Nitrogen and organic matter managements improve rice yield and affect greenhouse gas emissions in China’s rice-wheat system

Abstract

Context

Mineral nitrogen (N) management and organic matter management in the paddy fields directly affect yield and soil greenhouse gas (GHG) emissions in the rice-wheat rotation system of China. However, comprehensive research on the combined impacts of these two practices remains insufficient, and there is a lack of quantitative analyses on a large regional scale as well as identification of the main drivers.

Objective

This study aimed to elucidate the impact of mineral N management and organic matter management on rice yield and global warming potential (GWP) and their spatial distribution patterns, and to investigate influential factors.

Methods

We combined machine learning algorithms based on meta-analysis to assess the effect of mineral N management (synthetic N fertilizer, slow-/controlled- release fertilizer) and organic matter management (organic fertilizer, biochar amendment, and straw return) on rice yield and GHG in the rice-wheat system by compiling 163 peer-reviewed journal articles and high-resolution multi-source databases in China.

Results

Mineral N management significantly increased rice yield (412 %) and N₂O (162.3 %), and reduced GHG emissions intensity (GHGI; 20.1 %). Organic matter management increased CH₄, GWP, and GHGI by 74.4 %, 60.8 %, and 55.1 %, respectively. Machine learning (random forest (RF), support vector machine, multiple layer perceptron, and gradient boosting machine) suggested that RF was the optimal method for predicting rice yield and GHG (R² = 0.43–0.90). The spatial distribution indicated that mineral N management boosted rice yield and N₂O while reducing GHGI, especially in the Middle-lower Yangtze River (MLY) region, by 37.6 %, 277 %, and 25.2 %, respectively. Structural equation modeling and RF analysis revealed that field management practices and edaphic factors had major contributions to rice yield, while climatic factors were positively with CH₄ and N₂O emissions.

Implications

Our findings provide insights into the importance of inorganic and organic managements to ensure food security and environmental sustainability, thereby contributing to the promotion of sustainable rice production.