Assessment of Nitrogen Fixation by Mungbean Genotypes in Different Soil Textures Using 15N Natural Abundance Method

Ensuring food and nutritional security in light of high climate variability and a rapidly growing population remains a challenge. Mungbean (Vigna radiata (L.) Wilczek) is a short duration, drought-tolerant, and ureide-exporting legume crop capable of symbiotic atmospheric nitrogen fixation. Estimates of biological N2 fixation by mungbean in different soil textures have not been extensively studied. We conducted this study to evaluate plant growth and N2 fixation of five mungbean genotypes (Berken, 8735, IC 8972-1, STB#122, 223) inoculated with Bradyrhizobium spp. and grown on loamy sand and silt loam soils under glasshouse conditions. Mungbean dry matter yield, δ15N values, shoot content, amounts of N-fixed, and soil N uptake were all higher on the silt loam soil compared to the loamy sand soil, demonstrating the effects of soil properties on plant growth and N2 fixation potential. Among genotypes, IC 8972-1 produced the highest biomass (7.85 g plant−1), shoot N content (200 mg plant−1), and soil N uptake (155 mg plant−1) than other genotypes. The significant interaction between soil texture and genotypes for root dry matter and %Ndfa indicates the major role of legume root-nodule bacteria in symbiotic N2 fixation. This study demonstrated that N2 fixation in mungbean is affected by both genotypes and soil properties, illustrating the need to consider soil properties in order to maximize N contribution from mungbean to agricultural production systems.