Biological and inorganic fertilizer applications improved growth, nodulation and yield of soybean (glycine max l.) Varieties

The increasing costs of inorganic fertilizers and their effect on the environment have resulted in an ever increasing interest in the role of biological fertilizers as a source of plant nutrients and soil fertility restoration. In this regard, identifying varieties which adapt to growing areas and agronomic inputs such as bio-fertilizer and optimum phosphorus rates could potentially improve soil fertility and productivity of legumes including soybean. Therefore, this study was conducted to evaluate the effect of Bradyrhizobium inoculation and phosphorus application on growth, symbiotic and yield performance of soybean varieties grown at Assosa, Western Ethiopia. The treatments included three soybean varieties (Gizo, Belessa-95 and Local), two inoculation levels (uninoculated and inoculated with Bradyrhizobium strain; MAR-1495) and three phosphorus levels (0, 10 and 20 kg P ha-1). The experimental units were arranged using factorial randomized complete block design with three replicates. The results revealed marked varietal differences on growth, yield and yield components. Of the three soybean varieties Belessa-95 showed better response for nodule number, nodule dry weigh, plant height, shoot dry weight, hundred seed weight and grain yield when compared to Gizo and Local varieties. The inoculation with Bradyrhizobium strain MAR-1495 and application of higher P rates (20 kg P ha-1) resulted in marked improvement on most of the studied parameters. For instance, the highest yield (2.31, 2.70 and 2.53 ton ha-1) was recorded with the variety Belessa-95, the application of 20 kg P and Bradyrhizobium inoculation, respectively. It could, thus, be deduced that the use of Bradyrhizobium strain MAR-1495 and Belessa-95 variety with application of 20 kg P ha-1 markedly improved the yield and related components, and which in turn improves the nutrition and food security of small scale farmers in the study area.