Yield response of field‐grown cowpea varieties to Bradyrhizobium inoculation

Abstract Cowpea [Vigna unguiculata (L.) Walp.] is a widely cultivated crop for food and animal feed, with a high potential for alleviation of climate change effects on crop production due to its biological nitrogen fixing ability. However, its yields are low in Ethiopia partly due to poor agronomic practices such as lack of improved varieties, low soil fertility, and limited input use including bio‐inoculants. Field experiments were conducted in the cropping seasons 2018 and 2019 at three climate change and food insecurity vulnerable sites in Ethiopia (Boricha, Dore, and Hawassa) to determine yield responses of cowpea varieties to Bradyrhizobium inoculation. Four cowpea varieties, Keti (IT99K‐1122), TVU, Black eye bean, and White wonderer trailing in combination with three inoculation levels (un‐inoculated or inoculated with Bradyrhizobium strains CP‐24 or CP‐37) were used in a factorial randomized complete block design with four replications. Results revealed significant varietal differences in crop yield and yield components over years and across sites. Averaged over the seasons, seed yield of TVU was higher by 52% compared to the low‐yielding Black eye bean variety. On average of the three sites, inoculation of cowpea with strain CP‐24 significantly increased seed yield (21%), pod number (16%), and 100‐seed weight (13%) relative to the control. Furthermore, the interaction between variety and inoculant resulted in a significant increase in seed yield and number of pods per plant of TVU × CP‐24 by 60 and 68%, respectively, as compared to the un‐inoculated treatment. Overall, inoculation of the cowpea varieties TVU and White wonderer trailing with Bradyrhizobium strains CP‐24 is recommended at all the three tested sites and similar agro‐ecological environments for improved productivity of cowpea.