Seed certification and maize, 
rice and cowpea productivity 
in Nigeria: 
An insight based on nationally 
representative farm household 
data and seed company location 
data
(WP5 Nigeria Study 2022)
Hiroyuki Takeshima (presenter) 
Senior Research Fellow, IFPRI
Seed Equal: Reflect, Assess, and Plan 
Addis Ababa, 13-17 March 2023
Background and objectives
Background
 Significant interests in seed certification expansion in Nigeria
 Limited evidence on seed certification impacts
Objectives
 Assess heterogeneous returns to seed certification 
 Generate evidence toward more flexible, decentralized seed 
quality assurance systems in Nigeria
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Seed quality assurance in Nigeria
 National Agricultural Seeds Seed inspectors per million ha of 
Council Act 2019 empowered arable land
NASCs to provide legal backing Zambia 31.1
for seed certification Madagascar 20.0
Ghana 17.1
 Certified seed production Zimbabwe 15.0
South Africa 15.0
 Private companies – 95% Malawi 10.3
Mali 9.4
 Procured by local gov’t for Kenya 8.6
distribution (rest sold Burkina Faso 7.5
directly by dealers) Rwanda 6.9
Senegal 6.6
 Varietal diversity - limited Burundi 5.8
Mozambique 4.4
 Seed Certification Officers are Tanzania 3.6
located in Agricultural Liberia 2.0
Development Project (ADP) area Ethiopia 2.0
in each state Nigeria 1.7
Uganda 1.0
 QDS - limited Source: Number of seed inspectors from Mabaya et al. (2021), Waithaka et 
al. (2019, 2021). Arable land are from FAOSTAT (2022).
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Certified seed production in Nigeria has 
varied at significant scale over time
200,000 120
100
150,000
80
100,000 60
40
50,000
20
0 0
Maize (Hybrid) Maize (OPV) Maize Rice
Rice (Lowland) Rice (Upland)
Others
Source: Calculations based on NASC annual reports  in left-hand side panels, and FAOSTAT in right-hand side panels.
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tons
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2020
Inedx (Proportion to seed 
used: Seed use = 100)
2010
2011
2012
2013
2014
2015
2016
2017
2020
Certified seed production for cowpea 
gradually increasing
1,400 1.0
1,200 0.9
0.8
1,000 0.7
800 0.6
0.5
600 0.4
400 0.3
0.2
200 0.1
0 0.0
Cowpea Cowpea
Source: Calculations based on NASC annual reports  in left-hand side panels, and FAOSTAT in right-hand side panels.
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tons
2009
2010
2011
2012
2013
2014
2015
2016
2017
2020
Index (Proportion to seed used: 
Seed use = 100)
2010
2011
2012
2013
2014
2015
2016
2017
2020
Certified seeds production by seed 
company headquarter locations 
2009 2009 2009
2011 2011 2011
2014 2014 2014
2017 2017 2017
2020 2020 2020
Maize Rice Cowpea
Source: Compilations from NASC annual reports (various years) (Takeshima et al. 2022).
