Straw management in paddy fields can reduce greenhouse gas emissions: A global meta-analysis

Context: Straw return is gaining popularity as a viable agricultural practice for improving soil fertility, crop yield, and produce qualityProblem: However, the inconsistent assessment of greenhouse gas (GHG) emissions from straw return in paddy fields poses a threat to both the environment and food securityObjective and methods: Therefore, a meta-analysis of 858 comparisons from 93 studies was conducted to determine the GHG emissions performance from straw return in paddy fields, identify key factors and propose the optimal straw management practices to achieve global warming potential (GWP) reductionsResults: The results indicated that straw return lowered N2O emissions (Hedges' d = -0.18, 95% CI: -0.30 to -0.06), but the benefits were fully counteracted by significant increase in CO2 (Hedges' d = 2.18, 95% CI: 1.38-2.97) and CH4 (Hedges' d = 2.82, 95% CI: 2.56-3.08) emissions, and resulting in higher GWP (Hedges' d = 2.75, 95% CI: 2.26-3.26). GHG emissions from straw return in paddy fields affected by climate and soil conditions as well as agricultural management practices, with mean annual temperature (MAT), mean annual precipitation (MAP), pH and straw size as key factors for CH4, N2O, CO2 and GWP, respectively. Additionally, GWP also influenced by MAT, MAP, soil C/N, available N, soil total N, pH, straw return method and cropping practice. Optimal GWP reduction performance was obtained when 5-10 cm straw was returned to the paddy field in region with MAP < 1338 mm. However, as climate conditions remain challenging to alter, we propose the following straw management recommendations for paddy fields: straw return amount greater than 7500 kgha(-1), with straw size >= 5 cm, and straw incorporationConclusions: Optimizing straw management in paddy fields can improve straw acceptance in paddy fields as well as mitigating the greenhouse effectImplications: This study holds implications for informing the widespread adoption of straw return practices in paddy fields by providing a scientifically grounded foundation for decision-making.