Effect Of Different Conservation Tillages On Soil Quality

The field experimental research was conducted in Dingxi Experiment Station Dry Land Farming of Gansu Agriculture University. The conservation tillage of the two rotation series (the rotation of spring wheat-field pea and the rotation of field pea-spring wheat) research has being studied for 6 years. The effects of conservation tillage on soil physical property, soil chemical property and soil biological property were researched, and the soil quality was evaluated, in the same time, established the system of quality evaluation. Four treatments were set in the experiment, which were conventional tillage with no straw (T), conventional tillage with straw incorporated (TS), no-till with no straw cover (NT) and no-till with straw cover (NTS). The main results obtained were summarized as follows:1. The effect of different conservation tillage methods on the soil physical property The soil aggregate was shown as that the contents of >0.25mm water-stable aggregate were improved under NTS,NT and TS comparing with T, and the aggregate structure was improved. In the vertical profile distribution of soil aggregate, the contents of >0.25mm water-stable aggregate under different tillage methods decreased with the increasing of soil depth.The soil micro-aggregate was shown as that the contents of >0.05mm soil micro-aggeate under NTS and NT were higher than TS and T, especially in the soil depth of 0-5cm. The no-tillage methods promoted the formation of big micro-aggregate and improved the soil structure.The MWD was shown as that the MWD under soil of NTS,NT and TS were bigger than T. In the vertical profile distribution of soil aggregate, the MWD diminished with the increasing of soil depth.2. The effect of different conservation tillage methods on the soil chemical property The soil organic matter (SOM) was shown as that the contents of soil organic matter under conservational tillage methods were higher than conventional tillage (T), and the promotion under NTS was best in the depth of 0-5cm. In the soil profile distribution of SOM, the contents of soil organic matter under different treatments decreased with the increasing of soil depth, but the decreasing amplitude was different, which were larger under NTS,TSand NT than that under T.The active soil organic carbon (ASOC) was shown as that NTS,NT and TS could promote the contents of ASOC comparing with T in the depth of 0-5cm, and the promotion was the most significant under NTS and TS. The results showed that the contribution of straw covered to the content of ASOC was more significant than the tillage methods. The contents of ASOC under NTS,NT,TS and T decreased with the increasing of soil depth. The decreasing amplitude was different, which were larger under NTS,NT and TS than that under T.The available nitrogen activity was shown as that the available nitrogen activity of tillage treatments were higher than that of no-tillage treatments in 0-30cm. The available nitrogen activity decreased at first, then increased with the increasing of soil depth.The available phosphorous activity was shown as that the available phosphorous activity was higher under conservational tillage methods in the soil surface (0-5cm). The available phosphorous activities under different treatments in the depths of 0-5cm and 5-10cm were higher than that in 10-30cm.The available potassium activity was shown as that the effect under tillage methods on the available potassium activity in the depth of 0-5cm was significant. In the soil profile distribution of available potassium activity, the available potassium activity decreased with the increasing of soil depth.3. The effect of different conservation tillage methods on the biological property The enzyme activities of the invertase, phosphatase, urease and catalase were shown as that NTS had the highest enzyme activity than NT and TS, and T was lowest in the depth of 0-5cm and 5-10cm. The enzyme activities decreased as the increase of the soil depth, especially under NTS.The solil microbial biomass carbon (MBC) was shown as that the contents of MBC under no-tillage treatments were higher than that under tillage treatments, especially in the depth of the 0-5cm, but the tendency decreased as the increasing of the soil depth. The contents of MBC decreased with the increasing of soil depth.4. Established the system soil quality evaluation and obtained the orders of soil quality index were NTS>TS>NT>T both in the spring wheat-field pea and in the field pea-spring wheat rotation sequences. The result showed that the function of keeping and improvement to soil under NTS was best than TS and NT, and T was the worst. From the angle of sustaining and improving the soil, NTS was the adaptable tillage method in the region.