Effects of Rhizobial Inoculant and Nitrogen Fertilizer on Yield and Nodulation of Common Bean Under Intercropped Conditions

The effects of mixed granular rhizobial strains and application of modest amount of nitrogen fertilizer (starter nitrogen fertilizer) on yield and nodulation of five common bean (Phaseolus vulgaris L.) varieties under bean–sorghum intercropped conditions was investigated for two crop seasons. The soil upon which the study was conducted has been noted for its low organic matter content and low nitrogen status. Results showed that inoculation with mixed granular rhizobial inoculant and use of starter nitrogen fertilizer significantly improved both yield and nodulation of common bean varieties in most of the cases. Some varieties were noted to be non-responsive to inoculation with mixed granular rhizobia and application of nitrogen fertilizer. Yield and nodulation were found to have significant positive correlation for both crop reasons. For the bean–sorghum intercropped conditions, the use of mixed granular rhizobial inoculant and starter nitrogen fertilizer is indispensable to realize the benefits of biological nitrogen fixation on highly degraded Regosols of the Hararghe Highlands.