Effects Of The Different Agricultural Tillage Methods On Soil Enzyme Activities In The Loess Plateau Dryland

On basis of the principal of soil biochemistry, an multi-year(6yrs) experiment was conducted to study the effects of different agricultural tillage practices on soil enzyme activities in the 0～5cm,5～10cm,10～30cm depth in loess soil of the Loess Plateau. The examined tillage treatments were T (Conventional cultivation and no straw),NT (No-till without straw),NTS (No-till with straw) and TS (Plough with straw incorporate).Basically, the experiment was designed with rotation. The rotation sequence was spring wheat (w) followed by field pea (p). Therefore, there are two phrases, spring wheat and field pea. Soil samples were collected in 2006.The items of measurement were soil urease , alkaline phosphatase, invertase and catalase activities. The results were the following.1 The effect of no-tillage:Treatments of no-till resulted in higher soil enzyme activities than the conventional tillages, which were not influenced by changes of season and cropping systems.2 The effect of straw cover:Treatments of straw cover resulted in higher soil enzyme activities than the treatments without straw cover, which were not influenced by changes of season and cropping systems.3 Dynamics of soil enzyme activities under different agricultural measurements:With the spring wheat growth the enzyme activities of different treatments changed regularly and had the same trend. Besides alkaline phosphatas activity in 10～30cm the fluctuations of the enzyme activities in the soil profile were similar. The activities of soil catalase and invertase increased previously, reached the maximum at the jointing stage, and then decreased during the filling and harvesting stage. The activities of soil urease and alkaline phosphatase increased previously, reached the maximum at the jointing stage, and then decreased gradually, finally increased during the filling and harvesting stage.4 The distribution of soil enzyme activities in the soil depth under different agricultural measurements: The distributions of soil enzyme activities in different treatments were different. The distribution of soil hydrolytic activities including soil urease,alkaline phosphatase and invertase activities in T and TS treatments reduced from the soil profile of 0～5cm to the soil profile of 5～10cm and increased from the soil profile of 5～10cm to the soil profile of 10～30cm, but reduced in NT and NTS treatments from the soil surface to the deep soil layers. Before sowing the distribution of soil catalase activities among the four treatments decreased previously ,reached the minimum at the depth of 5～10cm ,then increased from the soil profile of 5～10cm to the soil profile of 10～30cm.After harvesting soil catalase activities besides NT treatment all tended to decline with the soil depth.5 Changing tendency of soil enzyme activities under different rotation sequences:In the 0～5cm depth, for all treatments , the rotation of W accumulated soil alkaline phosphatase and catalase activities more than the rotation of P, however, the rotation of P accumulated soil invertase activities more than the rotation of P; Soil urease activities in the rotation of W were higher in the conventional tillage treatments and lower in the no-till treatments than those in the rotation of P. In the 5～10cm depth , for all treatments , the rotation of W accumulated soil urease ,alkaline phosphatase , invertase and catalase activities more than the rotation of P. In the 10～30cm depth , for all treatments , the rotation of W accumulated soil urease ,alkaline phosphatase and catalase activities more than the rotation of P; Soil invertase activities in the rotation of W were higher in the conventional tillage treatments and lower in the no-till treatments than those in the rotation of P.6 The correlation coefficient among the soil enzymatic activities reached significant level.