Erosion is a moving event or terangkutnya land or portions of land from one place to another by a natural medium (water or wind). Erosion can cause land degradation through loss or erosion of topsoil, so that could adversely affect the soil. The adverse effects of erosion seen from distinguished place so there are two, namely:
1. Impact on the scene erosion (on-site).
2. Impact outside the scene erosion (off-site).
The direct impact of erosion on-site include:
1. Loss of nutrients and organic matter.
2. The decline in infiltration capacity and the ability of soil to retain water.
3. Increased density and soil penetration resistance.
4. The stability and reduced soil structure which ultimately led to the deterioration of crop growth and declining productivity.
The indirect impact of erosion on site is reduced alternative to the use of land, the emergence of the urge to open up new land, the indirect impact outside the scene of erosion is loss due to a shortening of the lifetime of the dam, the increasing frequency and magnitude of floods (Arsyad, 2000). One of the environmental impacts arising from the development of agriculture through extending and intensifying – is the degradation of land or soil erosion. Pierce (1991) suggested that soil erosion affects soil productivity. Erosion can change the physical and chemical conditions of the soil.
Figure 2. Erosion
Each of different forms of land use will produce different levels of soil erosion as well. The erosion rate of the land affected by the type of vegetation that is planted and farming techniques used (Miranda, 1992).
Figure 3. Land bald
In Indonesia, the adverse effect of the process of soil erosion is not only experienced by agricultural land only, but also by forest area experienced residential areas, industrial areas are being built, the mining area, and so forth. In the area of agriculture alone, the process of erosion occurs on land managed slopes for cultivation of crops that are not equipped with soil conservation measures (Abdurachman and Sutono, 2002).