Long-Term Effects of Tillage and Crop Rotation on the Leaching of Nitrate and Pesticides to Shallow Groundwater

by R. S. Kanwar, Iowa State Univ, Ames, United States,
D. E. Stoltenberg, Iowa State Univ, Ames, United States,
R. Pfeiffer, Iowa State Univ, Ames, United States,
D. L. Karlen, Iowa State Univ, Ames, United States,
T. S. Colvin, Iowa State Univ, Ames, United States,
M. Honeyman, Iowa State Univ, Ames, United States,



Document Type: Proceeding Paper

Part of: Structures for Enhanced Safety and Physical Security

Abstract:

Contamination of groundwater by nitrate-nitrogen (NO₃-N) and pesticides is a serious problem and concern in Iowa. The extent of contamination can best be studied on plots with long term tillage and cropping histories. The objective of this study was to conduct field experiments to evaluate the effects of four tillage systems (moldboard plow, chisel plow, ridge tillage, and no-tillage) and two crop rotations (continuous corn and corn-soybean) on the leaching of NO₃-N and pesticides to shallow groundwater. Data for 1990 on the transport of atrazine, cyanazine, alachlor, metribuzin, and NO₃-N to shallow groundwater were analyzed. The average yearly NO₃-N losses with subsurface drainage water ranged from 30.3 to 107.2 Kg/ha. The no-tillage system under continuous corn increased infiltration, decreased NO₃-N concentration in groundwater, and increased total NO₃-N and herbicide losses to groundwater. Atrazine, alachlor, cyanazine, and metribuzin seem to move preferentially through macropores to groundwater after heavy rainfall events. More data on NO₃-N and pesticide leaching will be collected in the coming years which will help us in establishing cause-effect relationships.

Subject Headings: Pesticides | Crops | Groundwater pollution | Groundwater | Leaching | Water pollution | Agricultural wastes | Iowa | United States

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