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Empirical methods
Panel fixed effects regression
𝒚𝒚𝒌𝒌𝒌𝒌𝒌𝒌𝒌𝒌 = 𝛼𝛼 + 𝛽𝛽1𝑺𝑺𝒌𝒌𝒌𝒌𝒌𝒌 + 𝛽𝛽2𝑺𝑺𝟐𝟐𝒌𝒌𝒌𝒌𝒌𝒌 + 𝛾𝛾𝑋𝑋𝑖𝑖𝑖𝑖𝑖𝑖 + 𝑢𝑢𝑘𝑘𝑖𝑖𝑖𝑖 + 𝜀𝜀𝑘𝑘𝑖𝑖𝑖𝑖𝑖𝑖
Yield Certified seeds Farmer 
(k = crop, produced by seed fixed 
i = farmer companies effects
j = LGA/State headquartered in 
 t = Year) LGA/State j
𝒚𝒚𝒌𝒌𝒌𝒌𝒌𝒌𝒌𝒌 = 𝛼𝛼 + 𝛽𝛽𝐶𝐶 ⋅ 𝑪𝑪𝒌𝒌𝒌𝒌𝒌𝒌𝒌𝒌 + 𝛽𝛽𝐶𝐶𝐶𝐶𝐶 ⋅ 𝑪𝑪𝒌𝒌𝒌𝒌𝒌𝒌𝒌𝒌 ⋅ 𝑍𝑍𝑖𝑖𝑖𝑖 + 𝛽𝛽𝐶𝐶 ⋅ 𝑋𝑋𝑖𝑖𝑖𝑖𝑖𝑖 + 𝜐𝜐𝑘𝑘𝑖𝑖𝑖𝑖 + 𝜀𝜀𝑘𝑘𝑖𝑖𝑖𝑖𝑖𝑖
Certified seeds Agroclimatic 
used (yes = 1) conditions
Instrumental 𝑺𝑺
variables 𝑺𝑺𝒌𝒌𝒌𝒌𝒌𝒌 𝒌𝒌𝒌𝒌𝒌𝒌 ⋅ 𝑍𝑍𝑖𝑖𝑖𝑖
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Data
 LSMS-ISA (NBS & World Bank) 
 Certified seeds produced by seed companies (NASC annual 
reports)
 Seed company headquarter locations (NASC)
 Agroclimatic data (Various sources)
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Positive but declining marginal returns: 
Maize
Categories Use improved Use of certified seeds Use of certified seeds Yield (proportional 
varieties (yes = 1) (yes = 1) (improved) (yes = 1) increase)
Certified seed production -0.178 0.465*** -0.020 0.309***
(States of seed companies) (0.149) (0.170) (0.295) (0.103)
Square term 0.175 -0.236* 0.134 -0.149
(0.117) (0.127) (0.199) (0.091)
Certified seed production      1.040*** 0.712*** 0.547*** 0.109
(LGA of seed companies) (0.137) (0.144) (0.183) (0.068)
Square term –0.804*** –0.594*** –0.415*** –0.121***
(0.116) (0.112) (0.141) (0.037)
Other controls Yes Yes Yes Yes Yes Yes Yes Yes
Wave dummy Yes Yes Yes Yes Yes Yes Yes Yes
Intercept Yes Yes Yes Yes Yes Yes Yes Yes
Samples responding at least two 650 650 650 650 650 650 1945 1945
rounds
Source: Takeshima et al. (2022). ***1% **5% *10%
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Rice - similar patterns
Categories Use improved Use of certified seeds Use of certified seeds Yield (proportional 
varieties (yes = 1) (yes = 1) (improved) (yes = 1) increase)
Certified seed production -6.455 -0.442 2.123*** -0.217
(States of seed companies) (7.050) (5.054) (0.985) (0.529)
Square term -6.713 3.401 –1.251*** 0.261
(6.291) (1.859) (0.361) (0.362)
Certified seed production      0.565 -0.149 1.722** 0.145**
(LGA of seed companies) (1.148) (0.752) (0.657) (0.066)
Square term -0.489 -0.136 –1.147** –0.124**
(0.936) (0.686) (0.529) (0.059)
Other controls Yes Yes Yes Yes Yes Yes Yes Yes
Wave dummy Yes Yes Yes Yes Yes Yes Yes Yes
Intercept Yes Yes Yes Yes Yes Yes Yes Yes
Samples responding at least two 102 102 102 102 102 102 509 509
rounds
Source: Takeshima et al. (2022). ***1% **5% *10%
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Cowpea - similar patterns
Categories Use improved Use of certified seeds Use of certified seeds Yield (proportional 
varieties (yes = 1) (yes = 1) (improved) (yes = 1) increase)
Certified seed production 0.890** 0.612 0.646 0.464***
(States of seed companies) (0.385) (0.432) (0.426) (0.128)
Square term –0.523** –0.288 –0.508** –0.438***
(0.204) (0.219) (0.201) (0.107)
Certified seed production      0.098 0.488*** 0.029 0.013
(LGA of seed companies) (1.116) (0.120) (0.124) (0.019)
Square term -0.119 –0.511*** 0.015 0.000
(0.114) (0.120) (0.124) (0.015)
Other controls Yes Yes Yes Yes Yes Yes Yes Yes
Wave dummy Yes Yes Yes Yes Yes Yes Yes Yes
Intercept Yes Yes Yes Yes Yes Yes Yes Yes
Samples responding at least two 436 436 436 436 436 436 2076 2076
rounds
Source: Takeshima et al. (2022). ***1% **5% *10%
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Declining marginal returns to seed 
certification
𝜌𝜌𝑙𝑙 𝜌𝜌∗ 𝜌𝜌ℎ
Policy and regulatory costs
Source: Spielman (2022).
