Soil erosion is a widespread and major environmental threat to our
terrestrial ecosystems (Singer and Warkentin, 1996; Yang et al., 2003).
During the last 40 years, nearly one-third of the world's arable land
has been lost to erosion, with loss continuing at the rate of more than
10 million ha per year (Pimental et al., 1995). Soil erosion is directly
related to reduced agricultural productivity and to water pollution,
and it may reduce the ability of soil to mitigate the greenhouse effect
(Lal and Bruce, 1999; Nearing et al., 2005; Weltzin et al., 2003). Soil
erosion by water is considered one of the most severe types of erosion
and has attracted considerable attention in the past, mainly due to its
destructive effects, including eutrophication, non-point pollution and,
eventually, land degradation (Asselman et al., 2003; Jin et al., 2008;
Singer and Shainberg, 2004).