Effects Of Long-term Fertilization On Soil Enzyme Activities Of Paddy Soil In Taihu Region

Taihu region is one of the centuries-old rice producing areas in China. Because of the biological character, high sensitivity and nice operability in analysis, soil enzymes have become an important fertility ixdex Of paddy soil. But there are few .literatures concerningβ-glucosidase and arylsulfatase activities of paddy soil in Taihu region, especially in long-term experiment. Wheat-Rice rotation, one of popular cultivation modes in China, is the coupling of two soil environments which are quite distinct from each other. But there is little report about systemic comparison of soil enzyme activities and the relationship between soil enzyme activities and soil fertility of Wheat-Rice system in long-term fertilization experiment. This paper chooses urease, acid phosphatase, alkaline phospatase,β-glucosidase and arylsutfatase activity as soil enzyme index to reaserch the soil enzyme activities and their relation to soil fertility of paddy soil under wheat-Rice system.of a 25a long-term fertilization experiment in Taihu region in 2006. Based on the characteristic of Wheat-Rice rotation, this paper analyse and compare the soil enzyme activities of two seasons individually and study the relationship between soil enzyme activities and soil fertility by Principal Component Analysis. And the effects of long-term rotation, season and fertilization to soil enzyme activities and the soil biochemical environment with dependable crop and high yield in different fertilizer of Wheat-Rice system are understood in order to offer scientific foundation and research thoughts. The main results are as follows:1 Effects of long-term fertilization on soil enzyme activities(1) Whether Chemical fertilizer or organic fertilizer is combined with chemical fertilizer, there is no obvious regularity among five types of soil enzyme activities variation in different fertilizer treatment of wheat system.(2) Whether Chemical fertilizer or organic fertilizer is combined with chemical fertilizer, there are no significant differences among most of soil enzyme activities in different fertilizer treatment of rice system. Namely, there are no significant effects of fertilization to soil enzyme activities of wheat system. The reason is that the soil fertilizer factors of rice system are not the effect and limited factors to a certain degree, and there are no material effects to soil biological activities by increase or decrease within limits.(3) Comparsion of paired-Samples shows that there are no significant differences among most of soil enzyme activities in same fertilizer treatment of wheat-Rice system beside NPK fertilizers combined with stable manure treatment, in which acid phosphatase activity of rice system is significantly higher than wheat system (P=0.001).2 Relationship among soil enzyme activities under long-term fertilizationA relative steady mutual stimulation mechnism exists between urease and arylsulfatase activity (r_0.05=-0.574) , alkaline phospatase andβ-glucosidase activity (r_0.05=-0.561) of wheat system, as well asβ-glucosidase and acid phosphatase activity (r_0.01=-0.743/r_0.01=-0.695) ,β-glucosidase and arylsulfatase activity (r_0.01=0.712/r_0.05=0.591) of paddy soil under wheat-Rice system by 25a long-term fertilization. Results show that there may be inter-relationships among between carbon and phosphorus cycle, carbon and sulphur cycle.3 Relationship between soil enzyme activities and soil fertilitie's factors under long-term fertilizationThere are differently significant line correlations between urease, acid phosphatase, alkaline phospatase,β-glucosidase, arylsulfatase activity and fertilitie's factor of wheat-Rice system, especially acid phosphatase andβ-glucosidase, which activities have significant line correlations with pH, available N, available P and organic matter. And there are significant line correlations between organic matter and the five types of soil enzyme activity. All the five types of soil enzyme activities have great propotion in the first and second principal component, which show that they have great contribution to soil fertility. It shows that acid phosphatase, alkaline phospatase,β-glucosidase and organic matter are the main facors in soil fertilirty. Soil enzyme activities can used to be important indexes to reflected s0il fertility, and soil fertility can be better evaluateed by phosphatase, arylsulfatase andβ-glucosidase activities than by urease activity. Soil enzyme activities can be used to evaluated soil fertility individually, or combined with soil fertilitie's factors. 4 Soil fertility evaluations under long-term fertilizationAccording to principal component comprehensive scores interzone, the four fertility grades are set off individually to order the 14 treatments of Wheat-Rice soil fertilizer systemⅠ(Soil enzyme activities and fertility factors of chemical fertilizer ) andⅡ(Soil enzyme activities and fertility factors of organic fertilizer combined with chemical fertilizer). The results from soil fertility evaluatirn in long-term fertilization experiment show that N combined with P fertilizer is the best cultivating mode, and soil fertility can be increased by appending phosphate fertilizer. The potassium resource is so immense in soil so that the effect of potassium fertilization in long-term fertilization experiment is very small. So there ia significant effect in N combined with P fertilizer based on this situation. No fertilization or only fertilization of organic fertilizer is both lead to degradation of soil fertility. The straw incorporation can improve soil fertility of wheat system, but has no obvious effect to soil fertility office system.