Effect on greenhouse gas emissions (CH4 and N2O) of straw mulching or its incorporation in farmland ecosystems in China

Straw returning can enhance crop yield, promote soil organic carbon sequestration, and support sustainable crop production. However, straw management techniques, such as straw mulching (SR-M) and straw incorporation (SR-I), can significantly elevate greenhouse gas (GHG) emissions. This meta-analysis synthesizes data from 217 studies to explore the effects of different straw management approaches on mitigating GHG emissions in agricultural settings. The analysis reveals that SR-I (129.39 %) had a more pronounced impact on CH4 emissions than SR-M (14.86 %), but SR-M (18.47 %) had a more significant impact on N2O emissions than SR-I (7.76 %). Notably, SR-I had a greater impact on soil carbon content than SR-M. The effect of straw returning on CH4 and N2O emissions varied under different climatic conditions, management practices, and initial soil properties. Specifically, under conditions characterized by a mean annual temperature (MAT) ≤ 14 °C, mean annual precipitation (MAP) > 800 mm, initial soil organic carbon (SOCi) ≤ 14 g kg−1, initial soil total nitrogen (TNi) ≤ 1.2 g kg−1, and soil pH > 6, with straw returning amounts (SRA) ≤ 6000 kg ha−1, nitrogen application rate (NAR) > 200 kg ha−1, straw returning duration > 3 years, and maize, rice, wheat–maize, or wheat–rice as the cultivated crop, SR-M had a lesser impact on CH4 and N2O emissions than conditions under other environmental and management measures. Under conditions characterized by MAT ≤ 14 °C, MAP ≤ 800 mm, SOCi > 14 g kg−1, TNi > 1.2 g kg−1, and soil pH > 8, with SRA > 6000 kg ha−1, straw returning duration > 3 years, and wheat as the cultivated crop, SR-I had a lesser impact on CH4 and N2O emissions than conditions under other environmental and management measures. Furthermore, deep straw incorporation (SR-Ideep, straw mixed with 20–40 cm deep soil) did not significantly affect CH4 and N2O emissions, suggesting its potential for widespread adoption. These findings offer valuable insights for optimizing straw management practices and reducing GHG emissions in farmland ecosystems.