Conservation agriculture: Evaluating trade-offs and synergies in food, energy, and carbon efficiency in agri-food systems

Soil degradation, rising production costs, and increasing greenhouse gas emissions (GHGs) are major constraints to the sustainability of rice ( Oryza sativa L.)–wheat ( Triticum aestivum L.) production systems in the Indo-Gangetic Plains (IGP), where intensive tillage and imbalanced fertilizer use have resulted in yield stagnation and declining soil health. Conservation agriculture (CA), particularly zero tillage (ZT) with direct-seeded rice (DSR), has emerged as a promising approach to restore soil function and mitigate climate impacts; however, the performance of precision nutrient management strategies under such systems remains inadequately quantified. A two-year field experiment was conducted in Typic Ustochrept (sandy clay loam soil) to compare two nutrient management strategies in a zero-till rice–wheat (R-W) system - soil test based nutrient management and nutrient expert®-based nutrient management. A total of 12 nutrient management strategies were evaluated on system productivity, profitability, soil biochemical properties and food–energy–carbon footprints: balanced nitrogen, phosphorus and potassium application, nutrient omission, recommended nutrient application rates, and State recommended practices. The use of balanced soil test based NPK and Nutrient Expert® (leaf colour chart based N) resulted in higher productivity of the system by 12–18% and 28–35% over recommended fertilizer practices and net returns of 186.66–246.66 US$ ha⁻¹ and 153.33–202.66 US$ ha⁻¹, respectively. The increase of soil organic carbon (6–9%), microbial biomass carbon (14–21%) and enzymatic activities (18–27%) showed the improved soil biological functioning under the CA-strategies. Soil test based nutrient management achieved the greatest net energy gain (around 15% greater than recommended nutrient management practices) while the Nutrient Expert® strategy found a balance with a ~21% reduction in yield scaled carbon footprint, with minimal yield losses. Nutrient omission treatments also enhanced efficiency of the use of nutrients, but resulted in significant yield losses of 22–31%, indicating apparent trade-offs between yield and environmental performance. In conclusion, the combination of zero tillage and precision nutrient management has the potential to enhance soil health, profitability, and environmental sustainability, offering a promising strategy for reducing soil degradation and climate change effects while maintaining high-yielding cereal farming/production systems.