Red soil degradation has become a serious ecological and environmental problem due to irrational utilization.In recent years in particular,with intensive agricultural management targeting higher crop yields,overuse of chemical fertilizers has exacerbated the degradation of red soil.Organic amendment could not only reduce the dosage of chemical fertilizer used but also could improve overall soil quality,including soil physicochemical and microbiological properties that are relevant to soil ecosystem service maintenance and development.Soil enzyme activity is considered to be a valuable soil quality indicator with regard to its relevance to soil functioning and its sensitivity to soil perturbation.Numerous studies have investigated the impacts of fertilization management on soil enzyme activities,mainly focusing on the assessment of enzyme activity responses to different fertilizations however,little attention has been paid to additional information on ecophysiology and ecological stoichiometry associated with multiple enzymatic activities.In the present study,soil samples were collected from a long-term red soil fertilization experiment established in 1986 in the Jiangxi Institute of Red Soil of Jiangxi Province,and were analyzed to investigate the interactive effects of chemical and organic amendment on soil enzyme activity,soil physicochemical properties,and microbial biomass.In particular,the relationship among soil enzyme activity,soil physicochemical properties,and microbial biomass was explored.Four treatments,i.e.,no-fertilizer control (CK),only chemical fertilizer containing nitrogen,phosphorus,and potassium (NPK);only organic amendment (OM);and a combination of organic amendment and chemical fertilizer (NPKM),were selected for use in this study.The results showed that,compared with the CK,long-term fertilization practice (NPK,OM,and NPKM) could promote the activities of soil enzymes involved in carbon cycling (i.e.,α-and β-glucosidase,cellulase and xylanase) and nitrogen cycling (i.e.,leucine aminopeptidase and N-acetyl-β-d-glucosaminidase) to different extents.Among all the treatments,NPKM promoted overall enzyme activity the most,whereas NPK had the least affect.Organic amendment (i.e.,OM and NPKM) decreased the C:N acquisition ratio in comparison with CK,but there was no significant difference between NPK and CK treatments,indicating that organic amendment decreased the proportion of C-acquiring enzymes but increased N-acquiring enzymes.Microbial biomass carbon-specific enzyme activities (MBCE) or soil organic carbon-specific enzyme activities (SOCE) under the OM treatment was significantly lower than in the other three treatments.For example,compared to CK,MBCE was decreased by 56.2% and SOCE by 21.2% in the OM treatment,but these were increased by 7% and 16.9%,respectively,in the NPK treatment.Such results indicate that soil microorganisms obtained relatively more energy in the OM treatment and that the utilization efficiency of organic carbon was higher in this treatment than in the NPK treatment.Similarly,microbial biomass nitrogen-specific enzyme activities (MBNE) increased by 45% in the NPKM treatment compared to that in the CK,but no significant difference was observed between OM and NPK.The results suggest that low C:N acquisition ratio and high MBNE are indicators of N limitation in OM treatment,and organic amendment combined with chemical fertilization could alleviate N limitation.In conclusion,the soil microbial community is mainly limited by C in NPK,whereas it is mainly restricted by N in the OM treatment.Furthermore,NPKM treatment could simultaneously supply organic carbon and nitrogen,satisfying the demands of plant growth and producing a favorable environment for microbial growth.Integrating organic amendment and chemical fertilizer would facilitate sustainable development of soil ecosystem services.