Meta-analysis of the accumulation and stabilisation of particulate and mineral-associated organic carbon by fertilization

Fertilization is a crucial factor influencing soil organic carbon (SOC) accumulation. While the effects of fertilization strategies on SOC sequestration have frequently been investigated, their impacts on mineral-associated organic carbon (MAOC) and particulate organic carbon (POC) accumulation and their global distribution patterns remain unclear. We conducted a meta-analysis of 870 observations to assess the effects of fertilization on soil C fractions and their stability and identify the main drivers. Fertilization increased MAOC and POC contents by 18 % and 68 %, respectively, while reducing the ratio of MAOC to SOC by 10 %. Co-application of mineral and organic fertilisers led to the most significant increases in MAOC (30 %) and POC (125 %) contents. Significant increases in SOC pools occurred in arid regions with low soil C/N ratio, low clay content, high soil pH (≥7.3), and fertilization duration exceeding 10 years. The increase in alkyl C, carbonyl C, and carboxyl C and a decrease in O-alkyl C in soil organic matter under fertilization indicate a shift toward more stable molecular structures, reflecting the increased SOC stability. SOC responses to fertilization were enhanced in mid-latitude to high-latitude regions compared to lower latitudes. In conclusion, under fertilization, SOC accumulation is primarily driven by POC increases and greater molecular structural stability of SOC; this offers crucial insights for understanding soil carbon sequestration under agricultural management.