Merrill] Effects of endophytic Streptomyces sp.; P4 isolate and Bradyrhizobium japonicum USDA 110 on nodulation, nitrogen fixation and yield of soybean [Glycine max (L.) Merrill]

Abstract

The agrochemicals which harm farmers, consumers’ health and the environment are still being used with rhizobia in soybean production. The objective of this study was, therefore, to study the effects of endophytic Streptomyces sp.; P4 isolate and Bradyrhizobium japonicum USDA 110 on nodulation, nitrogen fixation and yield of soybeans [Glycine max (L.) Merrill]. The Chiang Mai 2 soybean variety was used in a pot experiment. The experimental design was a completely randomized design (CRD) with 3 sets, 4 replications and 8 treatments. These treatments consisted of control, single and combined applications of B. japonicum USDA 110, endophytic Streptomyces sp.; P4 isolate and nitrogen fertilizer. For nodulation, it was found that the use of B. japonicum USDA 110 with endophytic Streptomyces sp.; P4 isolate could significantly improve the shoot, nodule and total dry weights of soybeans (P<0.05) at growth (V6) and flowering stages (between R3 and R4), especially the nodule dry weight at V6 (P<0.01). It had no effect on root dry weight at both growth stages. It could also significantly improve the relative ureide index, percentage of seasonal fixed nitrogen, total nitrogen accumulation and amount of fixed nitrogen (P < 0.01) for nitrogen fixation. At harvesting stage, the number of pods per plant, seeds per pod and seed yield of soybeans in all treatments did not differ statistically. The results of this study indicated the possibility of using endophytic Streptomyces sp.; P4 isolate with Bradyrhizobium japonicum USDA 110 to promote nodulation, nitrogen fixation and yield of soybeans.