Symbiotic effectiveness of inoculation with Bradyrhizobium isolates on Cowpea (Vigna unguiculata (L.) Walp) varieties

Cowpea (Vigna unguiculata (L.) Walp) is one of the widely cultivated crops, contributing for sustainable farming development due to its excellent nitrogen contribution via symbiosis. The response of Bradyrhizobium inoculants depends on the compatibility of the strain and the legume crop. Therefore, the current work aimed to evaluate the symbiotic effectiveness of the Bradyrhizobium isolates with cowpea varieties tested on sand. For these purpose, five Bradyrhizobium isolates (CP-24, CP-10, CP-37, GN-33 and GN-102) and five cowpea varieties (Keti (IT99K-1122), TVU, Black eye bean, White wonderer trailing and Bole) were used. The experiment was arranged using CRD, with three replicates. The result of the experiment showed, significant (P = 0.05) differences for all the measured parameters. White wonderer trailing inoculated with CP-24 exhibited the higher plant height (28.33 cm), whereas, the least plant height recorded when Keti (IT99K-1122) variety was inoculated with GN-102. The highest nodule number per plant (47.67) recorded from CP-24 inoculated Black eye bean variety. The highest nodule dry weight recorded from CP-24 inoculated TVU variety. A pink nodule color and green leaf observed from the cowpea varieties inoculated with Bradyrhizobium isolates. For all the parameters considered, the control treatments showed significantly lower performance compared with the inoculated treatments. Hence, this study proves the need for Bradyrhizobium inoculation to improve the growth, biomass and nodulation performance, and to use these isolates for field production of cowpea in the study area and similar agro-ecologies.