Israel M. Guanzon, Keanne Joy S. Rivera
Soybeans are renowned for their high-quality protein content and vital role in global food and feed production. Enhancing its productivity through strategic agronomic practices, particularly inoculation and fertilization, is essential, especially in marginal soils. This study evaluated the efficacy of Bradyrhizobium sp. and foliar application of molybdenum (Mo) on soybean biomass and yield under lahar sediment conditions in Porac, Pampanga, Philippines, from January to April 2024. A randomized complete block design with four treatments: control, Bradyrhizobium sp., Mo (40 g ha −1 ), and a combination of Bradyrhizobium sp. + Mo, was implemented with three replications. Results indicated that the combined application of Bradyrhizobium sp. + Mo significantly enhanced shoot biomass (67.2%), crop growth rate (35.8%) and root length (66.0%) relative to the control. In contrast, root-to-shoot ratio and distribution index were not significantly affected, while dry matter efficiency (5.38 g m −2 day −1 ) and harvest index (0.39) declined under combined. Agronomic traits improved markedly, with pod number and hundred-seed weight increased by 92.8% and 50.0% respectively, when combined treatments were applied during the R1 (initial flowering) and R2 (full bloom) stages. The highest yield (2.06 ton ha −1 ) was obtained from Bradyrhizobium sp. + Mo treatment, which was significantly higher than the control. Seed yield exhibited strong correlated with seed production efficiency, which increased by 46.25%, reflecting an efficient biomass conversion into seed yield. Therefore, integrating Bradyrhizobium sp. and foliar Mo application substantially improved soybean biomass and yield under marginal lahar conditions, demonstrating its potential as a sustainable strategy for improving productivity.