Soil erosion reduces the effective water available to plant

and loses the soil nutrient material with the soil fertility structure destroyed

effecting the farm tillage system. So

the soil productivity is cut down to a great extent. Erosion-Productivity Impact Calculators (EPIC) quantify the relationship systematically between soil erosion and soil productivity. The models involve 9 factors

that is

hydrology

meteorology

water erosion and wind erosion

the state of nitrogen and phosphorus

soil temperature

crop growth

tillage and treatment of crop residue

economic factors

and irrigation-drainage of soil as well as fertilization

etc. They are expressed with 36 equations. To protect and raise the soil productivity

we should develop and enhance this research in order to formulate EPIC with distinguishing Chinese feature.