Effect of nitrogen fertilizer and harvesting stage on yield and quality of natural pasture in Fogera District, North Western Ethiopia

Abate, A. Haramaya University, Haramaya (Ethiopia). 2008. Effect of nitrogen fertilizer and harvesting stage on yield and quality of natural pasture in Fogera District, North Western Ethiopia. MSc thesis (Range Ecology and Management). 78p. Haramaya (Ethiopia): Haramaya University.

This experiment was carried out to assess botanical composition, DMY and chemical composition of Fogera upland natural pastureland under different application rates of N fertilizer and harvesting stages of natural pasture at smallholder farmers condition. The experiment was conducted using 3 x 4 factorial experiment arranged in a randomized complete block design with three replications and the treatment consisted three stages of harvesting (60, 90 and 120 days) and four levels of N fertilizer application (0, 23, 46 and 69 kg N/ha) on the natural pasture land. The botanical composition of the natural pasture land that have been identified at the experimental site included thirteen grasses, seven annual legumes and seven other herbaceous species belonging to different families. The influence of stages of harvesting was significant (P<0.05) but application of N fertilizer was not significant on total DMY of the pasture. Natural pasture harvested at 120-days of harvesting and at a fertilizer application of 69 kg/ha results the highest DMY (9.97 t/ha) while the lowest level was (5.38 t/ha) from unfertilized plots at 120-days of harvesting. The effect of stage of harvesting and fertilizer level on DMY of legume components was highly significant (P<0.001) but for the grass components stage of harvesting had non- significant effect, where as fertilizer had a highly significant effect (P<0.001). The relative proportion of legumes in the pastureland reached highest at 90-days of harvesting at all levels of fertilizer application. The proportion of legumes varied from the highest mean of 56.18% to the lowest of 37.66% at 90 and 120-days of harvesting, respectively while that of grasses ranged from 58.09% to 40.24% at 120 and 90-days of harvesting, respectively. The relative proportion of grasses increased with increasing levels of N fertilizer and stage of harvesting up to 120-days. Significant effect of stage of harvesting (P<0.001) on CP, NDF, ADF, hemi-cellulose, cellulose, P and IVDMD were obtained at all levels of fertilizer application. At 60-days of harvesting, highest values of 15.53%, 0.41% and 54.86% were obtained for CP, P and IVDMD, respectively. However, the lowest values 55.63%, 37.32%, 17.55% and 32.02% were obtained for NDF, ADF, hemi-cellulose and cellulose, respectively at the same stage of harvesting. The CP content was significantly (P<0.001) lower (6.76%) at 120-days of harvesting compared with other stages of harvesting. At all levels of N- fertilizer, the mean CP content obtained were above the reported critical level for ruminant’s microorganism’s functioning (7%). The IVDMD at 90 and 120-day harvesting was 50.09% and 38.76%, respectively. The values at all harvesting stages were below the reported threshold value that ranged between 55 and 70% for medium quality forages from natural pastures. The results obtained in the present study revealed that fertilizer application increased the yield of natural pasturelands by 36.07%. Fertilizer applications at the level of 46 kg/ha resulted in higher mean dry matter yield of 9.58 t/ha and higher nutritional quality (11.89% CP, 1.08 t/ha CPY, 49.91% IVDMD and 4.65 t/ha IVDMDY) of the natural pasture. This level of fertilizer application combined with 90 days of (October) harvesting should be practiced for higher Pasture yield and quality parameters.