Soil-borne diseases, including charcoal rot (Macrophomina phaseolina) and collar rot (Sclerotium rolfsii), threaten global soybean production. Four fungicide combinations were tested as seed treatments at three concentrations (1, 1.5, and 2 g or ml per kg of seed) under controlled conditions to address the challenges posed by these diseases. Under controlled conditions, the combination of thiophanate methyl + pyraclostrobin at a rate of 2 mL/kg of seed significantly alleviated disease symptoms caused by both pathogens. Additionally, it enhanced shoot and root weights by over 50% in plants affected by S. rolfsii. Field trials were conducted for two years at two distinct locations to assess the efficacy of three selected combination seed treatment fungicides against M. phaseolina and S. rolfsii. Both inoculated and uninoculated controls were included for the comparison. Among the fungicides, thiophanate-methyl + pyraclostrobin and trifloxystrobin + penflufen proved the most effective for suppressing both diseases under epiphytotic field conditions across the years and locations. This study also highlighted the benefits of these chemical combinations in enhancing agronomic traits, maintaining yield, and ensuring the economic viability of soybeans.

The study used the DSSAT model to assess potential soybean yields in different regions of India and validated it under diverse agroecological conditions. The average simulated yield under irrigated conditions was 3794 kg ha⁻¹ relative to the simulated average rainfed yield of 2446 kg ha⁻¹, showing a 35.52% reduction in grain yield due to adverse moisture conditions under rainfed conditions. Relative to simulated yield, the average observed (actual) rainfed yield across 43 districts of India was 1025 kg ha⁻¹, which was 2769 and 1421 kg ha⁻¹ lower than irrigated and rainfed potential yield, respectively. A significant positive correlation was observed between simulated water non-limited yield and solar radiation (R² = 0.55, p ≤ 0.05). The simulated rainfed grain yield (R² = 0.66, p ≤ 0.05) had a significant, positive, and curvilinear relationship with growing season rainfall. On the other hand, the actual yield (R² = 0.008) showed a non-significant relationship with mean crop seasonal rainfall across locations. The gap between simulated yield under irrigated and rainfed conditions is huge at locations with low seasonal rainfall and narrows with increasing rainfall. In addition, the gap between actual yield and simulated yield under rainfed conditions was larger, even in high seasonal rainfall areas. The yield gap under rainfed conditions is due to the non-adoption of improved crop management practices and could be reduced with proper interventions. This includes adapting drought-resistant varieties, conserving rainwater, changing land configuration, and adopting waterlogging-tolerant varieties using improved technology to reduce the soybean yield gap.