Abstract
Nitrous oxide (N₂O) is a potent greenhouse gas contributing to climate change, and rice-wheat cropping systems are significant sources. This study investigated the effects of three irrigation methods—continuous flooding (CF), alternate wetting and drying (AWD), and drip irrigation (DI)—on N₂O emissions, crop yields, and yield-scaled emissions in a rice-wheat rotation over two years in the Indo-Gangetic Plain. Field experiments were conducted using a randomized complete block design with three replicates. N₂O fluxes were measured weekly using static chamber-gas chromatography. Results showed that cumulative N₂O emissions were highest under CF (2.85 kg N ha⁻¹ yr⁻¹), intermediate under AWD (2.12 kg N ha⁻¹ yr⁻¹), and lowest under DI (1.48 kg N ha⁻¹ yr⁻¹). However, rice grain yields were significantly lower under DI (5.2 t ha⁻¹) compared to CF (6.8 t ha⁻¹) and AWD (6.5 t ha⁻¹), while wheat yields were similar across treatments. Yield-scaled N₂O emissions (g N₂O-N kg⁻¹ grain) were lowest under AWD for rice (0.18) and under DI for wheat (0.12). Soil moisture and temperature were key drivers of N₂O fluxes, with emissions peaking after nitrogen fertilization and rewetting events. Our findings suggest that AWD offers a balanced trade-off between mitigating N₂O emissions and maintaining crop productivity in rice-wheat systems. Drip irrigation may be viable for wheat but requires optimization for rice to avoid yield penalties. These results provide evidence for policymakers and farmers seeking sustainable irrigation practices to reduce greenhouse gas emissions while ensuring food security.