Adoption and ex-post impacts of improved cowpea varieties on productivity and crop incomes in Nigeria
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Despite successes of international and national crop improvement research in the development and release of a number of improved grain legume varieties, there is limited empirical evidence of adoption and ex-post impacts of improved legumes. Cowpea covers the largest area of any grain legume in Africa and is especially important in West Africa, with Nigeria and Niger alone accounting for over 75% of the total cowpea production. Using a nationally representative survey data from a sample of 1525 cowpea growing households cultivating over 1000 plots, this paper assesses the adoption and impacts of improved cowpea varieties on cowpea yields and net crop income in northern Nigeria. The study applies the control function approach as well as endogenous switching regression and marginal treatment effects models to estimate the causal effects of adoption of improved cowpea varieties. The results show that 38% of the sample households adopted improved varieties, and cowpea yields and crop incomes increase significantly with the adoption of improved cowpea varieties. . Adoption of improved cowpea varieties is associated with 29–40% yield gains and 26–28% income gains. The paper concludes with implications for policy and research aimed at promoting adoption and impacts of improved cowpea varieties in Nigeria.