Substituting inorganic nitrogen with organic inputs improves yield-scaled greenhouse gas emissions and soil health indicators: evidence from a long-term fertilizer experiment

Introduction Sustainable nitrogen management must maintain cereal productivity while limiting greenhouse gas (GHG) emissions and improving soil health. We evaluated whether partial inorganic-N substitution affects cereal productivity and GHG emissions differently across organic input types in a long-term fertilizer experiment. Methods Eight nutrient-management treatments were evaluated in a fixed-plot experiment established in 2002. Four integrated nutrient-management treatments replaced 25% of Soil Test Crop Response (STCR)-based inorganic N with farmyard manure (FYM), vermicompost (VC), urban compost (UC), or crop residue (CR). Soil CO₂, N₂O, and CH₄ fluxes were monitored during the 2024-2025 wheat season, and post-harvest soil chemical and biological indicators and wheat yield were measured. Results Relative to 100% STCR-based NPK, FYM and UC reduced cumulative N₂O-N emissions by 31% and 26%, respectively, whereas VC and CR increased them by approximately 24% and 21%. Treatment effects on cumulative CO₂-C and CH₄-C fluxes were not significant, and all treatments were small net CH₄ sinks. Organic-containing treatments increased soil organic carbon from 0.49% in the control to 0.55%-0.87%. FYM substitution produced the greatest grain yield (5,388 kg ha⁻¹), 13% above 100% STCR-based NPK. Discussion Long-term nutrient management influenced soil-health indicators and wheat yield, but the reported GHG emissions represent only the 2024-2025 wheat season. Yield-scaled GHG responses depended on organic-input quality and were not uniformly improved by substitution. Locally available, quality-controlled FYM or UC may reduce N₂O intensity, subject to material cost, labor, availability, and competing uses.