Straw return reshapes soil organic carbon stability: A global meta-analysis.

Area of Science:

• Agricultural Science
• Soil Science
• Environmental Science

Background:

• Straw return is a common practice for enhancing soil organic carbon (SOC) sequestration and mitigating climate change.
• The specific impacts of straw return on different SOC pools, particularly particulate organic carbon (POC) and mineral-associated organic carbon (MAOC), require further elucidation.
• Understanding the dynamics of various SOC fractions (e.g., dissolved organic carbon (DOC), easily oxidizable organic carbon (EOC), microbial biomass carbon (MBC), microbial necromass carbon (MNC)) is crucial for a comprehensive assessment.

Purpose of the Study:

• To conduct a meta-analysis evaluating the responses of POC and MAOC to straw return.
• To comprehensively assess the variations in other SOC pools under straw return conditions.
• To identify key environmental factors and soil properties influencing POC and MAOC accumulation.

Main Methods:

• Meta-analysis of existing studies on straw return effects on soil organic carbon pools.
• Examination of variations in POC, MAOC, DOC, EOC, MBC, and MNC.
• Linear regression, Shapley additive explanation (SHAP), and structural equation modeling (SEM) analyses.

Main Results:

• Straw return significantly enhanced most SOC pools, with notable increases in POC (35.73%), EOC (41.17%), and MNC (35.59%).
• Straw return decreased the MAOC/SOC ratio and increased EOC, indicating reduced SOC stability.
• POC and MAOC accumulation were negatively correlated with initial soil total nitrogen (TN) and mean annual precipitation (MAP); specific thresholds were identified for TN and sand content influencing POC.

Conclusions:

• Straw return primarily increases the labile POC pool, potentially limiting its overall contribution to stable SOC sequestration.
• MAOC plays a dominant role in SOC sequestration under straw return, with its accumulation influenced by soil pH, straw return duration, and potential evapotranspiration (PET).
• Integrating additional agricultural practices alongside straw return may be necessary to optimize SOC sequestration efficacy.