Long-Term Tillage and Irrigation Management Practices: Impact on Carbon Budgeting and Energy Dynamics under Rice–Wheat Rotation of Indian Mid-Himalayan Region

In modern agriculture, reducing the carbon footprint and emission of greenhouse gases with greater energy efficiency are major issues for achieving the sustainability of agricultural production systems. To address this issue, a long-term field experiment was established from 2001 through 2016 with two contrasting tillage practices (ZT: zero tillage; CT: conventional tillage) and four irrigation schedules {I-1: pre-sowing (PS), I-2: PS + crown root initiation (CRI), I-3: PS + CRI + panicle initiation (PI)/flowering (FL), and I-4: PS + CRI + PI/FL + grain filling (GF)}. The grain yield of rice, wheat and the rice–wheat system was increased significantly by 23.6, 39.5 and 32.8%, respectively, with irrigation at four stages (I-4) compared to a single stage (I-1). Energy appraisal results exhibited that 17.2% higher energy was consumed under CT as compared to ZT (25,894 MJ ha−1). Fertilizer application consumed the highest energy (46.5–54.5%), followed by irrigation (8.83–19.5%), and the lowest energy consumption was associated with winnowing, packing and transport (2.07–2.43%) operations. The total energy output of the rice–wheat system did not change significantly among contrast tillage, but higher energy was obtained under CT (214,603 MJ ha−1) as compared to ZT (209,728 MJ ha−1). ZT practice improved the energy use efficiency (EUE), energy productivity (Ep) and energy profitability (Eprof) by 16.6, 21.0 and 16.6%, respectively, over CT. The EUE, SE (specific energy), Ep, net energy return (NER) and Eprof were enhanced by 17.1, 16.6, 21.0, 36.5 and 20.6%, respectively, with irrigation at four stages (I-4) compared to a single stage (I-1). Zero tillage plots reflected a 8.24% higher carbon use efficiency (CUE) and a 9.0% lower carbon footprint than CT plots. Among irrigation schedules, application of I-4 showed a 8.13% higher CUE and a 9.0% lower carbon footprint over single irrigation (I-1). This investigation indicated that ZT with irrigation at four stages (I-4) was the most sustainable option for improving the EUE and CUE with minimal GHGs emissions from the rice–wheat cropping system of Indian mid-Himalayan regions.