Enhancing soybean (Glycine max M.) productivity through synergistic application of hormones and nutrients synergy

Soybean is a vital global legume crop, yet its productivity is often constrained by nutrient limitations, suboptimal physiological efficiency, and limited access to growth-enhancing technologies. Although plant growth regulators (PGRs) and nutrients individually improve growth, their combined effects on soybean physiology and yield remain poorly understood. Hence, there is a critical need to evaluate integrated PGR–nutrient strategies to enhance soybean productivity and sustainability under field conditions. This study evaluated the synergistic effects of foliar-applied plant growth regulators (PGRs) viz., Gibberellic acid (GA₃) and melatonin, and/or combined with a micronutrient-enriched spray (DAP, MnSO₄, FeSO₄, and ammonium molybdate) on soybean performance under field conditions in Tamil Nadu Agricultural University, Coimbatore during Kharif season of 2023. Six foliar treatments including control, nutrients, GA₃, nutrients with GA₃, melatonin, and nutrients with melatonin were applied at 30 and 40 DAS and evaluated in a randomized block design to assess growth, photosynthetic efficiency, biochemical traits, and yield components. The combined application of melatonin and nutrients (T6) significantly enhanced plant height, leaf area, chlorophyll content, nitrate reductase activity, and seed yield per plant (19.6 g), outperforming the other treatments. Melatonin alone (T5) yielded the highest seed protein content (37.58 mg/g), thereby highlighting its role in nutritional enhancement. The results demonstrate that integrating PGRs with nutrient optimize soybean metabolism, reproductive success, and seed quality offering a scalable strategy for sustainable legume intensification.