Trade-offs and synergies of integrated nitrogen–sulfur management for sustainable Indian mustard: yield, profitability, and soil resilience under semi-arid conditions

Sulfur (S) is becoming increasingly widespread in Indian agricultural soils because of intensive cropping, declining organic matter, reduced atmospheric deposition and leaching losses, thereby limiting oilseed productivity and soil health. Although micronized sulfur fertilizers offer improved nutrient synchronization, information on their optimum source, rate, and application timing remains limited. A two-year field experiment was conducted to evaluate micronized sulphonated urea formulations (US-I and US-II), applied either as basal or split, in comparison with ammonium sulfate, bentonite sulfur, single superphosphate and sulfur-unfertilized control in Indian mustard. Sulfur uptake followed a distinct temporal pattern, with 8-12% during early vegetative growth, 50-60% from the early vegetative stage to flowering, and 30-40% from flowering to seed filling, highlighting the importance of sustained sulfur availability during reproductive growth. Split application of US-II and US-I significantly improved sulfur availability, nutrient-use efficiency, microbial biomass carbon, dehydrogenase and arylsulfatase activities, and maintained balanced soil nitrogen dynamics compared with conventional sulfur sources. These improvements resulted in the higher nitrogen- and sulfur-use efficiency (48.3 and 24.3%, and 47.5 and 23.0%, respectively), seed yield (2.76 and 2.74 Mg ha -1 ), and net returns ($1323 and 1277 ha -1 ) under split application of US-II and US-I, respectively. Overall, synchronizing sulfur supply with crop demand through split application of micronized sulphonated urea enhanced crop productivity, nutrient-use efficiency, profitability, and soil biological functioning. This strategy provides an effective approach for improving sulfur management and promoting sustainable Indian mustard production in semi-arid agroecosystems.