Effects of agricultural activities on water pollution with nitrates and pesticides in the Central Valley of Chile

The objectives of this study are, first, to describe the present use of fer tilisers between the Regions III and wr of Chile, identifying the associate d environmental impacts and their relationship with the predominant agricul tural practices and climatic characteristics. Secondly, to simulate the tra nsport of nitrates and pesticides in a dairy and breeding farm of the Centr al Valley of Chile, employing EPIC (USDA/ARS) in order to determine the imp ortance of these contamination processes. In the North area of Chile, agric ultural production generates soil and groundwater salinization problems due to low average rainfall and the use of highly efficient irrigation practic es. In the Central zone, nitrate contamination due to agricultural diffuse pollution is evident; this is especially valid for groundwater contaminatio n with nitrates. The South Central area suffers from eutrophication due to an increase in the nutrient levels in surface water. The simulation indicat es that the dairy farm in the Central Valley of Chile has a soil loss of 5. 02 tons/ha/year or of 14.67 tons/ha/year, based on MUSS or USLE estimates, respectively. It is important to point out that loss of NO3 and pesticides estimated by MUSS and USLE do not exceed maximum allowable standards. (C) 1 999 IAWQ Published by Elsevier Science Ltd. All rights reserved.