ABSTRACT
Accelerated erosion driven by anthropogenic forces is the most widespread soil degradation process in the U.S. It is a physical process that results in permanent loss of effective rooting depth, and pollution of waters and emission of trace gases or greenhouse gases (GHGs) from soil. Whereas natural erosion is a constructive process that leads to formation of fertile soils around the world (river deltas, for example) and provides nutrients to water bodies for the growth of aquatic biota, accelerated erosion is a severe degradative process with adverse impact on productivity and the environment. Accelerated erosion is exacerbated by anthropogenic activities involving conversion of natural ecosystems to farmland. The extent, rate, and total magnitude of erosion are accentuated by deforestation, biomass burning, plowing and discing, cultivation of open-row crops, etc. Soil in unprotected tilled fields without any vegetal cover (Plate 5.1) may lead to the development of a surface seal and crust, high soil erodibility due to weak soil structure and low water infiltration rate (Plate 5.2), and concentrated flow (Plate 5.3) resulting in severe soil erosion. Among the principal land use classes (Chapter 3), cropland is the most susceptible to erosion by water because many farming practices remove the protective vegetative cover.
