Enhancing productivity, profitability, and energy efficiency in rice–wheat systems through conservation agriculture and precision nitrogen management in the Indo-Gangetic Plains, India

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Soil degradation and declining nutritional security threaten the sustainability of the rice ( Oryza sativa L.) and wheat ( Triticum aestivum L.) production system, a cornerstone of agri-food production in South Asia. This intensive production system is increasingly constrained by low nitrogen (N) use efficiency, groundwater depletion, and high energy inputs, necessitating resource-efficient management strategies. A two-year field experiment (2022–2024) was conducted on an alluvial Inceptisol to evaluate the effects of conservation-based crop establishment and precision N management on system productivity, soil biological properties, energy use, and profitability. The experiment followed a split-plot design with three crop establishment methods—vattar direct-seeded rice- conventional-till wheat with residue retention (VDSR-CTW+R), dry direct-seeded rice-zero-till wheat with residue retention (DDSR-ZTW+R), and puddled (wet tillage) transplanted rice-conventional-till wheat without residue (PTR-CTW-R) —in main plots, and five N management strategies, including modified split application, leaf color chart (LCC)-guided N (threshold ≤3 in rice and ≤4 in wheat), and nano-urea supplementation combined with reduced mineral N (50% and 75% of recommended dose), in subplots. VDSR improved rice grain yield by 6% over DDSR, while ZTW with residue retention increased wheat yield by 7% compared with conventional tillage. LCC-guided N management enhanced rice and wheat yields by 10–12% over farmers’ practice. Substituting 25% mineral N with two foliar sprays of nano-urea maintained yields comparable to 100% recommended N, whereas 50% substitution significantly reduced yields. The DDSR-ZTW+R system achieved the highest system net returns (US$2,430–2,550 ha⁻¹), with 15–17% lower production costs and improved energy performances, reflected in higher output energy and lower specific energy use. Residue retention significantly increased soil microbial biomass carbon (6–9%) and improved root morphological traits, including length, volume, and surface area. Overall, conservation agriculture-based establishment combined with LCC-guided precision N management improved productivity, profitability, energy-use efficiency, and soil biological functioning relative to conventional practices. These findings highlight the potential of integrated conservation and precision nutrient management strategies to enhance resource-use efficiency and sustainability of rice–wheat systems in the Indo-Gangetic Plains.