Symbiotic and Agronomic Performance of Cowpea Rhizobial Inoculants from Soil of Ethiopia under Field Conditions

The effect of inoculating indigenous cowpea nodule bacteria of Ethiopia on the crop performance was not tested under field condition with the ultimate goal of selecting effective inoculants. Root nodule bacteria which showed strong symbiotic effectiveness under greenhouse condition were selected for field experiment. Under field conditions, inoculation of cowpea with ECR-0+ECE-21 and ECR-101+ECE-21 resulted in a maximum grain yield (GY, 2713 kg ha-1) and above ground biomass (BW, 506 g m-2), respectively. The co-inoculation of cowpea with ECR-0 and ECE-21 and ECR-24 and ECE-21 significantly improved (p<0.05) the N-content and GY as compared to their single rhizobial inoculation. The native strains performed better than the exotic strain (Biofix). Performance of the strains was similar at the two test locations except ECR-14 and ECR-24 that resulted 13% greater of BW at Uke than at Bako. Symbio-agronomic performance of native rhizobia under field condition showed direct correlation (r>0.5; p<0.01) to each other except nodule number. In general, both single and co-inoculation of the native rhizobacterial inoculants improved cowpea performance. This is a promising biofertilizer to enhance cowpea production in Ethiopia, where the farmers cannot afford to buy chemical fertilizers.