Characteristics of Changes to POC and MAOC After Straw Returning in China: A Meta-Analysis

Abstract

Straw returning is widely practiced in China to enhance soil organic carbon (SOC). However, how it affects SOC fractions—specifically, particulate organic carbon (POC) and mineral-associated organic carbon (MAOC) remains unclear. In this meta-analysis, we synthesized 792 paired observations to assess the impacts of straw returning on SOC fractions across diverse climatic conditions, soil properties, and agronomic practices in China. The results showed that straw returning significantly increased SOC, with a larger contribution from POC than MAOC. The enhancement of POC decreased with rising mean annual temperature (MAT) and mean annual precipitation (MAP), while MAOC increased under these same conditions. Higher quantities of straw input led to greater increases in POC and MAOC. Conventional tillage had a more favorable effect on SOC, POC, and MAOC than no-tillage systems when combined with straw returning. The most substantial improvements were observed with straw returning durations between 5 and 10 years. Soils with neutral and high C/N ratios exhibited greater potential for carbon sequestration. Furthermore, optimal application rates of nitrogen (100–240 kg ha⁻¹ year⁻¹), phosphorus (110–200 kg ha⁻¹ year⁻¹), and potassium (80–160 kg ha⁻¹ year⁻¹) fertilizers maximized POC accumulation by promoting aboveground biomass and enhancing soil aggregate formation. This study provides new insights into how well-managed straw returning can improve the stabilization and functioning of soil organic carbon pools, offering a scientific foundation for developing regional straw management strategies.