黄土高原水蚀风蚀交错带坡耕地土壤风蚀特征

Characteristics of Soil Wind Erosion on Sloping Farmland in the Water-Wind Erosion Crisscross Region on the Loess Plateau

黄土高原水蚀风蚀交错带受风力及水力共同作用,是世界上土壤侵蚀最严重区域之一。研究通过选取神木县六道沟流域迎风坡和背风坡4块坡耕地,所选样地进行留茬和翻耕处理,利用~7Be示踪技术测试表层土壤样品(0—20 mm),估算土壤风蚀速率,以期阐明坡面风蚀速率空间分布特征,明确有效防治风蚀的农田耕作措施。结果表明:迎风坡风蚀速率显著高于背风坡(p<0.05),留茬可显著减少坡面风蚀速率(p<0.05),迎风坡翻耕地、迎风坡留茬地、背风坡翻耕地和背风坡留茬地平均风蚀速率分别为778.2,388.4,78.5,4.7 t/(km^2·a)。风蚀速率沿坡面由上而下均呈现递减趋势,且留茬地更为显著。4块样地风蚀速率等值线的局部形变显示了坡面的微地貌变化,其中以留茬地更为明显且出现高侵蚀中心和沉积中心。因此,为有效防治该区域的土壤风蚀,建议采取秋收后留茬、春季播种前翻耕的方式,并根据坡向和作物类型等调整留茬高度。

The wind-water erosion crisscross region on the Loess Plateau is one of the most serious erosion areas in the world due to the combined action of wind and water. We selected four sloping farmlands facing opposite slope aspects in the Liudaogou watershed to study the effect of tillage pattern on soil wind erosion using ~7Be tracing approach. The selected fields remained crop stubbles or plowed after harvest. We collected surface soil samples(0—20 mm) from sloping farmlands with different management measures facing different slope aspects to estimate the rates of soil wind erosion, to delineate the spatial distribution characteristics of wind erosion rate, and to clarify effects of tillage measures on wind erosion. The results showed that wind erosion rate on windward slope was significantly greater than that on leeward slope(p<0.05);stubbleremaining could significantly reduce wind erosion in condition of applying the same tillage operations(p<0.05);wind erosion rates of farmlands of plowed land, and stubble land located on the windward slope and the leeward slope were 778.2 t/(km^2·a), 388.4 t/(km^2·a), 78.5 t/(km^2·a), and 4.7 t/(km^2·a), respectively;wind erosion rate decreased gradually in a top-down direction along the slope, and the reduction rates in the stubble fields were more significant than that in the plowed fields. The deformation of the wind erosion rate contours showed the changes of the micro-geomorphological, especially in the stubble plots with high erosion or deposition centers. Therefore, in order to effectively control soil wind erosion in the study region, we suggested to adopt the methods of stubble remaining after autumn harvest, plow before spring sowing, and increase stubble height according to slope aspect and crop types.