Shifts in biomass allocation shape yield responses of mung bean (Vigna radiata L.) to molybdenum and silicon

Abstract Nutrient limitation is a persistent constraint to mung bean in low-input cropping systems, where micronutrient availability plays a critical role in nodulation, biomass allocation, and yield. This study examined the individual and combined effects of molybdenum (Mo) and silicon (Si) on growth, root–nodule, and yield of Vigna radiata L. grown under nitrogen-limited soil conditions. A pot experiment was conducted using a completely randomized design with four treatments: control, Si, Mo, and combined Si + Mo. Plant height was not influenced by micronutrient application, indicating limited effects on shoot elongation. In contrast, Mo substantially improved belowground development, resulting in greater root biomass, increased nodule fresh weight, and higher seed number and seed yield compared with the control. Si alone significantly altered root traits and nodulation, demonstrating its capacity to modify belowground allocation. The combined Si + Mo promoted greater allocation to root and nodule biomass relative to individual treatments; however, this response was accompanied by reduced pod number and seed yield relative to Mo alone, indicating an imbalance in assimilates partitioning. Correlation and principal component analysis provided clear insight into traits, that Mo-treated plants were closely associated with yield-related parameters, whereas the combined Si + Mo aligned with root biomass and nodulation. Overall, the findings indicate that Mo is a key micronutrient for optimizing nodulation and reproductive performance of mung bean, while silicon plays a direct role in shaping root and nodule development.