Enzyme Activities and Soil Nutrition Status as Affected by a Long-term Located Fertilization in a Loessial Soil

Based on 25 years of fertilization experiment,the effects of different fertilizer treatments on the contents of the soil labile organic matter(LOM),nitrogen(N) and phosphorus(P) nutrients,and soil enzyme activities were investigated in this study.The results showed that the contents of LOM,total N,available N and available P increased significantly after long-term fertilization,and the activity of soil invertase and phosphatase increased simultaneously.Furthermore,the combined application of organic and inorganic fertilizers influenced much more on soil nutrient and soil enzyme activities than inorganic fertilizers applied only.However,the soil catalase activity was not increased in our study site.Correlation analysis indicated that the activities of soil urease,invertase and phosphatase were positively correlated with the contents of LOM,total N,total P,available N,and available P.Furthermore,the activities of these three enzymes correlated significantly with each other.Consequently,the results showed that the soil enzyme activities could be used as the biological index in the study of soil fertility and quality,and it was valuable for improvement of soil fertility in this area.