Effects of long-term fertilization on soil active organic carbon and soil enzyme activities in upland red soils
长期施肥对红壤旱地土壤活性有机碳和酶活性的影响

Soil fertility is important for the sustainable development of red soil agroecosystem. In this paper, soil microbial biomass, soil active organic carbon, carbon management index (CMI) and soil enzymes activities were studied in upland soils under different fertilizer applications in a 21a long-term fertilization experiment. Results showed that soil pH, CEC, SOC, total N, total P, mineral N, available P, available K and soil microbial biomass in manure fertilization treatments (NPK+OM and OM) all increased significantly compared with no fertilization (CK) and mineral fertilization treatments (N, P, K, NP, NK, NPK and 2NPK). The active organic carbon and carbon management index also significantly increased and more than the original soil and other fertilization treatments. Furthermore, the soil invertase, dehydrogenase, urease and acid phosphatase activities were all significantly higher than those in other fertilization treatments. There were significant correlations between soil microbial biomass, active organic carbon and the four soil enzymes activities, and these soil microbial properties were all positively correlated with soil pH, SOC, total N, total P, mineral N and available P except for the correlations between soil invertase, phosphatase and soil pH. So, manure application or co-application of manure and mineral fertilizers not only increased the quantity and quality of soil organic matter, but also enhanced significantly soil microbial biomass and soil enzymes activities, thus could improve red soil fertility and soil sustainable productivity.