175 
90 0.265 0.282 0.261 0.250 0.218 0.222 0.213 0.223 0.211 0.217 0.216 
0.297 0.276 0.272 0.266 0.247 0.233 0.237 0.238 0.229 0.229 0.239 
120 0.283 0.298 0.308 0.277 0.265 0.264 0.258 0.259 0.254 0.253 0.261 
0.160 0.207 0.155 0.181 0.120 0.095 0.091 0.087 0.073 0.072 0.066 
30 0.222 0.147 • 0.121 0.111 0.073 0.060 0.051 0.039 0,022 0.028 0.023 
0.232 0.170 0.196 0.154 0.138 0.127 0.125 0.126 0.122 0.124 0,119 
60 0.175 0.225 0.192 0.170 0.151 0.135 0.141 0,140 0.123 0.136 0.130 
6 0.275 0.241 0.183 0.240 0.203 0.201 0.189 0.188 0.166 0.187 0.171 
90 0.247 0.269 0.263 0.256 0.246 0.231 0.225 0.225 0.207 0.216 0.211 
0.300 0.280 0.268 0.271 0.277 0.239 0.267 0.032 0.234 0.242 0.232 
120 0.283 0.294 0.295 0.280 0.282 0.273 0.264 0.265 0.244 0.251 0.245 
0.202 0.146 0.130 0.103 0.052 0.042 0.035 0.036 0.026 0.027 0.028 
30 0.195 0.190 0.117 0.178 0.082 0.055 0.044 0.038 0.011 0.027 0.024 
60 0.231 0.157 0.135 0.137 0.102 0.098 0.097 0.096 0.089 0.090 0.097 
0.193 0.225 0.225 0.200 0.188 0.175 0.176 0.175 0.155 0.168 0.169 
7 
Plot No. Depth in Moisture Content (g/gj 
an 213/9/ 72 5/10172 1 2110172 19/1017 2 27/ 1017 2 2/11172 9/11172 16/11 /72 30/11 /72 14/12/72 28/1 2f72 . 
0.256 0.237 0.231 0.230 0.204 0.202 0.196 0.196 0.195 0.191 0.197 
90 0.253 0.261 0.222 0.246 0.221 0.212 0.204 0.202 0.185 0.189 0.192 
0.284 0.282 0.275 0.283 0.254 0.246 0.239 0.236 0.235 0.235 0.236 
120 0.296 0.294 0.266 0.277 0.268 0.266 0.259 0.258 0.233 0.237 0.240 
0.189 0 .173 0.167 0.140 0.092 0.085 0.082 0.078 0.070 0.068 0.072 
30 0.196 0.147 0.140 0.153 0.070 0.051 0.042 0.035 0.024 0.024 0.029 
0.253 0.225 0.181 0.195 0.160 0.155 0.161 0.159 0.145 0.134 0.154 
60 0.244 0.216 0.188 0.188 0.154 0.146 0.143 0.143 0.129 0.132 0.141 
8 
90 0.263 0.240 0.238 0.229 0.212 0.208 0.209 0.204 0.207 0.206 0.207 
0.250 0.253 0.235 0.246 0.212 0.207 0.205 0.205 0.202 0.200 0.202 
0.284 
120 0.277 0.258 0.273 0.252 0.236 0.235 0.234 0.223 0.223 0.231 
0.282 0.275 0.268 0.269 0.251 0.243 0.238 0.233 0.230 0.228 0.232 
30 0.213 0.149 0.118 0.114 0.063 0.054 0.044 0.044 0.036 0.037 0.037 
0. 177 0.162 0.144 0.142 0.081 0.068 0.060 0.056 0.050 0.054 0.053 
0.239 0.168 0.132 0.147 0.110 0.102 0.096 0.098 0.095 0.093 0.095 
60 0.211 0.205 0.172 0.186 0.152 0.149 0.147 0.146 0.138 0.146 0.144 
9 
90 0:1:17 0.254 0.208 0.234 0.187 0.186 0.172 0.183 0.175 0.182 0.179 
0.259 0.251 0.228 0.243 0.201 0.191 0.190 0.188 0.182 0.187 0.185 
-~ 
~ 
Plot No. Depth in Moisture Content Ig/g} 
em 2B19172 5/10/72 12110/72 19/10/7227/10/722/11172 9/11/72 16/11172 30/11/72 14/1l.l72 28/12172 
0.299 0.292 0.282 0.283 0.261 0.251 0.243 0.243 0.241 0.240 0.243 
120 0.294 0.264 0.251 0.272 0.235 0.228 0.221 0.221 0.211 0.223 0.217 
------- .. -
0.180 0.154 0.142 0.174 0.119 0.100 0.093 0.089 0.080 0.079 0.069 
30 0.187 0.163 0.156 0.165 0.127 0.114 0.099 0.098 0.081 0.082 0.073 
60 0.186 0.196 0.191 0.205 0.184 0.175 0.166 0.163 0.150 0.145 0.136 
0.208 0.172 0.179 0.175 0.171 0.166 0.157 0.155 0.140 0.132 0.126 
10 
0.228 0.198 0.195 0.210 0.196 0.190 0.109 0.187 0.178 0.178 0.172 
90 0.198 0.213 0.200 0.217 0.203 0.201 0.199 0.201 0.180 0.183 0.181 
0.239 0.224 0.224 0.268 0.233 0.222 0.220 0.224 0.209 0.215 0.273 
120 0.256 0.233 0.228 0.224 0.233 0.227 0.228 0.228 0.212 0.211 0.209 
0.108 0.090 0.071 0.037 0.037 0.031 0.025 0.021 0.008 0.020 0.011 
30 0.096 0.099 0.102 0.107 0.069 0.063 0.052 0.044 0.035 0.027 0.028 
0.138 0.214 0.186 0.196 0.168 0.174 0.165 0.161 0.142 0.153 0.145 
60 0.217 0.167 0.130 0.143 0.117 0.126 0.114 0.110 0.096 0.081 0.083 
11 
0.203 0.221 0.232 0.216 0.218 0.221 0.236 0.218 0.255 0.206 0.210 
90 0.224 0.209 0.207 0.213 0.227 0.211 0.198 0.197 0.196 0.180 0.185 
0.200 0.231 0.236 0.225 0.224 0.231 0.240 0.225 0.230 0.217 0.219 
120 0.234 0.217 0.202 0.203 0.196 0.209 0.197 0.198 0.196 0.197 0.188 
Plot No. Depth in Moi:oture Content (gig) 
an 2B19172 5/10172 12110/72 19/10/7 2 2711 Q /72 2/11/72 9/11172 16/11/72 30/11 /72 1 411 2172 28/1 2172 
0.119 0.072 0.042 0.034 0.006 0.014 0.020 0.017 - 0.022 -0.029 - 0.020 
30 0.094 0.099 0.064 0.063 0.033 0.029 0.024 0.022 0.(122 0.012 0.015 
0.177 0.183 0.171 0.160 0.136 0.131 0.118 0.128 0.123 0.115 0.194 
60 
0.195 0.167 0.111 0.142 0.117 0.117 0.113 0.111 0.117 0.096 0.106 
12 
0.211 0.195 0.196 0.188 0.177 0.175 0.169 0.170 0.168 0.168 0.170 
90 0.203 0.209 0.180 0.191 0.171 0.169 0.168 0.167 0.169 0.163 0.162 
0.219 0.220 0.215 0.211 0.205 0.200 0.198 0.209 0.181 0.181 0.182 
120 0.224 0.217 0.211 0.208 0.200 0.191 0.195 0.194 0.195 0.186 0.190 
0.097 0.080 0.070 
30 0.084 0.046 0.032 0.025 0.013 0.003 - 0.001 - 0.001 
0.100 0.090 0.079 0.070 0.042 0.030 0.025 0.017 0.006 0.017 0.006 
0.173 0.205 0.174 
60 0.200 0.165 0.161 0.163 0.160 0.142 0.131 0.143 
0.211 0.174 0.150 0.152 0.127 0.123 0.119 0.115 0.106 0.132 0.113 
13 
90 0.204 0.221 0.205 0.219 0.196 0.199 0.194 0.193 0.192 0.189 0.182 
0.224 0.204 0.193 0.195 0.184 0.181 0.176 0. 171 0.168 0.175 0.167 
0.215 0.234 0.235 0.231 0.228 0.228 0.227 0.222 0.213 0.214 O.21S 
120 0.238 0.215 0.210 0.212 0.208 0.197 0.195 0.189 0.192 0.190 0.189 
0.125 0.081 0.041 0.038 - 0.002 - 0.005 - 0.009 - 0.013 - 0.026 - 0.015 - 0.016 
