Life Cycle Assessment of Wheat Production under Variable Tillage and Nitrification Inhibitor Management: Implications for N₂O Mitigation and Energy Efficiency

Sustainable wheat production is critical to meet increasing global food demand while minimizing environmental impacts and enhancing energy efficiency. This study investigated the effects of nitrification inhibitors (NIs) and tillage practices on soil NH₄⁺, NO₃⁻, and N₂O emissions, the abundance of ammonia-oxidizing archaea (AOA) and bacteria (AOB), wheat yield, environmental impacts, and energy use in semi-arid wheat systems in Iran. A field experiment was conducted with two tillage systems: no-tillage (NT) and conventional tillage (CT), and three fertilizer treatments: urea (UR), urea plus nitrification inhibitor (NIU), and control (CO). NI application significantly reduced N₂O emissions by 22.32% under NT and 12.06% under CT, while suppressing NH₄⁺ and NO₃⁻ nitrification across all growth stages. AOB abundance was more responsive to NI than AOA, particularly in CT soils with higher pH. NT practices enhanced soil organic matter, improved nitrogen-use efficiency, and decreased field operational emissions. Life Cycle Assessment (LCA, ReCiPe 2016) indicated that NT reduced global warming potential (2,093.32 vs. 2,676.51 kg CO₂-eq), human health impacts (0.00748 vs. 0.00901 DALY), and resource use (51.20 vs. 73.90 USD ha⁻¹) compared to CT, though terrestrial (13,506.52 vs. 13,132.73 kg 1,4-DCB) and freshwater ecotoxicity (1,429.36 vs. 1,222.57 kg 1,4-DCB) increased slightly due to higher herbicide and insecticide reliance. Energetic analysis revealed that NT achieved higher total output energy (181,847.96 vs. 168,617.94 MJ ha⁻¹), energy ratio (11.67 vs. 7.32), energy productivity (0.453 vs. 0.284 kg MJ⁻¹), reduced energy intensity (2.21 vs. 3.53 MJ kg⁻¹), and greater net energy gain (166,285.57 vs. 145,593.52 MJ ha⁻¹) than CT. Overall, combining NIs with NT enhances wheat yield, reduces N₂O emissions, and improves both environmental and energy efficiency, demonstrating a practical strategy for sustainable cereal-based production in semi-arid regions.