Submitted to: Watershed Management Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: March 28, 2000
Publication Date: N/A
Technical Abstract: Inadvertent contamination of aquifers in Wellhead Protection Zones occurs, necessitating the installation of costly treatment systems. The public is better served by preventing contamination from the onset. One method is to regulate activities on the overlying landscapes. This is especially important in rural, agricultural settings where surface application of potential contaminants is common. The objective of this study was to identify crops and management systems that pose the greatest risk of nitrate contamination of drinking water supplies in agricultural areas that overlie shallow aquifers. Simulations were performed using the computer model GLEAMS (Groundwater Loading Effects of Agricultural Management Systems). The scenarios examined were: annual and perennial cropping systems; fine- and coarse-textured soils; high, low, and normal rainfall; irrigation with nitrate levels at low and high concentrations, and dryland. .The greatest amount of nitrates leached below the root zone under annual crops (corn, soybean) using current Best Management Practices (BMPs) and grown on sandy soils in normal to wet years. Growing perennial crops (alfalfa, bromegrass, orchardgrass) in wellhead protection zones resulted in a lower risk of nitrate leaching than growing annual crops, regardless of soil type or climate. A reduction of fertilizer inputs (75% of BMPs) to annual crops in these areas was marginally effective in limiting nitrate contamination, but with a subsequent reduction in yield. Public water supplies may be better protected if regulations or incentives were initiated to establish crop management systems in wellhead protection zones that promote perennial crops and/or limit fertilizer inputs on annual crops.