30 0.123 0.098 0.089 0.065 0.036 0.032 0.025 0.023 0.009 0.022 0.015 
&:i 
~ 
i"a""'  
-- --- - -- - - - -- -
Plot No. Depth in Moisture Controt (gig) 
an 'JP./9/72 5/10/72 12110/72 19/1017 2 27/10/72 2/11172 9/11172 16/ 11/72 30/11/72 14/1 2112 28/1 2172 
0.168 0.170 0.114 0.145 0."22 0.121 0.113 0.118 0.088 0.113 0.118 
60 0.183 0.147 0.095 0.127 0.093 0.095 0.092 0.092 0.073 0.093 0.093 
14 
0.196 0.190 0.184 0.181 0.167 0.160 0.156 0.158 0.154 0.154 0.118 
90 0.190 0.195 0.183 0.177 0.169 0.171 0.168 0.167 0.158 0.165 0.164 
0.208 0.188 0.190 0.181 0.181 0.174 0.165 0.164 0.156 0.161 0.164 
720 0.189 0.209 0.208 0.179 0.192 0.189 0.188 0.186 0.180 0.183 0.184 
0.102 0.047 0'.034 0.039 -0.011 -0.017 0.018 0.024 0.030 - 0.040 - 0.033 
30 0.073 0.081 0.079 0.063 0.023 0.018 0.010 0.007 -0.011 0.005 - 0.001 
0.134 0.154 0.110 0.138 0.074 0.073 0.075 0.070 0.060 0.053 0.058 
60 0.164 0.118 0.097 0.097 0.068 0.064 0.058 0.061 0.044 0.060 0.058 
15 
0.166 0.198 0.181 0.194 0.166 0.160 0.163 0.158 0.156 0.155 0.156 
90 0.200 0.164 0.151 0.160 0.135 0.132 0.130 0.130 0.124 0.125 0.128 
0.229 0.212 0.204 0.210 0.200 0.195 0.194 0.188 0.183 0.184 0.185 
120 0.215 0.224 0.203 0.225 0.194 0.193 0.188 0.186 0.175 0.178 0.208 
0.107 0.054 0.054 0.037 0.012 0.006 0.000 - 0.005 - 0.010 - 0.018 - 0.015 
30 0.069 0.096 0.079 0.175 0.056 0.035 0.340 0.020 0.013 0.009 - 0.001 
0.200 0.090 0.067 0.062 0.043 0.043 0.042 0.040 0.036 0.030 0.037 
60 0.107 0.188 0.151 0.207 0.137 0.133 0.127 0.122 0.110 0.111 0.104 
16 
Plot No. Depth in Mol sture Content (g/g) 
em 2819 /72 5/10172 12110172 19 / 10 / 72 27/ 1017 2 2/11172 9/11/n 16/11 172 30 / 11172 1 411 2172 28 / 1 2/72 
0.215 0.164 0.139 0.144 0.105 0.110 0.107 0.108 0.100 0.099 0.101 
90 0.162 0.215 0.206 0.215 0.201 0.198 0.190 0.189 0.178 0.175 0.180 
0.214 0.243 0.224 0.231 0.196 0.199 0.197 0.201 0.193 0.193 0.194 
120 0.245 0.224 0.223 0.237 0.208 0.206 0.201 0.195 0.186 0.179 0.176 
0.110 0.090 0.092 0.101 0.036 0.017 0.005 - 0.002 0.014 -0.015 - 0.019 
30 0.106 0.082 0.071 0.078 0.043 0.036 0.026 0.022 0.009 0.004 0.009 
0.170 0.131 0.121 0.125 0.104 0.094 0.008 0.089 0.078 0.080 0.078 
60 0.144 0.165 0.137 0.129 0.122 0.121 0.118 0.119 0.113 0.112 0.114 
17 
0.180 0.180 0.165 0.188 0.152 0.146 0.144 0.144 0.129 0.113 0.1 2 
90 0.191 0.176 0.166 0.171 0.160 0.151 0.148 0.148 0.146 0.142 0.141 
0.213 0.216 0.210 0.224 0.200 0.200 0.192 O. 191 0.215 0.179 0.179 
120 0.218 0.210 0.197 0.205 0.193 0.183 0.171 0.167 0.164 0.161 0.161 
0.074 0.051 0.035 0.033 0.021 0.020 0.017 0.017 0.014 0.011 0.010 
30 0.057 0.066 0.067 0.061 0.033 0.025 0.020 0.020 0.013 0.013 0.012 
0.049 0.044 0.038 0.048 0.031 0.031 0.033 0.032 0.030 0.029 0.030 
60 0.068 0.042 0.039 0.032 0.028 0.026 0.025 0.026 0.023 0.023 0,023 
18 
0.064 0.082 0.080 0.093 0.074 0.076 0.075 0.077 0.070 0.016 0.074 
90 0.101 0.061 0.053 0.056 0.046 0.046 0.046 0.046 0.041 0.044 0.043 
~ 
-.0.,0.  
Plot No. Depth in Moisture Content (g/g) 
an 2819172 5/10/ 72 12110/72 1 9/1017 2 27/1017 2 2/11/72 9/11/72 16/11/72 30/11 /72 1411 V1Z 28/ 1 2n2 
0.093 0.112 0.112 0.110 0.102 0.101 0.102 0.103 0.099 0.010 0.100 
120 0.119 0.092 0.083 0.080 0.071 0.072 0.071 0.073 0.069 0.069 0.068 
0.052 0.068 0.072 0.069 0.044 0.033 0.032 0.029 0.024 0.026 0.023 
30 0.078 0.045 0.047 0.045 0.014 0.009 0.006 0.006 0.000 - 0.002 0.001 
0.055 0.086 0.076 0.073 0.061 0.055 0.057 0.055 0.053 0.055 0.055 
60 0.090 0.049 0.044 0.040 0.029 0.027 0.026 0.027 0.024 0.024 0.025 
19 
0.063 0.115 0.111 0.112 0.106 0.098 0.100 0.097 0.095 0.095 0.097 
90 
0.117 0.062 0.055 0.052 0.038 0.036 0.036 0.038 0.035 0.036 0.036 
0.072 0.128 0.127 0.126 0.127 0.117 0.115 0.115 0.114 0.114 0.115 
120 0.127 0.067 0.064 0.063 0.046 0.044 0.044 0.046 0.043 0.045 0.044 
0.052 0.051 0.048 0.054 0.028 0.015 ,,' 0.014 0.010 0.007 0.007 0.005 
30 0.056 0.055 0.046 0.042 0.023 0.017 · . 0.015 0.012 0.009 0.007 0.006 
0 .040 0.092 0.059 0.066 0.045 0.039 0.042 0.038 0.037 0.036 0.035 
60 0.093 0.037 0.035 0.028 0.026 0.024 0.023 0.023 0.022 0.022 0.022 
20 0.049 0.125 0.117 0.119 0.109 0. 107 0.108 
9 0.107 0.104 0.105 
0 0,103 
0.125 0.043 0.039 0.040 0.030 0.029 0.027 0.030 0.027 0.031 0.027 
0.063 0.127 0.126 0.126 0.120 0.115 0.115 0.114 0.111 0.115 0.112 
120 0.127 0.057 0.052 0.062 0,040 0.038 0.035 0.037 0.034 0.017 0.036 
Plot No. Depth in Moi sture Content (gig) 
em 28/9172 5/10/ 72 12/1 <1 /72 19/10!7 2 27/ 1017 2 2/11 /72 9/ 11 /72 16/ 11/72 30/ 1 1/72 1 4/1 V72 28/1 2172 
0.059 0.050 0.031 0.032 0.019 0.01 9 0.015 0.015 0.008 0.011 0.010 
30 0.061 0.051 0.043 0.048 0.020 0.015 0.013 0 .011 0.009 0.008 0.006 
0.057 0.081 0.065 0.070 0.059 0.060 0.056 0.058 0.049 0.053 0.055 
60 0.087 0.053 0.051 0.045 0.037 0.035 0.035 0.034 0.033 0.033 0.033 
21 
0.182 0.120 0.105 0.113 0.101 0.102 0.100 0.100 0.092 0.097 0.098 
90 0.119 0.057 0.050 0.045 0.041 0.038 0.037 0.037 0.037 0.037 0.037 
0.056 0.124 0.121 0.123 0.116 0.115 0.111 0.111 0.107 0.111 0.111 
120 0.125 0.053 0.047 0.043 0.037 0.035 0.034 0.034 0.034 0.034 0.034 
0.048 0.083 0.083 0.083 0.059 0.043 0.037 0.037 0.036 0.040 0.027 
