SHADOWS ANALYSIS TO MEASURE SOIL SURFACE ROUGHNESS TO EVALUATE WIND EROSION
Authors: R. García Moreno, M.C. Díaz Álvarez, A.M. Tarquis and A. Saa Requejo
Abstract: Wind erosion can be evaluated from quantitative descriptions of soil surface roughness (SSR). Soil surface roughness describes the micro variation in the surface elevation across a field resulting mainly from tillage practices and soil texture. The study presented in this chapter, therefore aimed to fill the need for a reliable, low-cost, easy to carry and convenient method to measure that parameter. Based on the interpretation of micro-topographic shadows, this new procedure is primarily designed to use in the field The method has been named shadows analysis since the principle underlying the technique is the direct relationship between soil surface roughness and the shadows cast by soil structures under fixed sunlight conditions. The results obtained with this method were compared to the statistical indexes used to interpret field readings recorded by a pin meter. Three types of tillage tools (roller, chisel and tiller) were used to work two different soils (sandy clay loam and sandy loam), to obtain different SSR scenarios. The highly significant correlation between the statistical indexes and shadow analysis results obtained in the laboratory as well as in the field for all the soil-tool combinations proved that both variability (CV) and dispersion (SD) are accommodated by the new method. Also Multi Fractal Analyses were applied to the results of both methods to evaluate the influence on the resulting soil structure. This procedure simplifies the interpretation of soil surface roughness and shortens the time involved in field operations by a factor ranging from 12 to 20.