Effects of soybean [Glycine max (L.) Merrill] inoculation in a soil with established population of Bradyrhizobium with strains SEMIA 566, 586, 587, 5019, 5079 and 5080

Abstract

The effects of soybean [Glycine max (L.) Merrill] inoculation were studied in three experiments carried out in an oxysol with established population of Bradyrhizobium (2.21x10⁵ cells/g of soil). The six strains evaluated, two classified as B. japonicum and four as B. elkanii, were capable to establish in the rhizosphere and increase the percentage of nodule occupancy in roots. Increases in soybean yield of up to 420 kg/ha, and of 13.5% in the total N content of grains due to inoculation, were observed in relation to the non-inoculated treatment receiving N fertilizer. When wheat (Triticum aestivum L.) was grown in the same plots, during the winter, without receiving N fertilizers or inoculants, a positive and statistically significant correlation was observed between the treatments that have shown higher rates of N₂ fixation and the N content in wheat grains. Inoculation of the same plots, with the same treatments, in the following season (93/94) resulted, again, in an enhancement of yield and total N content in soybean grains.