| Through the observation and analysis of soil and water loss and nutrient losses,this paper studied the effect and mechanism of different cutting-slope length & down-slope tillage measures under the same slope and different slopes to soil erosion. The same slope(10°)experiment was divided into 4 treatments, T1(CK)-straight tillage, T2-4m straight tillage&4m contour tillage, T3-5m straight tillage&3m contour tillage, T4-6m straight tillage&2m contour tillage.The different slope experiment was also divided into 4 treatments, S1-5°slope,7m straight tillage&2m contour tillage, S2-10°slope,6m straight tillage&3m contour tillage, S3-15°slope,4.5m straight tillage&4.5m contour tillage, S4-20°slope,3m straight tillage&3m contour tillage&3m traight tillage. The aim of the study was to provide theoretical basis for the further promotion of cutting-slope length & down-slope tillage measure in purple soil. The main conclusions are as follows:1.Comparing with the straight tillage, the runoff of cutting-slope length & down-slope tillage measure was decreased by 41.74%～59.63% and it can effectively reduce the runoff.In moderate rainfall condition,it showed its strong regulation function of runoff,but in heavy rainfall condition,it showed lower regulation function of runoff with the the increase of the slope length.2.1n Zhongxian the runoff of cutting-slope length & down-slope tillage measure was not relative to the rainfall or rainfall duration and the function of linear positive correlation of average raininess. On the same raininess condition, the responses of T1(straight tillag)to runoff was much higher than the one of cutting-slope length & down-slope tillage measure.At the same time, T2 was distinctly different from T3 and T4.But there was no significant differences between T3 and T4.In Suining the runoff of cutting-slope length & down-slope tillage measure was not relative to the average raininess or rainfall duration and present logarithm relevant to rainfall. 3. Comparing with the straight tillage, the cutting-slope length & down-slope tillage measure was remarkably effective in reducing soil erosion especially in strong rain condition. In moderate rainfall condition,there was no significant difference between the three cutting-slope length & down-slope tillage measures(T2,T3,T4).But in heavy rainfall condition, the increase of the slope length lead to reduced the soil conservation performance.4.The sediment loss of cutting-slope length & down-slope tillage measures under different slopes was not relative to the rainfall duration but the runoff(the significant correlation at the 0.01 level). The unit area sediment loss of S1(5°) was significant different from rainfall.And the unit area sediment loss of S2(10°),S3(15°),S4(20°) was significant different at 0.01 level from rainfall and runoff and significant different average raininess.5. Each measure in all previous rainfall, the runoff concentration of potassium was highest, nitrogen higher and phosphorus loss minimum.At the same time the available potassium concentration of runoff accounted for a high percentage of total potassium(58.16%～89.25%). The available N concentration account for total N came second, varying from22.85% to 89.25%. The available P concentration account for total P was lowest, varying from 6.40% to 22.67%. The unit area sediment loss of cutting-slope length & down-slope tillage measures was significant lower than the one of straight tillage.P:In common rainfall condition, T2 had best effect on reducing total phosphorus loss and there was no significant difference between T3 and T4. In heavy rainfall condition, the three cutting-slope length & down-slope tillage measures were significant different from each other.But available p concentration differences between them was not significant and the available p account for total phosphate was mainly effected by rainfall duration.N:In heavy rainfall condition, the runoff concentration of total N of each measure was low. In common rainfall condition, the cutting-slope length & down-slope tillage measure can effectively reduce the total N loss comparing with the straight tillage.And the three cutting-slope length & down-slope tillage measures was significant different from each other under short lasted rainfall condition but was not significant difference under long lasted rainfall condition. The available N account for total N was mainly effected by rainfall.K:The runoff concentration of potassium of each measure was high. Comparing with the straight tillage,T2 was remarkably effective in reducing potassium loss. There was no significant differences between T3 and T4. Rainfall had significant effects on total potassium and available potassium loss(at 0.01 level) but planting mode little effects because of the flowability of potassium.6.The sediment of each measure had a certain degree of soil nutrient enrichment and showed the the same enrichment trend, available K>available P>total P> organic matter> total N> available N> total K. All the nutrient enrichment ratio of T1 was higher than the one of other measures except organic matter, especially total P(1.45) and available P(1.90).The nutrient enrichment ratio of T2,T3 and T4 was not significantly different.7. Comparing with the straight tillage, the cutting-slope length & down-slope tillage measure can significantly reduce the sand content of slope position and increase silt and clay content by small degrees. Comparing with T3 and T4, T2 can significantly change the composition of surface soil particles.8. All cutting-slope length & down-slope tillage measures can not significantly keep surface soil potassium. S1 and S2 can effectively keep available P comparing with S3 and S4. As far as S1 and S2,the content of total N was lower at the top and upper position than the initial soil, and higher at the middle and lower slope than the initial soil. As far as S3and S4,,the content of total N was lower than the initial soil at entire slope. As far as S1,S2 and S3, the content of total P decreased at the top and upper position and increased at the middle position by a wide degree and increased at the lower and foot position by a small degree. Being different from S1,S2 and S3, the content of total P of S4 decreased at the top and lower position. The content of organic matter and available N of cutting-slope length & down-slope tillage measures didn't make much difference.
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