Study On The Water Erosion Under 5 Years Conservation Tillage System In Loess Plateau

The effect of ground runoff, soil erosion, soil aggregation and soil organic matter under different years of conservation tillage system had been studied through the experiment of simulation rainfall in Dingxi as the typical semi-arid area of loess plateau. The results were summed up as below:1. The results showed that conservation tillage, which was characteristic with no-till with straw cover(NTS), could remarkably delay and reduce runoff and improve infiltration compared to other treatments.Under no-till with straw cover(NTS), the start runoff time was late, the runoff intensity was smallest and the capacity of soil and water conservation was the best . soil erosion was easily to take place under the traditional tillage(T).2. Under wheat→pea→wheat→pea→whea(tW→P→W→P→W)rotation sequence and wheat→pea→wheat→pea→wheat(W→P→W→P→W)rotation sequence, with the increase of soil depth in the layer 0～10cm, soil compaction under different treatments increased gradually. There was no regulation of soil compaction in the layer of 10~30cm under different treatments.From the soil moisture content, soil moisture contents both before and after rainfall under no-till with no straw cover(NT), no-till with straw cover(NTS) and conventional tillage with straw incorporated (TS) were higher than that under conventional tillage with no straw(T).And the Soil moisture contents with straw cover were higher than that with no straw cover. It was showed that, in the layer of 0~30cm, the soil compaction decreased are highly negative correlated with the soil moisture content.3. Under wheat→pea→wheat→pea→whea(tW→P→W→P→W)rotation sequence and wheat→pea→wheat→pea→wheat(W→P→W→P→W)rotation sequence, content of >0.25mm soil water-aggregates in the layer of 0~5cm was higher than that in the layers of 5~10cm and 10~30cm in all treatments. And the soil water-aggregates of 0.25mm～0.5mm and 0.5mm～1mm were the main particles in each treatments.4.The results showed that Under wheat→pea→wheat→pea→wheat ( W→P→W→P→W ) rotation sequence and wheat→pea→wheat→pea→wheat(W→P→W→P→W)rotation sequence, no-till with straw cover, conventional tillage with straw incorporated and no-till with no straw cover were advantageous to the developing of >0.25mm soil water-stable aggregates. It was also showed that, content of >0.25mm soil water-aggregates were increased with the increase of soil organic matter, >0.25mm soil water-stable aggregates are highly positive correlated with soil organic matter.5. Under wheat→pea→wheat→pea→whea(tW→P→W→P→W)rotation sequence and wheat→pea→wheat→pea→wheat(W→P→W→P→W)rotation sequence, in the layer of 0~30cm,﹥0.25mm stable percentage of aggregates with straw cover than that with no straw cover.And the soil erosion decreased with the increase of stability of >0.25mm soil water-aggregates.6. The results showed as following: under the rainfall intensity of 85mm/h,Under wheat→pea→wheat→pea→wheat(W→P→W→P→W)rotation sequence, runoff was alleviated and runoff intensity was reduced with NTS. Compared with NT,T and TS, runoff of NTS reduced 2.4%,34.7% and 12.1% respectively, infiltration increased 2.7%,38.6% and 13.6% respectively, runoff start time slowed down 1.17min,3.83min and 0.83min respectively, and quantity of soil erosion reduced 0.3%,62.4%and 17.7%respectively. Under wheat→pea→wheat→pea→wheat(W→P→W→P→W)rotation sequence ,runoff was alleviated and runoff intensity was reduced with NTS. Compared with NT,T and TS, runoff of NTS reduced 40.2%,18.4% and70% respectively, infiltration increased 44.9%,20.5% and 78.2% respectively, runoff start time slowed down 1.67min,2.16min and 1.38min respectively, and quantity of soil erosion reduced 119.8%,86.5%and 59.77% respectively.