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Seed sector value/growth 
($, %)
Heterogeneous returns to certified seeds 
due to agroclimatic conditions 
Determinants of yield OLS-fixed effects OLS-fixed effects IV-fixed effects 
model model model
Coef. Coef. Coef. 
(s.e.) (s.e.) (s.e.)
Used certified seed × Soil 0.424* (0.207) 0.289 (0.228) 0.900 (0.572)
alkalinity
× Organic contents -0.342** (0.149) -0.361** (0.172) -1.476***(0.507) Soil alkalinity Soil organic Soil drainage 
× Soil texture (medium) 0.096 (0.173) 0.013 (0.176) 0.268 (0.417) (pH) contents property
× Soil texture (fine) 0.119 (0.123) 0.147 (0.134) 0.147 (0.323)
× Soil salinity 0.007 (0.114) 0.100 (0.110) -0.155 (0.293)
× Soil sodicity -0.046 (0.175) -0.055 (0.182) -0.050 (0.415)
×Soil drainage (poor drainage) 0.258* (0.133) 0.269** (0.127) 0.071 (0.288)
× Soil drainage (excess drainage) 0.185 (0.159) -0.032 (0.180) 0.020 (0.421)
× Rainfall z-score 0.510 (0.322) 0.638* (0.351) -1.526* (0.931)
× Temperature z-score 0.076 (0.129) 0.275** (0.126) -0.735** (0.309)
× Wind -0.018 (0.202) 0.299 (0.209) -1.898***(0.609)
× ln (farm size) 0.255** (0.117) 0.264** (0.121) -0.263 (0.381)
× ln (agricultural capital) 0.261** (0.119) 0.176 (0.118) 0.463 (0.338)
× ln (asset) -0.074 (0.102) -0.231** (0.112) -0.365 (0.287)
× Female household head -0.129 (0.111) -0.169 (0.123) -0.617** (0.270)
Used certified seed Yes Yes Yes
Used certified seed × maize Yes Yes Yes Wind Rainfall Temperature 
Used certified seed × rice Yes Yes Yes anomaly anomaly
Geopolitical zone dummy Yes Yes Yes
Other control variables Yes Yes Yes
Certified seed production by Yes
seed companies in the state
Number of observations (panel 920 920 920
samples growing the same 
crops in both waves)
p-value (H0: model insignificant) .000 .000 .000
p-value (H0: not overidentified) .380
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Source: Takeshima et al. (2022). ***1% **5% *10% 12
Policy recommendations 
 Revisit seed certification target in Nigeria
 Excessive expansion of certified seed production may not necessarily lead to 
higher use rates or yield outcomes when compared to more moderate levels of 
certified seed production
 Prioritize spatially the seed certification expansion effort if it is still of policy importance:
 continue research to better identify locations with higher returns to certified seeds, 
given agroecological / socio economic conditions and currently popular varieties
 prioritize in those locations
 certification capacity enhancement / deployment of inspectors => this may encourage seed companies 
to invest in certified seed production in those areas
 enforcement capacity (i.e., spot check of certified seeds sold by dealers conducted by NASC)
 Identify and prioritize where hybrid maize is more widely adopted (so that 
certification efforts shift relatively more to hybrid maize)
 Promote more decentralized systems, like QDS / community seed schemes for rice, 
cowpeas, OPV maize (as in various Eastern and Southern African countries)
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More details available in IFPRI Discussion Paper:
Takeshima H, T Abdoulaye, KS Andam, HO Edeh. A Fasoranti, B 
Haile, P. Lava Kumar, C Nwagboso, C Ragasa, D Spielman, T 
Wossen. (2022). Seed certification and maize, rice and cowpea 
productivity in Nigeria: An insight based on nationally 
representative farm household data and seed company 
location data. IFPRI DP 02147. 
https://doi.org/10.2499/p15738coll2.136474
Thank you !