Crop rotation impacts on SOC fraction contents and stability: Insights from a global meta-analysis

Abstract

Crop rotation (CR) is widely recognized as a sustainable agricultural practice that enhances soil organic carbon (SOC) accumulation and maintains soil health. However, the specific effects of CR on distinct SOC fractions and SOC stability in cropland soils remain largely unexplored. We synthesized 44 studies comprising 196 paired observations from Asia, Africa, and Europe to quantify CR effects on SOC fraction contents (particulate organic carbon, POC, and mineral-associated organic carbon, MAOC), as well as its stability across climate-soil-management contexts. Relative to continuous monocropping (MC), CR increased SOC, POC, and MAOC contents by 11.83 %, 23.56 %, and 8.57 %, respectively, and on average increased the SOC stability (indicated by POC/MAOC ratio, hereafter P/M) by 16.25 %, indicating a larger labile share at the global mean. However, subgroup analysis reveals conditions under which CR reduced the P/M ratio. Notably, CR increased SOC and its fractions but tended to reduce the P/M ratios at high temperatures and in humid regions. CR increased SOC and MAOC in acidic soils, while it enhanced POC in neutral soils relative to MC. Positive effects of CR on SOC, its fractions, and stability were observed in high initial SOC and loamy soils for POC and clayey soils for SOC, MAOC, and SOC stability. The opposite trend was observed in low initial SOC and sandy soils. The random forest results showed that changes in SOC fractions were predominantly regulated by climatic factors, while MAOC, POC, and the P/M ratio were more responsive to soil properties and agronomic practices, respectively. These findings argue for region-specific, diversified rotations paired with practices that channel inputs into MAOC to lower the P/M ratio. Incorporating the P/M ratio into monitoring, reporting, and verification complements total stock accounting by identifying systems that build durable carbon.