Effects Of Conservation Tillage On Soil Enzymatic Activities In Dryland

On basis of the principal of soil biochemistry,a long-term located experiment was conducted to study the effects of different agricultural tillage practices on soil enzyme activities in the 0～5cm,5～10cm and 10～30cm depth in Soil Layers of the Loess Plateau.Based on effects of conventional tillage and five conservation tillage patterns'on soil enzymatic activities and grain yield in the rainfed farming system were studied.The examined tillage treatments were conventional tillage (T), conventional tillage with stubble incorporating (TS), no till with no stubble (NT), no till with stubble retention (NTS), conventional tillage with plastic mulching (TP) and no till with plastic mulching (NTP);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 2007.The items of measurement were soil catalase, urease, alkaline phosphatase and invertase activities.The results were the following.1 The effect of no-tillage on soil enzymatic activities:Treatments of no-till resulted in higher soil enzyme activities than the conventional tillage, which were not influenced by changes of season and cropping systems.2 The effect of straw cover on soil enzymatic activities: Treatments of straw cover resulted in which were no less than the treatments without straw cover of soil enzyme activities, which were not influenced by changes of season and cropping systems (not include TP).3 Changing tendency of soil enzyme activities under different rotation sequences:In the 0～30cm depth, for all treatments, the rotation of W accumulated soil catalase activities more than the rotation of P. In the 0～5cm depth, for T and TS treatments, the rotation of P accumulated soil urease activities more than the rotation of W, for NT and NTS treatments, however, the rotation of W accumulated soil urease activities more than the rotation of P. In the 5～10cm and 10～30cm depth, for T,NTS,NT and TS treatments the rotation of P accumulated soil urease activities more than the rotation of W. In the 0～30cm depth, for all treatments, the rotation of W accumulated soil alkaline phosphatase activities more than the rotation of P(not include in the 0～5cm depth, for NTP treatment). In the 0～30cm depth, for T,NT,TS,NTS and NTP treatments, the rotation of P accumulated soil invertase activities more than the rotation of W.4 Dynamics of soil enzyme activities under different agricultural growth season of dryland:With the spring wheat growth the enzyme activities of different treatments changed regularly and with the four enzyme activities had markedly changed trend for all treatments. In three soil depths, soil enzyme activities changes showed a similar trend for the same treatment. 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.5 The section scattergram distribution of soil enzyme activities in the soil depth under different agricultural measurements in dryland :The distributions of soil enzyme activities in different treatments were different. Before sowing section distribution of soil catalase activities among the T,NT,NTS and TS 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. The section distribution of soil hydrolytic activities including soil urease, alkaline phosphatase and invertase activities, in T, TS and TP treatments decreased from the soil profile of 0～5cm to 5～10cm and increased from 5～10cm to 10～30cm, while decreased in NT, NTS and NTP treatments from the soil surface to the deep soil layers which were not influenced by before sowing and after harvesting.