A Preliminary Study of USDA 110 (Bradyrhizobium diazoefficiens) Strain Nodulation Performance and Soybean Growth Under Water Scarcity Conditions

Nitrogen fixation is one of the key benefits of the economic and environmentally sustainable approach that legumes contribute to crop production. With the fruitful cooperation of legume-rhizobia symbiosis, soybean cultivation contributes to this sustainability while drought threatens this sustainable agricultural system. Thus, this study aimed to verify the influence of water deficit on the soybean nodulating performance concerning different inoculants, crop growth and quality. A field experiment was conducted to determine the effects of irrigated and water scarcity conditions (full: WHC 100% and deficit: WHC 50%) on soybean yield and quality and also to test the nodulation performance of two different inoculants USDA 110 (Bradyrhizobium diazoefficiens) and Azotek (Rhizobium spp.) applied to 3 different soybean cultivars (Umut-2002, Cinsoy and Altınay). For this purpose, plant height (cm), first pod height (cm), number of pods per plant, 1000 seed weight (g), seed yield (kg ha-1), SPAD chlorophyll content, leaf area (cm2), crude protein and oil content (%) traits were measured. According to the field and root observations, no nodulation history was observed in both Rhizobia strains under irrigated and water scarcity conditions. Water limitation resulted with the negative impact on soybean yield (≈35% less) and yield formation. In addition to yield reduction, water scarcity caused a significant decrease in SPAD chlorophyll content in the reproductive stages and leaf area of the plant. As a result of this preliminary study, water scarcity has irreversible effects on soybean plant physiology and yield formation in the hot climate conditions of Aydın province. Further field studies are needed to observe the nodulation performance of soybean plants in the region which has not been observed in the field studies so far.