Effects Of Conservation Tillage On Soil And Water Conservation Under Artificial Rainfall

Because of the annual rainfall distribution was highly centralized and the soil was likelyto be eroded, soil erosion was extremely serious on the Loess Plateau, obstructing thesustainable development of dry-land agriculture. To analyze effects of conservation tillage onthe runoff volume、sediment production and processes of runoff and sediment could clear thebenefit and mechanism of conservation tillage. Article simulated rainfall experiments wereconducted to quantify the effects of straw mulching、stubble、tillage percentage and plantingdensity of corns on the runoff volume and sediment production and processes of runoff andsediment, so that to evaluate effects of conservation tillage on soil and water conservationcomprehensively, and to probe the mechanism of conservation tillage on reducing soil andwater loss.The results show that:1. Low straw mulching combined with high stubble shows clear effect, which is muchmore prominent when it’s on the dark loessial soils, on weakening the runoff, delaying theinitial runoff time by2.06times and reducing the runoff volume by20%in average. Strawmulching shows clear effect on weakening the soil erosion on different soils, reducing thesediment production both by93%when it’s on the Cultivated loessial soils and Lou soils andby91%when it’s on the Dark loessial soils.2. Effects on soil and water conservation is most obvious under low straw mulchingcombined with high stubble with corns planted, delaying the initial runoff time by91%inaverage and reducing separately the runoff volume and sediment production by21%and66%in average. Those effects are especially clear when it’s at the jointing stage of corns.3. The runoff volume of tillage with different percentage is increased compared withno-tillage when the rainfall intensity is90mm/h, increasing by6%in average when the tillagepercentage is30%and by35%in average when the tillage percentage is50%and by29%inaverage when the tillage percentage is70%and by14%in average when full-tillage. Whenthe rainfall intensity is120mm/h, the runoff volume of tillage with30%percentage isdecreased by3%in average, and of tillage with70%percentage is decreased by9%and3%separately with slope in5°and10°, however, the runoff volume is still increased by6%and11%separately when tillage with50%percentage and full-tillage. The difference betweentillage and no-tillage increases along with slope raised and decreases along with rainfall intensity declined. When the tillage percentage is50%, the runoff volume is the largest.4. The sediment production increases along with tillage percentage risen. When therainfall intensity is90mm/h, the sediment production is increased by1.37times in averagewhen the tillage percentage is30%and by2.83times in average when the tillage percentageis50%and by6.04times in average when the tillage percentage is70%and by7.36times inaverage when full-tillage. When the rainfall intensity is120mm/h, the sediment production isincreased by1.81times in average when the tillage percentage is30%and by3.54times inaverage when the tillage percentage is50%and by5.30times in average when the tillagepercentage is70%and by7.39times in average when full-tillage. Tillage with differentpercentage shows clear effect on soil erosion, the difference of sediment production betweentillage and no-tillage increases along with rainfall intensity raised when the tillage percentageis relatively small and decreases when the tillage percentage is relatively big.5. With the same tillage percentage and rainfall intensity, both the runoff volume andsediment production increases when the slope rises from5°to10°. The runoff volume withdifferent tillage percentage is increased by24%in average and the sediment production isincreased by5.7times in average when the rainfall intensity is90mm/h. The runoff volumewith different tillage percentage is increased by16%in average and the sediment productionis increased by4.83times in average when the rainfall intensity is120mm/h. When the sloperises from10°to15°, the sediment production is increased by85%in average when therainfall intensity is90mm/h and by1.19times when the rainfall intensity is120mm/h. Therunoff volume is decreased separately by8%and9%in average when no-tillage and thetillage percentage is30%, and both increased by11%in average when the tillage percentageis50%and70%, and there is no obvious change when full-tillage. Change of slope affects thesoil erosion obviously. The soil and water loss is much more serious with the slope raised.6. With the same tillage percentage and slope, the runoff volume and sedimentproduction is larger if the rainfall intensity increases. When the rainfall intensity rises from90mm/h to120mm/h, the runoff volume with certain tillage percentage under different slopeis increased by10%-40%in average, and the sediment production is increased by21%-63%.7. The planting density of corns could clearly affect the runoff and soil erosion underhigh stubble. When the planting density progressively increases from2600to5200trunks permu, the runoff volume is both decreased by7%in average, and the sediment production isdecreased separately by4%and15%in average at different growth stages. When the plantingdensity progressively increases from5200to7800trunks per mu, the runoff volume isincreased separately by9%and2%in average, but the situation of sediment productionshows a little difference. When the planting density is5200trunks per mu, the runoff volume and sediment production is least, conducing to the soil and water conservation most.8. When the growth stage advances from seeding stage to jointing stage, the runoffvolume and sediment production decreases separately by8%-20%and9%-42%.When thegrowth stage advances from jointing stage to heading stage, the runoff volume increases by11%-27%and the sediment production decreases by17%-34%. The change of growth stageinfluences the runoff volume most when the planting density is5200trunks per mu, andinfluences the sediment production most when the planting density is7800trunks per mu.