Economic value of dual-purpose cowpea as affected by variety, fertilizer, and environment

Across the semiarid regions of West Africa, cowpea (Vigna unguiculata (L.) Walp) varieties grown by farmers are either grain- or forage-only, and often fields are not fertilized. Information regarding profitability of dual-purpose over traditional varieties and fertilizer application in cowpea production system is limited. The main objective of this study was to quantify the economic value of newly released dual-purpose and forage cowpea varieties and fertilizer inputs across the Senegalese peanut basin. This field study was conducted across three locations in Senegal (Bambey, Boulel, and Darou Mousty) in 2021 and 2022. Treatments were 20 cowpea varieties in the main plot and two levels of fertilizer (an unfertilized control and fertilized) in the subplot. Cowpea varieties E-BC4STR1, E-BC4STR5, E-BC4STR11, Kelle, and Melakh had relatively greater grain yields (average 429-474 kg ha-1) in all environments. Forage varieties 66-35F and 58-74F produced the most forage (average 2353 and 1717 kg ha-1) yields across environments. Fertilizer-NPK application increased grain yield by 22%-40% in most environments. Unlike grain yield, varietal effects on forage yields occurred only with fertilizer application. Dual-purpose cowpea varieties E-BC4STR1, E-BC4STR2, E-BC4STR5, and E-BC4STR11 had a stable, significant economic value in our study compared with grain-only variety Yacine (traditional variety) or forage variety 66-35F. Fertilizer-NPK increased net revenue in four out of six environments. We conclude that using dual-purpose cowpea varieties provided significant economic advantage over traditional varieties, and application of fertilizer further increased the economic value. However, further studies are needed to determine the economically optimal fertilizer rate.