ABSTRACT
On-site impact of soil erosion is difficult to assess at local, regional, and global scales. The presently available information is based on a wide range of nonstandardized methods, incomplete and unreliable data, lack of information on the uneroded state of the soil and trends in erosion-induced changes in soil quality, and non-availability of precise cost of all losses (e.g., plant nutrients, water, soil organic matter content). Currently used methods of assessing the on-site impacts can be broadly grouped under three categories: agronomic/soil evaluation, economic assessment, and social surveys. Agronomic methods involve greenhouse and field experiments to relate erosion-induced changes in soil quality to agronomic productivity. Among these, a reliable technique is to establish field plots on soils with different severity of past erosion. Different erosional phases must be located on the same landscape position, and soil information on the uneroded reference soil must be available. Economic analyses of on-site impact involve assessment of losses of plant available nutrients and water and other additional inputs needed due to erosion. Knowledge surveys are based on “a structural informed opinion analysis” and are a qualitative substitute for locations where quantitative data are not available. These diverse approaches lead to a wide range of estimates of the on-site impacts. Consequently, the results obtained are not comparable and lead to conflicting views and debatable conclusions. There is a strong need to establish coordinated and long-term field experiments on principal soils and major ecoregions to evaluate effects of erosion-induced changes in soil quality and productivity. These experiments should be conducted with standardized methods, and scaling procedures should be developed to extrapolate the data from soilscape to regional and global scales.