30 0.095 0.060 0.026 0.057 0.016 0.011 0.007 0.002 0.001 - 0.004 0.000 
0.064 0.099 0.092 0.086 0.079 0.077 0.072 0.073 0.071 0.070 0.069 
60 0.103 0.047 0.050 0.044 0.040 0.035 0.032 0.030 0.030 0.029 0.029 
22 
0.061 0.117 0.114 0.115 0.105 0.097 0.006 0.094 0.092 0.094 0.088 
90 0.119 0.057 0.044 0.046 0.040 0.038 0.036 0.034 0.033 0.034 0.034 
0.075 0.121 0.120 0.119 0.121 0.119 0.112 0.111 0.108 0.108 0.106 
120 
0.122 0.073 0.059 0.063 0.052 0.051 0.049 0.047 0.042 0.047 0.048 
0.063 0.069 0.050 0.064 0.023 0.021 0.019 0.018 0.014 0.013 0.014 
30 0.076 0.059 0.041 0.052 0.026 0.014 0.011 0.009 0.004 0.003 0.001 
t;; 
VI 
i 
Plot No. Dep1h in Moisture Coat.t(g/g) 
em 28/9172 &/10n2 12110 m 19/1 0/72 27/10/72 2111 n2 91i 1172 18/11172 30/11172 14/1 ZI72 2811 2/72 
60 0.049 0.109 0.095 0.104 0.040 0.079 0.076 0.078 0.069 0.073 0.073 
0.108 0.044 0.040 0.036 0.029 0.026 0.023 0.023 0.022 0.021 0.021 
23 
0.063 0.126 0.119 0.122 0.080 0.106 0.104 0.104 0.100 0.t02 0.104 
90 0.127 0.065 0.047 0.053 0.037 0.035 0.034 0.036 0.034 0.038 0.034 
0.087 0.134 0.'33 0.129 0.109 0.117 0.116 0.116 0.113 0.114 0.115 
'%J 0.136 0.0B9 0.087 0.087 0.076 0~072 0.089 0.010 0.068 0.126 0.068 
0.064 0.071 0.061 0.067 Q.Q.49 0.049 0.034 0.032 0.029 O.O~ 0.024 
30 0.073 0.048 0.038 0.046 0.021 0.018 0.015 0.011 0.006 0.008 ·0.006 
0.047 0.111 0.091 0.108 0.096 0.086 0.091 0.092 0.086 0.086 0.082 
60 0.111 0.043 0.046 0.040 0.042 0.042 0.038 0.036 0.033 0.029 0.028 
24 
0.054 0.124 0.119 0.121 0.117 0.120 0.117 0.116 0.113 0.111 0.112 
90 0.124 0.054 Q041 0.054 0.037 0.037 0.036 0.034 0.028 0.031 0.027 
120 0.019 0.t19 0.131 0.132 0.128 0.133 0.128 0.129 0.127 0.126 0.128 
0.132 0.078 0.074 0.018 0.071 0.072 0.069 0.067 0.062 0.062 O.O~ 
APPENDIX 4b Soil moisture records for 1973 
PI o t N o. Deepmt h in Moisture Content (g) 
27/4/73 30/4/73 7/5173 14/5173 21 / 5/73 28/5/ 73 4/6/73 12/ 6/73 18/ 6/73 ·--25/ 6/73217/73 
30 0.131 0.128 0.148 0.082 0.043 0.053 0.049 0.135 0.108 0.131 0.171 
60 0.192 0.200 0.205 0.186 0.153 0.149 0.145 0.180 
1 0.197 0.182 0.228 
90 0.259 0.261 0.257 0.264 0.264 0.254 0.240 0.244 0.261 0.251 0.287 
120 0.264 0.272 0.272 0.283 0.281 0.283 0.272 0.279 0.285 0.267 0.302 
30 0.144 0.153 0.177 0.082 0.063 0.096 0.079 0.179 0.136 0. 158 0.181 
60 0.147 0.147 0.137 0.098 0.083 0.092 0.079 0.154 0.132 0.140 0.160 
2 90 0.158 0.267 0.272 0.262 0.252 0.259 0.251 0.283 0.278 0.259 0.252 
720 0.257 0.263 0.274 0.275 0.270 0.275 0.274 0.291 0.296 0.288 0.282 
--_ ._. . _-
30 0.123 0.132 0.150 0.138 0.115 0.124 0.133 0.165 0.150 0.142 0.163 
60 0.154 0.152 0.158 0.161 0.165 0.158 0.161 0.168 0.167 0. 158 0.161 
3 90 0.232 0.233 0 .238 0.243 0.250 0.249 0.247 0.253 0.250 0.236 0.233 
120 0.293 0.297 0.300 0.309 0.315 0.307 0.316 0.334 0.319 0.311 0.303 
30 0.105 0.117 0.147 0.082 0.047 0.055 0.066 0.157 0.124 0.120 0.143 
60 0.178 0.173 0.152 0.130 0.104 0.111 0.102 0.163 0.154 0.170 0.185 
4 90 0.237 0.247 0.239 0.243 0.233 0.224 0.222 0.247 0.251 0.230 0.238 
120 0.285 0.290 0.277 0.286 0.278 0.282 0.271 0.292 0.296 0.275 0.280 
~ 
-~ 
Moisture Content (g)_.- -
Plot No. D~h in 
27/ 4/73 30/4/73 7/5173 14/5/73 2115/73 28/5173 4/6173 121G/73 18 /6173 25/6/73 V7173 
30 0.136 0.154 0.165 0.078 0.064 0.087 0.082 0.175 0.142 0.163 0.210 
5 60 0.183 0.194 0.185 0.133 0.118 0.116 0.118 0.200 0.175 0.180 0.263 
90 0.252 0.279 0.277 0.280 0.256 0.240 0.249 0.291 0.282 0.256 0.320 
120 0.Z2 0.306 0.309 0.308 0.314 0.299 0.292 0.329 0.317 0.298 0.362 
. -. - ~ ..- 
30 0.194 0.201 0.188 0.142 0.125 0.130 0.133 0.213 0.148 0.205 0.221 
6 60 0.209 0.205 0.191 0.174 0.164 0.163 0.158 0.201 0.229 0.198 0.213 
90 0.263 0.256 0.264 0.213 0.253 0.252 0.235 0.242 0.305 0.232 0.255 
120 0.292 0.301 0.302 0.308 0.314 0.298 0.297 0.291 0.327 0.280 0.311 
30 0.197 0.202 0.191 0.132 0.091 0.097 0.098 0.189 0.180 0.188 0.207 
7 60 0.215 0.209 0.199 0.170 0.150 0.157 0.155 0.179 0.201 0.182 0.202 
90 0.279 0.278 0.278 0.281 0.262 0.258 0.253 0.251 0.266 0.249 0.259 
120 0.309 0.314 0.314 0.315 0.311 0.298 0.292 0.293 0.299 0.269 0.286 
-- --
30 0.187 0.173 0.197 0.127 0.120 0.132 0.125 0. 195 0.163 0.192 0.200 
8 60 0.262 0.264 0.256 0.211 0.224 0.219 0.221 0.268 0.253 0.285 0.253 
90 0.260 0.275 0.268 0.256 0.257 0.247 0.243 0.272 0.267 0.262 0.268 
120 0.281 0.294 0.285 0.273 0.299 0.288 0.284 0.296 0.296 0.285 0.294 
30 0.169 0.154 0.182 0.118 0.106 0.131 0.130 0.195 0.187 0.184 0.189 
9 60 0.207 0.210 0.195 0.168 0.163 0.155 0.160 0.231 0.204 0.215 0.220 
90 0.276 0.280 0.270 0.261 0.268 0.239 0.256 0.290 0.261 0.273 0.264 
120 0.296 0.306 0.293 0.290 0.297 0.283 0.287 0.311 0.282 0.303 0.312 
Moi stur onte nt (g) 
Plot No. D~h e C
in 
21 14/73 30/4173 7/5173 14/5/73 21/5/73 28/5/73 4/6/73 12/6/13 18/ 6/73 25/6/73 2/7/73 
30 0.159 0.182 0.1 97 0.156 0.161 0.177 0.175 0.206 0.186 0.178 0.189 
60 0.192 0.201 0.200 0. 196 0.199 0.204 0.198 0.201 0.215 0.204 0.212 
10 90 0.208 0.210 0.211 0.210 0.221 0.216 0.221 0.219 0.220 0.201 0.212 
120 0.244 0.258 0.252 0.256 0.264 0.261 0.260 0.263 0.266 0.235 0.237 
30 0.080 0.089 0.128 0.083 0.075 0.094 0.096 0.118 0.100 0.053 0.103 
11 60 0.210 0.224 0.227 0.220 0.211 0.208 0.216 0.232 0.231 0.162 0.218 
