Study Of Tillage Erosion And Its Effects On Loess Sloping Land

Tillage erosion is one of soil erosion processes, which may cause soil degradation and further severe soil and water loss on sloping cultivated land. These effects of tillage erosion are very obvious in the loess region of China where tillage history is very long. Research on tillage erosion has become a new area in the world recently, but little has been done in China. This paper, taking a typical sloping land in the loess region of hilly and gully in China as an example, quantitatively study tillage erosion and its effects there in the case of animal powered across-slope tillage operation by tillage erosion experiment in which small cubes are used as tracers of soil displacement, theoretical deduction, measurements, 137Cs tracing, repeated tillage, analyses of soil physics and chemistry, and statistics analyses. The research work has obtained innovational results which are significant in enhancing research on tillage erosion in the World and research on soil erosion in China, promoting efficient management of sloping land, controlling soil and water loss, and realizing sustainable use of soil resources in the loess region of China. The main progresses are as follows:1. Features of soil displacement in-processes of tillage are clarifiedStudy shows that the variations of horizontal and vertical soil displacements per tillage operation with slope gradient and depth can be described with a binary linear regression equation. The variations of soil depth after tillage with its depth before tillage and slope gradient can be described with a binary quadratic paraboloid regression equation. After per tillage operation, depth of soil with about one thirds of tillage depth did not change basically. Depth of soil shallower than one thirds of tillage depth became deeper than before. Depth of soil deeper than one thirds of tillage depth became shallower than before.2. Tillage erosion models for calculating soil flux and erosion intensity are developed Study shows that model for calculating tillage soil flux is a linear regression equationwhich describes relationship between soil flux per unit width per tillage operation at any position of sloping land and slope gradient. The model for calculating erosion intensity is that net soil erosion module (amount per unit area) per tillage operation at any position ofsloping land is equal to products of soil bulk density, tillage depth, coefficient determined with soil and tillage factors, and topography curvature.The tillage erosion models indicate that topography is the major factor affecting tillage erosion. It becomes a controlling factor when conditions of soil and tillage are fixed. The soil flux per unit width per tillage operation on sloping land is only related to slope gradient in a tillage process. The net erosion modulus per tillage operation on sloping land is only affected by topography curvature of the sloping land and is not correlated to slope gradient and slope length. A net erosion is mainly observed in the complex topography. When soil plough is implemented, net erosion is produced on convexities of slope profile and the deposition appears on concavities of slope profile. The more irregular and fluctuant the topography , the more extensive and intense the net erosion and deposition processes.3. Tillage erosion intensity and its spatial pattern are evaluatedStudy shows that soil flux per tillage operation is 24.02-44.58 kg-m'1 on study site. The segments of study site with soil flux less than 30.00 kg-m"1, between 30.00 and 40.00 kg-m' ', and grater than 40.00k kg-m"1 account for 23.43%, 42.07%, and 34.5% of the whole slope respectively, and mainly distribute in the upper and the lower parts, the upper middle and the lower middle parts, and the middle part of sloping land respectively.The tillage erosion modulus mainly ranges from 700 to 1800 t-km-2, taking an average of 1324.33 t-km-2 on study site. The net eroded area accounts for 49.24% of the slope, distributing on the convexity located in the upper part of the slope. The tillage depo...