The Effect of Bradyrhizobium Strains on Monocropped and Intercropped Soybean (Glycine max L. Merr.) Biomass and Protein

Abstract

AbstractIntercropping soybeans with corn can produce yields of silage comparable to monocrops of corn but with a higher protein concentration. To maximize N2‐fixation by soybeans, it is important to use a strain of bradyrhizobium that is well adapted to local soil and climate conditions. In 1991 and 1992 an experiment was conducted in Truro, Nova Scotia, Canada, to compare a locally isolated bradyrhizobium strain. NS1 with a commercial strain (COM). Corn‐soybean intercrops and soybean monocrops were grown and various response variables were measured to assess the efficacy of each strain. NS1 proved to be superior to the commercial strain of bradyrhizobium in both intercrops and monocrops when soybean plant protein concentration, soybean seed protein concentration and soybean seed biomass yield were measured. For intercrop protein yield and intercrop protein concentration NS1 outperformed COM only in monocrops. Protein yields per hectare of soybeans grown in either system were higher when NS1 was used as an inoculant. No differences were observed between inoculants in biomass yields of soybeans grown in either system. Since soybeans only contributed 28.5% to the total biomass of intercrops, the biomass of the corn probably masked the differences between the two inoculants for intercrop protein yield and concentration. However, even under the stressful conditions for soybean plants associated with intercropping, soybean protein concentrations and yields when grown in intercrops were higher for the NS1 strain of bradyrhizobium. It appears that selection of a locally adapted strain of inoculant for soybeans can prove useful in both monocropping and intercropping systems.