Effects of rainfall erosion factor, vegetation type and coverage on soil erosion of sloping farmland

Abstract: In order to discuss the effect of rainfall and vegetion on soil erosion of sloping farmland in cinnamon soil region in western Liaoning, the experiment was carried out under natural rainfall on artificial slope runoff plots from 2006 to 2010. The runoff plots with an interval of 1 m were designed according to the 20-year standard and each area was 60 m2. Slope factor was set as 5° and 10° respectively. Among 3 runoff plots built under the same slope, 2 plots were practiced by millet - sweet potato rotation, and another runoff plot was set as the control, which was the natural hillside field in 2006-2007 and bare slope (coverage <5%) in 2008-2010. Millet and sweet potato were planted as test crops by contour tillage and row spacing was 50 cm. The result showed that soil erosion in the sloping farmland mainly occurred between June and August, particularly in July. The surface runoff and erosion amount increased in accordance with the increasing of gradient and the effect of slope on erosion amount was greater than runoff with the slope increasing. When rainfall reached a certain intensity, soil erosion would occur. The experiment also showed that the surface runoff and erosion amount on sweet potato field had significantly positive relations with the rainfall (P<0.01 for runoff, P<0.05 for erosion amount), the maximum 30-minute rainfall intensity (P<0.01), the rainfall erosivity (which was the product of the former 2 factors) (P<0.01), and the product of rainfall and average rainfall intensity (P<0.01); the runoff on bare soil field had significantly positive relations with the rainfall (P<0.01 and P<0.05 on 5° and 10° bare soil field, respectively), and the rainfall erosivity (P<0.01); the erosion amount had significantly positive relations with the maximum 30-minute rainfall intensity (P<0.05 and P<0.01 on 5° and 10° bare soil field, respectively), and the rainfall erosivity (P<0.01), but had not positively significant relation with rainfall. The surface runoff and erosion amount were mostly affected by the precipitation and the maximum 30-minute rainfall intensity respectively through regression analysis and the both had not positively significant relation with average rainfall intensity on sweet potato and bare soil field. Erosion amount had a relation of power function and a significantly positive correlation with surface runoff under medium and higher rainfall intensity (P<0.01). The surface runoff and erosion amount on sweet potato field had a significantly negative exponential function relation (P<0.05). The amount of soil erosion on sweet potato field was the largest, the following was millet field and that of wild grass ground was the least. Multi variance regression analysis revealed that the factors impacting the amount of soil erosion from high to low were surface runoff, rainfall erosivity, and vegetation coverage, and the effects of rainfall erosivity and vegetation coverage on soil erosion increased with the slope increasing. Vegetation cover was especially important to protect against soil erosion on sloping farmland in western Liaoning, and crop management would be paid more attention with the increasing of gradient. The effects of different factors such as rainfall and crop varieties on soil erosion on sloping farmland were preliminarily known after the 5-year experiment in this paper. The research provides theoretical basis and technical support for the effective prevention and treatment of soil erosion in the region.