90 0.240 0.244 0.247 0.240 0.238 0.233 0.238 0.245 0.246 0.244 0.241 
120 0.239 0.238 0.247 0.242 0.239 0.236 0.240 0.253 0.253 0.245 0.249 
3n ' 094 0.099 0.084 0.047 0.040 0.059 0.051 0.120 0.102 0.098 0.116 
12 60 0.216 0.220 0.209 0.208 0.189 0.191 0.190 0.222 0.217 0.199 0.212 
90 0.231 0.238 0.231 0.235 0.225 0.225 0.223 0.237 0.231 0.212 0.229 
120 0.244 0.249 0.244 0.250 0.247 0.245 0.243 0.253 0.250 0.227 0.210 
30 0.083 0.080 0.089 0.033 0.023 0.043 0.037 0.100 0.085 0.088 0.114 
13 60 0.218 0.224 0.217 0.165 0.183 0.181 0.181 0.221 0.214 0.205 0.248 
90 0.228 0.236 0.230 0.219 0.226 0.214 0.219 0.235 0.241 0.221 0.265 
120 0.250 0.254 0.249 0.252 0.248 0.243 0.229 0.247 0.245 0.245 0.293 
30 0.080 0.081 0.092 0.044 0.029 0.059 0.054 0.103 0.097 0.104 0.097 
14 60 0.193 0.195 0.187 0.187 0.173 0.180 0.175 0.206 0.203 0.203 0.192 
90 0.216 0.226 0.220 0.223 0.217 0.209 0.199 0.203 0.219 0.225 0.218 
120 0.208 0.219 0.217 0.226 0.224 0.220 0.214 0.215 0.217 0.224 0..269 
i 
~ 
Mol sture Conte nt. (9) 
PI o t N o. Deepmth  in 
27/ 4/ 73 3014/ 73 7/ 5/ 13 14/ 5/73 21/5173 28 / 5/73 416/73 12/6173 18 / 6173 25/6/73 2/7173 
30 0.047 0.046 0.047 0.012 0.001 0.010 0.020 0.073 0.044 0.058 0.068 
60 0.148 0.159 0.146 0.122 0.117 0.107 0.127 0.162 0.156 0.142 0.148 
1S 90 0.219 0.224 0.214 0.226 0.205 0.199 0.202 0.209 0.215 0.198 0.210 
120 0.234 0.237 0.234 0.247 0.241 0.236 0.235 0.234 0.236 0.222 0.234 
30 O.om 0.065 0.074 0.024 0.007 0.108 0.013 0.073 0.043 0.073 0.084 
16 60 0.113 0.115 0.102 0.079 0.063 0.058 0.066 0.083 0.079 0.073 0.107 
90 0.160 0.170 0.170 0.172 0.157 0.148 0.145 0.146 0.146 0.126 0.113 
120 0.230 0.230 0.226 0.170 0.238 0.238 0.144 0.150 0.228 0.222 0.154 
30 0.084 0.102 0,090 0.053 0.029 0.038 0.044 0.101 0.075 0.078 0.096 
17 60 0.154 0.162 0.152 0.126 0 .117 0.111 0.113 0 .125 0.124 0.112 0.132 
90 0.196 0.208 0.193 0.195 0.100 0.172 0.180 0.175 0.180 0.159 0.166 
120 0.217 0.229 0.219 0.226 0.224 0.212 0.218 0.219 0.219 0.206 0.209 
30 0.057 0.052 0.043 0.031 0.027 0.027 0.029 0.037 0.Q32 0.020 0.036 
18 60 0.060 0.061 0.061 0.069 0.045 0.046 0.048 0.045 0.047 0.022 0.039 
90 0.094 0.098 0.105 0.114 0.098 0.102 0.099 0.096 0.100 0.057 0.084 
120 0.115 0.118 0.122 0.124 0.124 0.123 0.120 0.119 0.123 0.078 0.113 
-
30 0.079 0.069 0.075 0 .0 48 0.040 0.049 0.045 0.074 0.064 0.073 0.080 
60 0.096 0.090 0.093 0.075 0.071 0.072 0.072 0.098 0,094 0.088 0.094 
19 
Depth in Moisture Conl rmt [g) 
Plot No. em 271411-3 -30~/4-1-7-3- :--7~1-5-/7:3- -::1~4/-5-1:1:32 -=-1/-;:5-/-;7=-:3-:--2~-8=-/-;:5:-/:=7-3=---4i6173 - i2/ 6I ii- '1S-I-S-/ 7-3--ZS-I-S-n-3--V- 7' /73 
90 0.126 0.124 0.130 0.124 0.119 0.116 0.114 0.126 0.123 0.122 0.127 
120 0.112 0.133 0.134 0.135 0.137 0.1'31 0.126 0.134 0.137 0.134 0.137 
.... _-.--- ----------
30 0.057 0.045 0.047 0.025 0.018 0.026 0.026 0.053 0.046 0.046 0.052 
60 0.078 0.076 0.080 0.084 0.065 0.053 0.063 0.085 0,084 0.072 0,019 
20 
90 0.134 0.130 0.135 0.139 0.133 0.132 0.130 0.136 0.138 0.129 0.132 
120 0.138 0.137 0.139 0.145 0.144 0.138 0.138 0.140 0.141 0.138 0.141 
30 0,063 0.053 0.052 0 .028 0.029 0,036 0.032 0.057 0.051 0.048 0,064 
21 60 0.097 0.095 0.086 0.075 0.078 0.078 0.078 0.096 0.091 0.089 0.092 
90 0.130 0.127 0.128 0. 1:1) 0.125 0.126 0.125 0.127 0.131 0.122 0.124 
120 0.138 0.137 0.135 0.141 0.141 0.140 0. 139 0.058 0.139 0. 135 0.135 
30 0.095 0.091 0.090 0.081 0.065 0.069 0.073 0.101 0.094 0 .094 0.098 
0,109 0.110 0.110 0.105 0.094 0 .092 0.093 0.114 
22 60 0.110 0.110 0.114 
90 0.113 0.118 0.123 0.126 0.126 0.118 0.115 0.129 0. 128 0.120 D.123 
120 0.123 0.126 0.130 0.133 0.136 0.133 0.130 0.136 0.136 0.131 0.134 
30 0.080 0.067 0.059 0.052 0.042 0.050 0.051 0.076 0.056 0.060 0.061 
60 0.110 0.109 0.108 0.106 0.097 0.099 0.099 0.098 0.098 0.090 
23 0.086 
90 0.128 0.126 0.127 0.129 O. t27 0.127 0.124 0.126 0.1;23 0.119 0.117 
120 0.133 0.133 0.132 0.132 0.135 0.135 0.133 0.134 0.134 0.131 0.155 
tiS 
1-6 
~ 
oisture CO:ltent (g) 
Plot No. D~h M
in 
27/4/73 30/ 4/73 1/ 5173 14/ 5/73 21 / 5173 28/5/73 4/6/ 73 1216/73 18 / 6173 25 /6/73 217173 
30 0.073 0.064 0075 0.060 0.055 0.063 0,068 0.076 0.06B 0.070 0.003 
24 60 0.111 0.109 0.115 0.105 0.113 0.113 0.1'4 0.117 0.116 0.110 0.106 
90 0.130 0.128 0.135 0.134 0.132 0.,,33 0.132 0.132 0.132 0.132 0.127 
120 0.134 0.133 0.138 0.140 0.139 0.138 0.138 0.140 0.141 0.143 0.138 
PI t N Depth in Moisture Content (g) 
o o. em 
9/7/73 1617173 23/7/73 30/7/73 7/8/73 13/8/73 20/8/73 27/8173 3/9/73 10/ 9/73 26/9/73 
30 0.116 0. 124 0.145 0.139 0.145 0.164 0.158 0.169 0.190 0.171 0 .191 
60 0. 174 0. 186 0.199 0.200 0.199 0.195 0.187 0.201 0.213 0.202 0.229 
1 
90 0.253 0.254 0.261 0.262 0.261 0.263 0.262 0.270 0.268 0. 264 0.277 
720 0.257 0.265 0.355 0.268 0.355 0.268 0.270 0.270 0.275 0.268 0.293 
__•  _ _____ _ •• 0 _ _ . _ ••• ____ _ _ .._ ____ . _ 
3D 0.147 0. 152 0.174 0.166 0.174 0.177 0.154 0.166 0.200 0.179 0.188 
60 0.136 0.149 0.161 0.160 0.161 0.166 0.154 0.156 0.167 0. 148 0.135 
2 
90 0.245 0.255 0.262 0.274 0.262 0.276 0.267 0.267 0.278 0.272 0.292 
720 0.285 0.288 0.289 0.294 0.288 0.299 0.287 0.282 0.312 0.287 0.312 
I 
