INFLUENCE OF BRADYRHIZOBIUM AND TWO GLOMUS SPECIES ON THE GROWTH AND YIELD OF SOYBEAN

A screenhouse experiment was conducted to investigate the effect of Bradyrhizobium japonicum on the response of soybean to inoculation with two species of mycorrhiza (Glomus mosseae and Glomus deserticola). The study was carried out in a screenhouse with soybean as test crop. The two species of arbuscular mycorrhiza fungi (AMF) were inoculated to the potted soil with or without B. japonicum. Single super phosphate (SSP) and zero amendment served as conventional and absolute control respectively. The experimental design was randomized complete block with 4 replicates. AMF/Bradyrhizobium interaction increased mycorrhizal fungi root colonization significantly (p = 0.05) by at least 35.9% at early growth stage (3 weeks after planting (WAP)) and 59.5% at later growth stage (9 WAP). G mosseae/Bradyrhizobium interaction significantly increased N and P uptakes by 68.9 and 80.0%, respectively, as well as plant height, number of leaves, number of branches, canopy spread and leaf area between 2 and 5 WAP. Soybean biomass increased significantly due to interaction of G mosseae and Bradyrhizobium by 42.2-53.4% between 3 and 9 WAP and nodule weight increased by 61.9-93.3% between 6 and 9 WAP. Grain yield per plant was similar in all AMF treatments and SSP but less in sole Bradyrhizobium inoculation by 37.5% and in control by 33.3%. AMF/Bradyrhizobium interactions produced higher N by up to 81% in the residual soil and the P content was similar to SSP but higher than in control by up to 32.3%. Interaction of G mosseae and Bradyrhizobium increased spores of mycorrhizal fungi in the soil by 41% at 3 WAP and 74.7% at 9 WAP. It was concluded that although Bradyrhizobium had a positive and synergistic influence on the activities of the two species of mycorrhizal fungi inoculated on soybean, the influence was, however, more pronounced on G mosseae than G deserticola