Energy Budgeting, Carbon Footprint and Multi-Criterion Sustainability Assessment of Long-Term Organic Nitrogen Management in a Rice–Wheat Cropping System of the Indo-Gangetic Plains

Organic nitrogen sources have been widely adopted for rice–wheat cropping systems (RWCSs) of the Indo-Gangetic Plains, but their combined energy, greenhouse-gas and economic performance is rarely assessed. In a fixed-plot experiment at the ICAR Indian Agricultural Research Institute, New Delhi, in which the same treatments have been applied since 2002, we compared six organic nitrogen treatments, from an unfertilized control (T1) to green manure plus farmyard manure (FYM) plus biofertilizer (T6). Yield, energy, greenhouse-gas and economic data came from the two most recent rice–wheat cycles; soil organic carbon was measured after the final wheat harvest. Organic inputs raised rice-equivalent yield by 20–50% and total organic carbon by 53–77% relative to the control but increased energy input up to 4.3-fold, so energy-use efficiency fell from 16.4 to 5.3–9.0. The field-scale, gate-to-gate carbon footprint (yield-scaled N2O, CH4, and CO2 emissions) was the lowest in the control (0.27 kg CO2-eq kg−1 grain), the lowest among the amended treatments in green manure plus biofertilizer without FYM (T4; 0.31), and the highest with FYM (0.43–0.48). T4 also had the highest benefit–cost ratio (10.6), and the FYM treatments had ratios of 1.2–1.7 at the recorded FYM price, but this disadvantage depended strongly on the FYM price. A TOPSIS ranking based on five non-redundant criteria placed T4 first; T4 ranked first in 59% of random weight sets and in 89% of uncertainty simulations, with the control being its main competitor. An exploratory data envelopment analysis found no FYM-based treatment to be efficient. Nutritional output increased steadily with organic input and was the highest in T6. Under the conditions of this experiment and the criteria selected, green manure plus biofertilizer offered the most favourable compromise among productivity, efficiency, greenhouse-gas intensity and profitability, whereas FYM-based systems maximized yield and soil carbon at higher calculated energy input and cash cost.