Modelling N2O Emissions and Yield Responses under Drip Fertigation and Future Climate Scenarios with DNDCv.CAN

Drip fertigation can conserve water in arid and semi-arid regions across the world. Recent field studies have shown that drip fertigation can also mitigate emissions of the powerful greenhouse gas nitrous oxide (N₂O). However, existing process-based models have not been evaluated for simulating N₂O emissions under drip fertigation systems, limiting our capacity to predict the environmental performance of these irrigation technologies under future climatic conditions. Here we assessed the performance of the Canadian version of the DeNitrification-DeComposition model (DNDCv.CAN) in simulating N₂O emissions from drip-fertigated maize systems. The model was calibrated and validated using a comprehensive two-year dataset from a field experiment in Spain that included subsurface and surface drip irrigation with four nitrogen (N) fertigation treatments: ammonium sulfate (AS), AS with nitrification inhibitor DMPP (AS_DMPP), calcium nitrate (CN), and a control without N (N0). The calibrated model accurately simulated crop yield (RMSE < 1,300 kg ha⁻¹), grain N content (RMSE < 12 kg N ha⁻¹), and cumulative N₂O emissions (RMSE < 0.03 kg N ha⁻¹), with R² values of 0.6-0.8 and d-index above 0.8. Under future climate scenarios, both surface and subsurface drip irrigation will likely experience yield reductions and increased N₂O emissions. Subsurface drip showed slightly lower yield losses but higher N₂O emissions compared to surface drip irrigation. CN-based fertilizer integrated with subsurface drip performed best, achieving both higher yields and lower N₂O emissions. Increasing heat stress is likely the primary factor driving the yield losses. Adaptation strategies focused on mitigating heat stress should be explored to support the use of drip fertigation systems in arid and semiarid regions.