THE Interaction between soybean (glycine max [l]. merril) genotype, soil type and inoculant strain with regard to production potential, seed protein and nitrogen content.

Abstract

A growth chamber study was conducted using three soybean (Glycine max [L.] Merrill) genotypes (Barc-9, Avuturda and Talana), three Bradyrhizobium japonicum inoculant strains (WB 108, WB 112 and WB 1), and three soil types ( Avalon, Arcadia and sand). The aim of the study was to evaluate the amount of N2 fixed by the different genotype x soil type x inoculant strain combinations, using different parameters. The performance of the South African strain (WB 1) was also compared to the Brazilian and USA strains (WB 112 and WB 108 respectively) and an uninoculated control. Most significant interactions were found to be soil type x inoculant strain and soil type x genotype interactions, which indicated that genotypes and inoculant strains differ in their ability to perform in different soil types. This finding confirms that soybean production in South Africa can be improved by selection of genotypes and inoculant strains for their compatibility in different soils. Genotypic differences were observed for seed and seed protein yield. Leaf-N, ureide-N and nodule fresh mass did not reflect the protein content of the seeds. A high soil N content and a low soil pH inhibited N2 fixation and yield. Nodule fresh mass, foliar N content and shoot to root ratio correlated negatively with the clay content of the soil. Plants inoculated with WBl 12 had the highest (significant, p<0.01) nodule fresh mass of all the inoculation treatments, but not the highest N2 fixation and yield. Plants inoculated with WB108 had the highest (significant, p<0.01) leaf-N. Inoculation with WBl resulted in the highest (significant, p<0.01) seed protein yield