~ ........ ... _- -.---_. . _ .. _-
30 0.135 0.143 0.141 0.139 0.141 0.143 0. 137 0.152 0.177 0.166 0.185 
60 0.172 0.176 0.171 0.172 0.171 0.185 0.177 0.177 0.189 0.193 0.197 
3 90 0.232 0.241 0.251 0.251 0.251 0.252 0.257 0.252 0.246 0.261 0.275 
120 0.309 0.312 0.350 0.315 0.350 0.334 0.321 0.326 0.318 0.333 0.352 
11 0.089 0.103 0.138 0.122 0.138 0.123 0.128 0.135 0.165 0.137 0.177 
4 60 0.166 0.159 0.183 0.178 0.183- 0.181 0.182 0.187 0.197 0.185 0.188 
90 0.230 0.236 0.241 0.232 0.241 0.241 0.240 0.243 0.253 0.242 0.264 
120 0.281 0.288 0.319 0.285 0.319 0.293 0.287 0.291 0.316 0.293 0.320 
~ 
I",J 
i 
PI t N Depth in Moi sture Content (g) 
o o. em 
9/7173 1617/73 2317/73 30/7173 7/8/73 13/8/73 20/8173 27/8173 3/9/73 10/9173 26/9173 
30 0.139 0.132 0.163 0.141 0.163 0.159 0.148 0.164 0.196 0.170 0.182 
5 60 0.169 0.163 0.196 0.154 0.196 0.197 0.190 0.195 0.209 0.197 0.171 
90 0.256 0.260 0.325 0.264 0.325 0.291 0.282 0.285 0.298 0.288 0.305 
120 0.298 0.296 0.329 0.311 0.329 0.322 0.318 0.312 0.323 0.322 0.339 
30 0.186 0.203 0.226 0.212 0.226 0.22' 0.224 0.219 0.245 0.229 0.247 
60 0.192 0.203 0.217 0.232 G.217 0.214 0.210 0.209 0.217 0.212 0.219 
6 90 0.240 0.242 0.246 0.249 0.246 0.263 0.246 0.252 0.256 0.256 0.279 
120 0.296 0.3)1 0.321 0.31a 0.321 0.320 0.315 0.316 0.315 0.317 0.330 
30 0.175 0.185 0.197 0.186 0.197 0.197 0.201 0.209 0.226 0.210 0.23:> 
60 0.191 0.194 0.~1 0.193 0.201 0.220 0.197 0.216 0.225 0.208 0.23J 
7 90 0.269 0.274 0.272 0.270 0.272 0.278 0.270 0.284 0.287 0.280 0.289 
120 0.307 0.319 0.3J8 0.3)9 0.318 0.321 0.318 0.328 0.324 0.321 0.336 
30 0.172 0.178 0.204 0.198 0.204 0.202 0.196 0.195 0.219 0.206 0.218 
8 60 0.236 0.246 0.262 0.249 0.262 0.262 0.255 0.261 0.280 0.267 0.270 
90 0.302 0.259 0.275 0.275 0.275 0.269 0.263 0.263 0.280 0.271 0.282 
120 0.302 0.293 0.306 0.299 0.305 0.302 0.296 0.295 0.308 0.304 0.310 
PI N Depth in Moisture Content (g) 
ot O. em 
9/7/73 16/7/73 2317173 30/7/73 7/8/73 1318/73 20/8/73 27/8/73 3/9/73 10/9/73 26/9/73 
30 0.160 0.162 0.195 0.180 0.195 0.185 0.175 0.178 0.204 0.187 0.209 
60 0.207 0.203 0.218 0.206 0.218 0.220 0.212 0.218 0.231 0.219 
9 0.234 
90 0.278 0.277 0.284 0.274 0.284 0.284 0.277 0.281 0.294 0.284 0.302 
120 0.317 0.295 0.320 0.312 0.320 0.323 0.324 0.322 0.322 0.321 0.332 
-- "_ .. _--
30 0.165 0.160 0.173 0.160 0.173 0.175 0.168 0.182 0.214 0.192 0.208 
60 0.213 0.210 0.190 0.211 0.199 0.218 0.202 0.220 0.231 0.226 0.235 
10 
90 0.227 0.223 0.223 0.220 0.223 0.232 0.218 0.225 0.232 0.236 0.240 
720 0.256 0.264 0.251 0.255 0.251 0.275 0.264 0.269 0.274 0.278 0.280 
30 0.080 0.081 0.066 0.087 0.066 0.088 0.083 0.100 0.124 0.107 0.127 
60 0.205 0.206 0.202 0.219 0.202 0.208 0.212 0.221 0.230 0.221 0.239 
11 
90 0.244 0.2':f1 0.239 0.248 0.239 0.238 0.224 0.248 0.246 0.245 0.250 
120 0.244 0.241 0.240 0.256 0.240 0.250 0.245 0.250 0.254 0.253 0.258 
30 0.090 0.104 0.082 0.123 0.082 0.122 0.128 0.127 0.149 0.133 0.159 
60 0.210 0.210 0.194 0.209 0.194 0.217 0.211 0.213 0.223 0.216 
12 0.227 
90 0.228 0.225 0.212 0.216 0.212 0.224 0.225 0.217 0.225 0.225 0.229 
120 0.244 0.242 0.236 0.237 0.236 0.253 0.250 0.244 0.258 0.251 0.262 
30 0.081 0.078 0.058 0.091 0.102 0.091 0.094 0.096 0.116 0.102 0.120 
60 0.201 O.~ 0.191 0.210 0.212 0.217 0.211 0.214 0.221 0.221 0.237 
13 
~ 
-~ 
Moi sture Conte nt (9) 
Plot No. D~h in 
9/7/73 16/7173 23/7/73 30/7/73 7/8/73 13/8/73 20/8/73 27/8/73 3/9/73 10/9/73 26/9173 
90 0.226 0.221 0.221 0.229 0.223 0.223 0.227 0.227 0.230 0.229 0.255 
720 0.249 0.249 0.238 0.252 0.247 0.257 0.249 0.247 0.251 0.252 0.264 
30 0.088 0.077 0.038 0.080 0.106 0.073 0.065 0.080 0.105 0.086 0.115 
'10 0.195 0.192 0.175 0.186 0.199 0.202 0.191 0.201 0.199 0.188 0.211 
14 90 0.219 0.217 0.209 0.217 0.225 0.219 0.216 0.221 0.212 0.217 0.234 
120 0.221 0.221 0.214 0.221 0.239 0.224 0.222 0.223 0.247 0.223 0.236 
30 0.040 0.057 0.033 0.059 0.081 0.073 0.067 0.073 0.093 0.075 0.097 
15 60 0.139 0.154 0.132 0.151 0.162 0.158 0.149 0.155 0.165 0.163 0.175 
90 0.209 0.226 0.206 0.215 0.221 0.223 0.213 0.162 0.215 0.218 0.231 
120 0.229 0.251 0.230 0.234 0.268 0.243 0.232 0.231 0.227 0.236 0.247 
30 0.056 0.061 0.046 0.073 0.088 0.081 0.075 0.078 0.103 0.086 0.101 
60 0.096 0.100 0.094 0.10B 0.126 0.119 0.113 0.114 0.132 0.116 0.133 
16 90 0.151 0.158 0.156 0.165 0.183 0.169 0.171' 0.169 0.175 0.171 0.191 
720 0.226 0.231 0.234 0.240 0.277 0.250 0.247 0.248 0.250 0.247 0.263 
-----_ ... _----
30 0.068 0.070 0.058 0.093 0.103 0.081 0.087 0.096 0.122 0.103 0.124 
60 0.145 0.140 0.128 0.149 0.158 0.154 0.147 0.157 
17 0.165 0.156 0.164 
90 0.186 0.179 0.177 0.191 0.192 0.189 0.189 0.193 0.193 0.191 0.213 
120 0.221 0.214 0.219 0.2~6 0.231 0.226 0.225 0.232 0.231 0.235 0.246 
----..- ---- -_.. _---_.-
Moisture Content (g) 
Plot No. D~h in 
917173 1617173 2317/73 30/7173 7/8/73 13/8/73 20/8/73 27/8173 319/73 10/9173 26/9/73 
30 0.034 0.032 0.027 0.041 0.064 0.053 0.053 0.055 0.069 0.060 0.062 
18 60 0.044 0.0"45 0.042 0.043 0.063 0.062 0.058 0.062 0.068 0.063 0.059 
90 0.054 0.088 0.088 0.089 0.102 0.103 0.101 0.101 0.103 0.106 0.110 
120 0.089 0.117 0.118 0.118 0.127 0.124 0.124 0.128 0.124 0.128 0.128 
- - ...~ . 
