Long-Term Organic Amendments Combined with Nitrogen Fertilization Regulates Soil Organic Carbon Sequestration in Calcareous Soil

Organic amendments have been widely confirmed to support soil health and agricultural sustainability. However, the effects mechanisms of long-term organic combined with chemical fertilizers on carbon (SOC) sequestration macroaggregate formation are still unclear. Therefore, this study aimed explore interaction between agglomeration after 12 years fertilization. Seven treatments within a field experiment were selected conduct research, including nitrogen (N) application by farmers, optimized N management, biochar and/or straw, manure, compost or biogas residue plus management. The results showed that addition materials significantly enhanced SOC 29.6–119.8% 10.3–36.3% in 0–15 15–30 cm layers compared respectively. Meanwhile, humus pools layer increased 14.7–205.2%, particularly humin (HUC), which could be considered as useful indicator process. Among materials, was most effective strategy due its high aromatic content resisted biodegradation. also improved labile fractions, contents microbial biomass (MBC), dissolved (DOC), particulate (POC) KMnO4-oxidizable (ROC) 120.5%, 92.3%, 217.2% 85.5% average, respectively, amount exchangeable Ca2+ Mg2+ cations Fe Al oxides whilst Na+ declined layer. These indicators significant correlation mean weight diameter (MWD). Our revealed an management practice promote calcareous soil.