Identifying optimal straw return strategies for crop production using meta-analysis and interpretable machine learning

Straw return is widely promoted to improve soil fertility and crop productivity, but its climate consequences remain uncertain because yield gains may be accompanied by increased greenhouse gas (GHG) emissions. A total of 5570 observations from published field studies were synthesized to quantify global responses of crop yield, N₂O, CO₂, CH₄, global warming potential (GWP), and greenhouse gas intensity (GHGI) to straw incorporation. Extreme Gradient Boosting, Shapley additive explanations, and bootstrap analysis were integrated to identify the dominant drivers and management thresholds for balancing productivity and climate impacts.

Straw return increased crop yield by 5.02%, but also increased N₂O emissions by 12.64%, CO₂ emissions by 31.39%, and CH₄ emissions by 34.85%, resulting in increases of 57.30% in GWP and 80.94% in GHGI. These responses were strongly regulated by crop type, straw-return rate, incorporation depth, return duration, fertilization, and climatic conditions. Straw-return rate was the dominant predictor of N₂O emissions, whereas mean annual precipitation was the primary predictor of CO₂ and CH₄ emissions. Management practices involving a straw-return rate of approximately 5 t ha⁻¹, a return duration of 1-3 years, and the use of maize or wheat straw rather than rice straw were associated with a more favorable balance between crop yield and GHG emissions. Estimated agronomic thresholds for fertilization were 180 kg N ha^-1, 75 kg P₂O₅ ha^-1, and 180 kg K₂O ha^-1, whereas environmental thresholds for limiting GWP and GHGI were 210 kg N ha^-1, 40-100 kg P₂O₅ ha^-1, and 100 kg K₂O ha^-1.

These findings demonstrate that straw return is not universally beneficial for the climate but can be optimized through crop-specific and climate-adapted residue and nutrient management. The study provides global quantitative evidence for designing climate-smart straw-return strategies that reconcile food production with GHG mitigation across agroecosystems. © 2026 Society of Chemical Industry.