| The vegetation cover and management factor C value are the effective indicators of evaluating the restraint of soil erosion impetus and appraising soil erosion modulus accurately. In this article we research on Soil erosion characteristics and Vegetation cover and management factor C value of sloping farmland in city of Chongqing, using observation data of mud which caused by nature rainfall flow in flowing section. The results are as follows:(1) The different duration of rainfall,rainfall intensity,slope length, slope of hilly area of purple slope have different of land runoff, sediment,sediment transport rate, slope denudation rate.In the continuous rainfall,runoff and erosion have obvious difference.Under the conditions of different initial water content of surface,runoff size and process are different.When duration of rainfall, slope length, slope and other conditions are same,the initial soil water content is relatively low, surface runoff is small. When the initial soil water content is high, surface runoff is large,two cases showed a certain linear relationship.(2) When the duration of rainfall,rainfall intensity and other conditions are same,the different slope has different amount sand of slope land as the rainfall.On the slope of15degree,4M length of slope area erosion far greater than2M slope length area of erosion, the former is about1.3times of the latter.Research shows,purple soil slope runoff is not as slope length increased linearly with increasing.The length of the slope increased erosion is increased in the presence of large fluctuation,but the length of the slope increases the general trend is the increased slope area of soil erosion.(3) Under different rainfall intensities, the hilly area of purple soil erosion of sloping cultivated land on the slope of the response characteristics of different.In the rain and strong conditions, when slope degree less than20, slope increased, production flow and runoff coefficient increases;when the slope is equal to20degree,production flow and runoff coefficient reaches a maximum, respectively0.97(L/m2/min),0.70; when slope degree more than20, slope increased, production flow and runoff coefficient decreases.In the heavy conditions, increasing slope, runoff coefficient of flow rate and a general trend of decreasing.When slope degree less than15,runoff coefficient rainfall increases; when slope degree more than20, runoff coefficient rainfall increases but decreases.Research shows that:the purple hilly land flow critical value is22.83degree,24.7degree sediment critical value.(4) The purple hilly land quantity,rate of sediment yield and runoff of rain intensity exists significant positive correlation with rainfall intensity, runoff coefficient between exist significantly negative correlation; the average rainfall intensity is reflected on purple soil slope land runoff amount,sediment rate best rainfall characteristic parameters.Research shows that:in the significance level P is equal to0.01,the average rainfall intensity and sediment,sediment yield and runoff coefficient between the correlation coefficient R is equal to0.9930,-0.9990and0.9913; I30can better reflect the characteristics of slope cropland of purple soil erosion, runoff, sediment and runoff coefficient of runoff sediment concentration, and the correlation coefficients were for0.9879*,0.9992**,-0.9923**and0.9778*.(5) In the same rainfall conditions in hilly areas of purple, of different cultivation mode of slope farmland soil and water conservation effects vary greatly,as follows: transverse slope of hedgerow farmland> cross slope farmland>slope farmland> clear fallow land.Cross slope of hedgerow cultivated annual average runoff (1266.7L) after clearing fallow ground,slope farmland respectively, cross slope farmland of1.21times,2.14times,but the average annual erosion amount (691.8g) is the smallest, only along the slope farmland, cross slope farmland of048times,0.71times,to "protect the role of soil water.".Sloping cultivated land surface layer vegetation coverage is the worst and rainfall erosivity more slots for soil erosion risk period, during the period take the corresponding protective measures can effectively control water and soil loss.(6) Based on the measured soil erosion amount of C value estimation method is the most suitable purple hilly land with different land use patterns in the C calculation; through the hilly area of purple main crops (wheat, sweet potato, wheat types/sweet potato) testing study on C value, C value of Wheat the purple hilly area is0.4345, sweet potato C value is0.3864, wheat and sweet potato year C is0.4037;C value of different show different crops on sloping farmland and protective effects of different value of C years,showed characteristic changes of crops on sloping farmland protective effect is as crop growth and development and gradually change, reasonable selection of crop species on soil and water conservation with obvious effect.(7)The purple hilly area slope farmland soil erosion prevention should improve the slope farmland vegetation coverage, optimize cultivate mode, both measures of soil and water conservation layout, realize the sustainable utilization of cultivated land slope.The rational construction of terrace slope ecosystem on the improvement of site conditions, reduce soil erosion, maintain agricultural ecological balance has significant benefit, soil and water conservation strategy based; and optimal use of terrace slope ecosystem is the realization of land productivity and economic benefits rise, for agricultural sustainable development in a new way, has broad prospects, to improve and protect the hilly area of purple soil erosion of sloping cultivated land, land degradation, plays a very important role. |
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