Improvement of yield parameters of cowpea (<i>Vigna unguiculata</i>) by rhizobia sp. isolated from <i>Mucuna pruriens</i> and <i>Centrosema pubescens</i> at Ile-Ife, Nigeria

Abstract This research was conducted to isolate, authenticate, and assess the symbiotic effectiveness of cowpea nodulating rhizobia isolated from Centrosema pubescens and Mucuna pruriens at different locations in Ile-Ife, Nigeria with two varieties of cowpea (Ife BPC and Ife Brown). Thirteen Rhizobium and three Bradyrhizobium species were isolated and all of them significantly enhanced nodulation with Ife brown and Ife BPC cowpeas having 50% and 81.25% effective nodules formation, respectively. The inoculation of the cowpea with Bradyrhizobium sp (C7) increased the yields significantly with Ife brown recording 73.92 g, while Ife BPC had 58.14 g. The symbiotic relationship between the rhizobia species and the two varieties of cowpea increased the soil fertility with nitrogen concentration in the soil increasing to 84.28 mg/g for Ife brown and 55.89 mg/g for Ife BPC. All the sixteen rhizobia isolates were resistant to Carbendazim 12% + Mancozeb 63% W/P; 2,3 Dichlorovinyl dimethyl phosphate; Chlorpyriphos; Atrazine and 2,3 Dimethylamine. In contrast, four Rhizobium sp. were sensitive to Glyphosate at 14.4 mg/ml, while paraquat had inhibitory effect on 14 out of the 16 rhizobial species at 2.76 mg/ml. This study concluded that the rhizobia isolates improved the cowpea yield and also enriched the soil compared to the Nitrogen, Phoshorus and potassium (NPK) fertilized soil.