30 0.064 0.067 0.057 0.074 0.076 0.072 0.071 0.073 0.086 0.078 0.084 
60 0.088 0.087 0.084 0.102 0.099 0.096 0.093 0.096 0.102 O. 98 0.104 
19 
90 0.119 0.123 0.121 0.126 0.125 0.122 0.123 0.121 0.120 0.126 0.129 
720 0.132 0.131 0.134 0.138 0.134 0.132 0.134 0.129 0.128 0.135 0.138 
30 0.042 0.045 0.036 0.050 0.061 0.049 0.047 0.051 0.064 0.056 0.068 
20 60 0.069 0.072 0.061 0.075 0.075 0.077 0.073 0.074 0.084 0.079 0.091 
90 0.129 0.130 0.126 0.133 0.130 0.132 0.129 0.129 0.134 0.132 0.140 
120 0.137 0.139 0.137 0.141 0.136 0.139 0.136 0.136 0.140 0.139 0.145 
------ - _._ ... 
30 0.048 0.045 0.036 0.036 0.064 0.058 0.052 0.050 0.065 0.058 0.068 
60 0.089 0.089 0.080 0.094 0.098 0.093 0.093 0.095 0.101 0.099 0.101 
21 
90 0.125 0.124 0.121 0.126 0.126 0.125 0.126 0.126 0.133 0.131 0.135 
720 0.1'34 0.134 0.131 0.134 0.136 0.131 0.137 0.137 0.140 0.138 0.140 
5 
I-' 
~ 
PI N Depth in Moi sture Content (g) 
ot o. em 
9/7/73 16/7/73 23/7/73 30/7/73 7/8/73 13/B/73 20/8/73 27/8/73 3/9173 10/9173 26/9173 
30 0.092 0.093 0.079 0.096 0.102 0.099 0.091 0.097 0.106 0.100 0. 104 
60 0.111 0.113 0.108 0.116 0.117 0.117 0.115 0.115 0.118 0.115 0.113 
22 
90 0.121 0.120 0.117 0.127 0.126 0.126 0.123 0.126 0.126 0.125 0.130 
120 0.1 33 0.133 0.129 0.1'36 0.134 0.137 0.133 0.135 0.134 0.134 0.139 
30 0.046 0.044 0.039 0.052 0.083 0.075 0.075 0.077 0.090 0.083 0.084 
23 60 0.088 0.088 0.090 0.090 0.113 0.111 0.108 0.109 0.117 0.114 0.111 
90 0.118 0.117 0.118 0.118 0.130 0.128 0.130 0.129 0.134 0.132 0.136 
120 0.129 0.1 28 0. 130 0.131 0.138 0.140 0.138 0.139 0.142 0.139 0.142 
30 0.056 0.057 0.050 0.060 0.068 0.060 0.060 0.063 0.075 0.070 0.077 
24 60 0.106 0.107 0.105 0.108 0.107 0.109 0.106 0.108 0.111 0. '10 0.116 
90 0.130 0.1 29 0.128 0.130 0.129 0.132 0.128 0.125 0.131 0.131 0.133 
120 0.121 0.137 0.139 0.139 0.140 0.139 0.137 0.138 0.141 0.142 0.143 
------ ---. 
Plot No. Depth in Moisture Content (9) 
em 3/10/73 8/10173 15/10113 31/10173 1111173 14/11/73 28111173 18/12/73 
30 0.185 0.174 0.160 0.194 0.139 0.087 0.062 0.062 
1 60 0.217 0.204 0.169 0.231 0.186 0.158 0.156 0.149 
9J 0.2 63 0.265 0.25g 0.273 0.264 0.255 0.249 0.240 
120 0.293 0.289 0.282 0.427 0.285 0.287 0.277 
- 0.257 
30 0.186 0.175 0.143 0.197 0.154 0.112 0.088 0.087 
2 60 0.142 0.120 0.097 0.123 0.112 0.094 0.088 0.089 
9J 0.288 0.273 0.261 0.251 0.249 0.251 0.250 0.246 
120 0.299 0.296 0.296 0.2BB 0.287 0.289 0.285 0.280 
30 0.176 0.174 0.162 0.189 0.137 0.132 0.110 0.108 
60 0.199 0.199 0.184 0.189 0.189 0.184 0.166 0.163 
3 9J 0.277 0.278 0.276 0.272 0.271 0.271 0.272 0.258 
720 0.344 0.352 0.338 0.367 0.333 0.336 0.331 0.332 
30 0.170 0.154 0.133 0.186 0.139 0.128 0.064 0.049 
4 60 0.162 0.139 0.120 0.188 0.155 0.157 0.118 0.101 
ro 0.258 0.246 0.232 0.261 0.288 0.236 0.234 0.220 
720 0.302 0.295 0.280 0.317 0.263 0.275 0.269 0.263 
30 0.167 0.125 0.107 0.146 0.105 0.093 0.067 0.077 
5 ro 0.159 0.138 0.115 0.123 0.115 0.120 0.117 0.121 
ro 0.301 0.282 0.263 0.255 0.249 0.253 0.252 0.257 
120 0.338 0.333 0.323 0.327 0.315 0.324 0.315 0.319 
~ 
8
Plot No. Depth in Moi sture Content  
(g) 
-
em 3/10/73 8/10/73 15/10/73 31/10/73 7111/73 14/11/73 28/11/73 18/12/73 
30 0.251 0.232 0.236 0.252 0.222 0.198 0.157 0.139 
6 60 0.216 0.195 0.186 0.220 0.205 0.195 0.175 0.168 
90 0.279 0.270 0.269 0.268 0.274 0.260 0.244 0.249 
120 0.330 0.325 0.320 0.300 0.312 0.293 0.276 0.276 
30 0.225 0.198 0.172 0.261 0.178 0.150 0.125 0.106 
7 60 0.229 0.205 0.180 0.229 0.196 0.180 0.212 0.168 
9J 0.292 0.278 0.273 C.280 0.268 0.270 0.388 0.265 
120 0.332 0.325 0.323 0.293 0.304 0.311 0.442 0,300 
30 0.217 0.211 0.212 0.231 0.198 0.185 0.168 0.167 
S 60 0.269 0.258 0_248 0.282 0.263 Q.261 0.254 0.256 
90 0.279 0.280 0.274 0.295 0.275 0.274 0.267 0.275 
120 0.311 0.317 0.306 0.320 0.309 0.313 0.306 0.306 
30 0.205 0.197 0.177 0.236 0.175 0.152 0.118 0.110 
9 60 0.223 0.203 0.177 0.236 0.205 0.193 0.182 0.169 
9J 0.299 0.291 0.279 0.265 0.274 0 .285 0.275 0.271 
120 0.331 0.334 0.325 0.280 0.311 0.324 0.321 0.31 0 
30 0.215 0.213 0.209 0.183 0.178 0.166 0.153 0.126 
10 60 0.233 0.239 0.230 0.21 0 0.219 0.213 0.201 0.180 
90 0.242 0.250 0.238 0.204 0.239 0.239 0.240 0.230 
120 0.288 0.292 0.289 0.244 0.283 0.283 0.285 0.276 
Plot No. Depth in Moi sture Content (9) 
an 3/10173 8/10/73 15/10/73 31110173 7/11/73 14/11/73 2B/l1/73 18/12/73 
30 0.122 0.114 0.115 0.100 0.103 0.111 0.080 .0.053 
11 60 0.231 0.228 0.229 0.189 0.225 0.255 0.216 0.189 
90 0.253 0.246 0.250 0.200 0.243 0.281 0.243 0.232 
120 0.257 0.258 0,256 0.206 0.253 0.292 0.253 0.240 
30 0.150 0.132 0.137 0.167 0.102 0.083 0.075 0.056 
60 0.226 0.223 0.219 0.226 0.213 0.204 0.199 
'2 0.185 
m 0.228 0.230 0.230 0.232 0.231 0.224 0.217 0.204 
120 0.261 0.259 0.255 0.258 0.260 0.264 0.249 0.237 
30 0.118 0.106. 0.113 0.125 0.1 00 0.072 0.049 0.028 
13 60 0.236 0.213 0.21 0 0.225 0.21 5 0.209 0.197 0.170 
!XJ 0.252 0.239 0.234 0.239 0.226 0.229 0.221 0.200 
120 0.259 0.255 0.255 0.242 0.234 0.237 0.230 0.21 B 
30 0.108 0.087 0.081 0.123 0.053 0.039 0.032 0.014 
14 60 0.205 0.191 0.179 0.202 0.179 0.172 0.172 0.147 
~ 0.225 0.227 0.220 0.213 0.222 0.203 0.207 0.191 
120 0.228 0.227 0.231 0.215 0.230 0.223 0.217 0.203 
30 0.092 0.082 0.071 0.099 0.057 0.036 0.023 0.011 
15 60 0.179 0.163 0.131 0.177 0.143 0.136 0.135 0.1 02 
90 U.230 0.223 0.205 0.220 0.208 0.217 0.211 0.194 
120 0.246 0.241 0.232 0.234 0.240 0.249 0.240 0.225 
~....  
