Effect of long-term organic fertilization on soil chemical, biological properties and labile organic carbon fractions under maize (Zea mays L.) cultivation

Abstract Organic fertilization has been known to improve soil health by accelerating microbial activity, which mainly regulated the formation and decomposition of labile organic carbon (LOC). The objectives of this study were to: (1) analyze the effects of different fertilization on soil microbial activity; β-glucosidase, dehydrogenase, phosphatase, urease and soil respiration (RES) and LOC; particulate organic carbon (POC), permanganate oxidizable carbon (POXC), and microbial biomass carbon (MBC), and (2) evaluate the potential of LOC pool as a soil health indicator through correlation analysis. Treatments included chemical fertilizer (NPK), cattle manure compost (COM), green manure crops (GM), and an unfertilized control (NF). Soil chemical properties and microbial activity were higher in organic resource treatments (COM, GM) than in NPK. The COM treatment showed the highest values for pH, total nitrogen (T-N), soil organic matter, available phosphorus, and exchangeable cations. Also, microbial enzyme activities (β-glucosidase, dehydrogenase, phosphatase, urease) and RES were higher in organic fertilization, compared to NPK. In particular, COM treatment increased urease activity and respiration by 35% and 60%, respectively, relative to NPK. Significant positive correlations were observed between soil microbial activity and the LOC fractions, in particular, POC showed the strongest correlation ( p < 0.01). Particulate organic C could be suggested as a reliable indicator for soil health. Additionally, maize yield of the organic treatments was comparable to those of NPK, confirming organic fertilization could be an effective management for both soil health and crop yield.