ABSTRACT
Soil and water are the most valuable natural resources to meet the basic needs of food, feed, and fiber for human beings. However, conserving soil and water resources is a growing challenge as they are under increasing stress to produce more food for the ever growing population. The loss of soil surface layer, which contains most nutrients and organic matter, reduces fertility. In addition, high runoff water causes moisture stress in the later part of the season, leading to low and variable crop productivity especially under rainfed conditions. Globally, total area affected by moderate to serious soil erosion is estimated around 1028 million ha, of which 748 million ha is due to water erosion and the rest by wind erosion. In Asia and Africa, 673 million ha area is impacted by erosion (Oldeman et al., 1991). It is estimated that 186 million ha area is affected by chemical and physical degradation, which reduce vegetative cover and exacerbate soil erosion (Oldeman et al., 1991). In Asia, South America, and Africa soil erosion rates are the highest with estimated average of 30-40 t ha−1 yr−1, while in Europe and North America average rates are somewhat lower at about 17 t ha−1 yr−1. A sustainable rate of soil loss (rate of soil loss is equal to rate of soil formation) is thought to be about 1 t ha−1 yr−1 (Pimental et al., 1995).