~ 
Plot No. Depth in Moisture Content (9) 
em 3/10/73 8/10/73 15/10173 31/10/73 7/11173 14/11/73 28/11/73 18/12/73 
30 0.096 0.091 0.100 0.111 0.068 0.039 0.017 0.004 
16 60 0.120 0.1 02 0.105 0.134 0.121 0.108 0.080 0.053 
90 0.184 0.181 0.169 0.185 0.184 0.187 0.176 0.130 
120 0.263 0.262 0.247 0.256 0.259 0.261 0.259 0.232 
30 0.127 0.120 0.124 0.136 0.106 0.080 0.045 0.018 
17 60 0.174 0.152 0.153 0.165 0.161 0.156 0.130 0.104 
90 0.221 0.205 0.196 0.203 0.207 0.208 0.194 0.162 
120 0.264 0.248 0.245 0.238 0.245 0.246 0.237 0.212 
30 0.060 0.056 0.055 0.069 0.021 0.034 0.026 0.026 
18 60 0.058 0.056 0.053 0.073 0.337 0.054 0.048 0.043 
9J 0.102 0.100 0.102 0.109 0.280 0.1 06 0.1 00 0.094 
120 0.124 0.122 0.123 0.124 0.015 0.123 0.122 0.117 
- --.-
30 0.087 0.083 0.084 0.090 0.008 0.067 0.051 0.042 
19 60 0.1 04 0.092 0.091 0.107 0.113 0.097 0.089 0.071 
00 0.130 0.124 0.120 0.133 0.130 0.125 0.126 0.110 
120 0.138 0.136 0.131 0.1 'II 0.136 0.131 0.133 0.125 
30 0.067 0.059 0.062 O.Q72 0.053 0.037 0.022 0.022 
20 60 0.086 0.081 ('I.079 0.091 0.083 0.084 0.038 0.061 
EX) 0.139 0.138 0.137 0.138 0.135 0.138 0.132 0.127 
120 0.143 0.141 0.139 0.143 0.138 0.140 0.135 0.133 
Plot No. Depth in Moisture Contellt (9i 
em 3/10/73 8/10/73 15/10/73 31/10/73 7/11/73 14/11/73 28/11/73 18/12/73 
30 0.068 0.062 0.051 0.072 0.054 0.043 0.033 0.032 
21 60 0.100 0.093 0.083 0.102 0.089 0.083 0.082 0.081 
90 0.133 0.132 0.126 0.131 0.129 0.130 0.127 0.125 
120 0.140 0.141 0,137 0,139 0.137 0.138 0.136 0.136 
30 0.096 0.085 0.082 0.102 0.071 0.065 0.059 0.060 
22 60 0.105 0.100 0.096 0.103 0.093 0.093 0.093 0.092 
~ 0.126 0.123 0.121 0.116 0.113 0.115 0.116 0.116 
120 0.139 0.137 0.137 0.130 0.128 0.129 0.128 0.129 
30 0.077 0.069 0.062 0.073 0.052 0.049 0.048 0.049 
23 60 0.108 0.105 0.100 0.099 0.093 0.096 0.097 0.097 
90 0.135 0.123 0.127 0.124 0.'21 0.123 0.122 0.120 
120 0.144 0.136 0.135 0.133 0.130 0.134 0.132 0.132 
30 0.073 0.076 0.077 0.080 0.067 0.061 0.052 0.051 
24 60 0.119 0.118 0.119 0.119 0.115 0.115 0.111 0.110 
00 0.140 0.136 0.135 0.134 0.132 0.133 0.132 0.'31 
120 0.144 0.142 0.145 0.142 0.143 0.142 0.141 0.141 
~ 
APPENDIX 4c Soil moisture records for 1974 ~ 
.j;>. 
