Relationships between soil properties and erodibility in Central Chile

Abstract

The soil erodibility is a measure of the susceptibility of soil particles to detachment and transport by rainfall and runoff. Texture is the principal factor affecting erodibility, but other soil properties such as structure, organic matter, and permeability also contribute. To investigate on the relationships between soil characteristics and local soil features, a study was carried out in the Central Valley of Chile, a geological depression between the Western Andes Mountains and the coastal range. Extending for about 1000 km (32°S to 40°S), the Central Valley consists of a vast thick deposit of heavily mineralized alluvial soils formed by the principal rivers of the region. A systematic topsoil analysis was performed to evaluate the relationships between soil erodibility and superficial physical and chemical properties. Soil erodibility was computed with two alternative methods based on 535 soil series identified from previously available soil surveys. The results show that erodibility decreased as the sand content in the soil increased. The opposite effect was observed for silt. When grouped by soil texture, all of the soils with less than 40% silt showed the same erodibility and were the least vulnerable to water erosion. On the other hand, the textures with the highest erodibility values were those where silt was the predominant particle size. In the study area, fine-textured soils showed higher levels of organic matter than coarse-textured soils, and this relationship between texture and organic matter content explained the absence of a direct correlation between organic matter and the erodibility factor. The results of this study demonstrate that soil erodibility is a complex property that is determined by a wide range of interlinked parameters.