Response of Soybean to Inoculation with Bradyrhizobium spp. in Saline Soils of Shinille Plains, Eastern Ethiopia

Abstract

Soybean [Glycine max (L.) Merrill] is an important crop in Ethiopia. However, its productivity is  constrained by a number of factors among which soil salinity is one the major problems. Therefore, field  and greenhouse experiments were conducted to examine the effectiveness of exotic and locally isolated  Bradyrhizobium spp. nodulating soybean in a saline soil containing high soil N in Shinille area, Somali  region, Ethiopia. The treatments of the glasshouse experiment consisted of effective isolates of  bradyrhizobia nodulating soybean (TAL-379, UK isolate, and isolate) and an improved genotype of  soybean. The treatments of the field experiment consisted of three bradyrhizobia isolates and control  check. All treatments were replicated three times. The results of the experiments showed that  inoculation significantly improved nodulation, growth, and productivity of soybean over the control  treatment. Among the inoculation treatments, isolate and UK isolate inoculation significantly (P < 0.05) improved the nodulation and grain yield of soybean over the TAL-379 treatment. All investigated traits,  except grain yield, did not display significant differences in response to the inoculation treatments. This  indicates soil properties measured and evaluated at the late stages of growth of the crop especially native  soil nitrogen content was high. The regression analysis indicated significant association of nodule number and nodule dry weight with highest R2 scored in isolate inoculation. The multiple regression  analysis revealed that nodulation and plant tissue nitrogen concentration had strong relationships with  grain yield, indicating the importance of symbiotic nitrogen fixation. Hence, inoculation of elite isolate of  Bradyrhizobium sp. improved the yield of the soybean in saline soils. Although Bradyrhizobium inoculation improved remakablely the productivity of soybean, the yield gap is still very wide as compared to the  potential yield reported elsewhere. Therefore, further research is required to improve the yield of the crop by diagnosing othr soil constraints in the region.

Keywords: Glycine max (L.) Merrill; Grain Yield; Inoculation; Isolate; Nodule Number; Nodule Dry Weight; Saline Soils