Plot No. Depth in Moisture Content (g) 
em 30/4/74 13/5/74 27/5/14 10/6/74 24/6/74 8/7/74 2217174 19/8/74 3/9174 
30 0.163 0.144 0.118 0.171 0.155 0.177 0.190 0.144 0.174 
60 0. •2 04 
1 0.171 0.160 
 0.196 0.189 0.196 0.205 0.176 0.197 
90 0.265 0.255 0.251 0.263 0.263 0.258 0.276 0.255 0.268 
120 0.273 0.254 0.250 0.261 0.266 0.267 0.276 0.252 0.265 
30 0.178 0.146 0.113 0.155 0.146 0.170 0.175 0.130 0.161 
2 60 0.144 0.142 0.127 0.146 0.147 0.148 0.147 0.127 0.166 
90 0.272 0.256 0.238 0.248 0.264 0.269 0.263 0.250 0.253 
120 0.295 0.285 0.275 0.282 0.289 0.289 0.315 0.273 0.282 
30 0.100 0.093 0.066 0.104 0.099 O.lJJ 0.132 0.087 0.129 
3 60 0.130 0.147 0.151 0.142 0.151 0.170 0.165 0.155 0.187 
ro 0.227 0.230 0.231 0.229 0.226 0.248 0.246 0.235 0.223 
120 0.321 0.295 0.291 0.~88 0.290 0.320 0.319 0.298 0.314 
30 0.122 0.081 0.051 0.097 0.079 0.094 0.109 0.069 0.100 
4 ro 0.174 0.168 0.158 0.197 0.183 0.185 0.195 0.164 0.193 
ElJ 0.241 0.233 0.212 0.221 0.227 0.230 0.240 0.216 0.236 
120 0.296 0.287 0.278 0.290 0.287 0.291 0.323 0.270 0.292 
30 0.162 0.139 0.088 0.160 0.154 0.162 0.169 0.127 0.152 
5 6() 0.184 0.185 0.162 0.182 0.195 0.191 0.201 0.167 0.196 
ro 0,278 0,272 0.236 0,261 0.285 0.269 0,338 0.249 0.267 
120 0.322 0.326 0.350 0.315 0.326 0.313 0.340 0.297 0,312 
Plot No. Depth in Moisture Content (9) 
em 30/4174 13/5174 27/Sn4 10/6174 24/6174 817/14 22/ 7/74 19/B/74 3/9/74 
30 0.216 0.189 0.159 0.208 0.191 0.216 0.223 0.171 0.217 
6 60 0.211 0.207 0.193 0.215 0.211 0.215 0.226 0.203 0.221 
9J 0.258 0.237 0.230 0.231 0.248 0.243 0.245 0.232 0.249 
120 0.321 0.316 0.306 0.307 0.319 0.317 0.321 0.283 0.325 
30 0.201 0.168 0.147 0.194 0.184 0.190 0.197 0.161 0.186 
7 60 0.210 0.089 0.184 0.197 0.207 0.21 1 0.218 0.188 0.205 
9J 0.284 0.276 0.276 0.279 0.283 0.285 0.286 0.269 0.281 
120 0.325 0.316 0.317 0.316 0.329 0,327 0.332 0,318 0.319 
30 0.206 0.182 0.156 0.204 0.198 0.209 0.217 0.189 0.208 
8 ro 0.277 0.243 0,252 0.254 0.268 0.268 0.269 0.254 0.258 
9J 0.284 0,275 0.278 0.272 0,275 0.277 0.286 0.268 0,279 
120 0.325 0.297 0.298 0.290 0.311 0,307 0.314 0.303 0.300 
30 0.182 0.158 0.127 0.179 0.175 0.189 0.196 0.153 0.182 
9 60 0.221 0.209 0.195 0.211 0.220 0.222 0.228 0.199 0.221 
9J 0.293 0.271 0.263 0.263 0.285 0.290 0.285 0.267 0.279 
120 0.329 0.320 0.313 0.313 0.332 0.315 0.335 0.311 0.327 
30 0.133 0.136 0.110 0.145 0.138 0.166 0.175 0.137 0.171 
60 
10 0.149 0.176 0.171 0.158 0.186 0.206 0.207 0.185 0.223 
9J 0.194 0.238 0.196 0.191 0.194 0.204 0.215 0.213 0.227 
120 0.251 0.221 0.227 0.226 0.232 0.244 0.232 0.244 0.253 
.. --~.-.---
~ 
\.J1 
-----~ 
Plot No. Depth in Moisture Content (9) ~ 
em 30/4/74 13/5/74 27/5/14 10/ 6/74 24/6/14 817114 22/1/74 19/ 8/74 3/9174 
30 0.096 0.073 0.048 0.072 0.069 0.08B 0.093 0.049 0.076 
11 00 0.211 0.197 0.187 0.186 0.207 0.213 0.212 0.190 0.202 
00 0.252 0.243 0.243 0.245 0.249 0.247 0.251 0.245 0.246 
120 0.259 0.233 0.235 0.238 0.246 0.254 0 .251 0.249 0 .247 
30 0.123 0.113 0.082 0. 126 0.102 0.126 0.126 0.090 0.121 
12 fXJ 0.207 0.207 0.207 0.212 0.210 0.213 0.212 0.160 0.215 
ro 0.213 0.219 0.222 0.225 0.223 0.220 0.222 0.227 0.224 
120 0.241 0.237 0.241 0.241 0.236 0.242 0.239 0.243 0.241 
30 0.088 0.074 0.039 0.087 0.079 0.090 0.102 0.064 0.090 
13 60 0.219 0.201 0.194 0.208 0.211 0.212 0.216 0.203 0.217 
9J 0.228 0.225 0.219 0.229 0.225 0.227 0.230 0.219 0.227 
12() 0.238 0.241 0.242 0.246 0.251 0.251 0.256 0.241 0.250 
30 0.090 0.063 0.036 0.071 0.064 0.085 0.081 0.061 0.072 
14 60 0.197 0.184 0.177 0.187 0.191 0.199 0.199 0.180 0.186 
9J 0.220 0.219 0.214 0.218 0.220 0.223 0.225 0.210 0.213 
120 0.226 0.218 0.215 0.217 0.217 0.221 0.223 0.212 0.214 
30 0.072 0.052 0.022 0.061 0.053 0.068 0.075 0.041 0.072 
15 fI) 0.153 0.130 0.118 0.135 0.139 0.145 0.150 0.126 0.141 
ro 0.216 0.208 0.205 0.208 0.215 0 .210 0.211 0.20B 0.215 
120 0.237 0.231 0.227 0.232 0.235 0.232 0.234 0.231 0.231 
Plot No. Depth in Moisture Content (g) 
em 30/4114 13/5/74 21/5174 1016/14 24/6174 817174 2217174 1918/74 319174 
30 0.079 0.103 0.028 0.075 0.058 0.081 0.088 0.040 0.077 
16 60 0.119 0.099 0.086 0.102 0.103 0.114 0.123 0.092 0.111 
00 0.147 0.161 0.149 0.153 0.163 0.164 0.171 0.153 0.158 
120 0.251 0.244 0.233 0.237 0.244 0.244 0.249 0.236 0.238 
30 0.120 0.109 0.075 0.120 0.109 0.124 0.137 0.087 0.129 
17 60 0.181 0.176 0.171 0.184 0.179 0.184 0.185 0.171 0.186 
~ 0.208 0.204 0.209 0.207 0.204 0.213 0.209 0.202 0.211 
120 0.225 0.228 0.226 0.224 0.227 0.234 0.231 0.221 0.234 
30 0.055 0.045 0.024 0.042 0.038 0.050 0.050 0.033 0.047 
18 60 0.064 0.055 0.049 0.056 0.058 0.062 0.065 0.055 0.061 
00 0.105 0.098 0.095 0.096 0.100 0.102 0.102 0.100 0.101 
120 0.125 0.121 0.119 0.119 0.124 0.123 0.121 0.123 0.123 
30 0.073 0.069 0.052 0.076 0.072 0.077 0.079 0.064 0.078 
19 60 0.099 0.090 0.090 0.096 0.096 0.098 0.101 0.092 0.095 
ro 0.126 0.122 0.121 0.123 0.126 0.128 0.125 0.121 0.123 
720 0.134 0.134 0.135 0.136 0.136 0.137 0.136 0.134 0.135 
30 0,050 0.041 0.024 0.041 0.033 0.052 0.057 0,041 0.056 
20 60 0.076 0.065 0.063 0.069 0.068 0.072 0.075 0.065 0.071 
90 0.130 0.128 0.128 0.127 0.130 0.129 0.131 0.127 0.107 
720 0.138 0.137 0.137 0.134 0.137 0.136 0.136 0.131 0.137 
~ 
~ 
Plot No. Depth in Moisture Content (9) 
em 30/4/74 13/5174 27/5174 10/6/74 24/6174 817174 2217174 19/8/74 319174 
30 0.057 0.047 0.029 0.051 0.047 0.055 0.055 0.034 0.052 
21 60 0.097 0.094 0.091 0.096 0.097 0.098 0.100 0.087 0.098 
[J) 0.131 0.128 0.125 0.127 0.130 0.130 0.129 0.124 0.126 
120 0.137 0.135 0.137 0.134 0.135 0.137 0.137 0.131 0.135 
30 0.097 0.090 0.076 0.094 0.093 0.094 0.100 0.078 0.094 
22 00 0.112 0.111 0.108 0.115 0.115 0.113 0.117 0.105 0.113 
[J) 0.123 0.117 0.117 0.122 0.122 0.122 0.126 0.117 0.125 
120 0.135 0.130 0.132 0.134 0.136 0.134 0.137 0.129 0.134 
30 0.074 0.060 0.046 0.061 0.056 0.067 0.073 0.053 0.071 
23 60 0.112 0.107 0.104 0.110 0.111 0.111 0.110 0.105 0.111 
3) 0.130 0.129 0.128 0.13) 0.130 0.130 0.130 0.126 0.131 
120 0.138 0.138 0.139 0.138 0.138 0.138 0.138 0.137 0.141 
30 0.064 0.051 0.040 0.052 0.049 0.060 0.063 0.042 0.059 
24 60 0.106 0.101 0.099 0.104 0.102 0.107 0.109 0.096 0.104 
[J) 0.117 0.125 0.124 0.126 0.123 0.127 0.130 0.122 0.126 
120 0.123 0.130 0.130 0.133 0.131 0.137 0.137 0.130 0.134 
P nnted at 111 A, /oodan NIgeria