Effect of soil proximity to homestead, nitrogen source on nodulation and nodule activity of some cowpea (Vigna unguiculata (L.) Walp) varieties

Abstract

Integration of Bradyrhizobial inoculation with improved cowpea varieties is one viable option to enhance cowpea nodulation and nitrogen fixation, resulting in sustainable cowpea production. This study was conducted in a screen house to determine the effects of soil proximity to the homestead, nitrogen source on nodulation, and nodule activity of some cowpea varieties. This study involved the factorial combination of soil proximity to homestead: close and far; nitrogen source: control (no nitrogen application), application of urea (100 kg N ha-1), inoculation with Bradyrhizobium strain BR 3262, Bradyrhizobium strain BR 3267, and cowpea varieties: Kanannado, IT93K-452-1, IT97K-499-35, and IT90K-277-2, arranged in a completely randomized design and replicated three times. Results revealed that the Most Probable Number (MPN) count of the cultivated soils to cowpea varieties ranged from (9.26 - 12.27 x 106). Results show that the field's proximity to the homestead did not significantly (P > 0.05) differ from that away from the homestead. Inoculation with BR 3262 significantly (P < 0.05) improved nodule number and dry weight by 62% and 66%. Kanannado significantly increased nodulation compared to the improved varieties. Inoculation with BR 3267 had more nodules than un-inoculated control and N treatment. The result indicates that using Bradyrhizobium strain BR 3262 or BR 3267 and Kanannado variety could improve cowpea nodulation. Further study should, however, be carried out under field conditions to affirm this study.