Paper No. 350-5
Presentation Time: 9:00 AM-6:30 PM
EFFECTS OF PRECIPITATION ON NUTRIENT STORAGE IN A COVER CROPPED AGRICULTURAL WATERSHED
WATSON, Andrew L., Geography-Geology, Illinois State University, Normal, IL 61761, O'REILLY, Catherine M., Department of Geography and Geology, Illinois State University, Campus Box 4400, Normal, IL 61790-4400, PERRY, William L., City of Bloomington, 25515 Waterside Way, Hudson, IL 61748, HEATH, Victoria E., Department of Geography and Geology, Illinois State University, 101 S. School Street, Campus Box 4400, Normal, IL 61761 and BRUENING, Benjamin G., Minnesota Department of Agriculture, Rochester, MN 55901, alwats1@ilstu.edu
Nutrient runoff from agricultural practices in the Midwest is a significant contributor to degraded water quality in local watersheds and to the eutrophication of the Gulf of Mexico. This process is of increased concern in Illinois as much of the agricultural land is drained by subsurface tiles. Tile drains allow excess water in a field to drain quickly into a series of subsurface pipes which then deposit directly into neighboring creeks and streams. Tile drains hinder the soil’s ability to naturally filter out nutrients, leading to excess nutrient runoff in streams. Cover cropping is an upcoming practice that may help mitigate nutrient loss by utilizing non-cash crops to take up excess nutrients during the non-growing season.
This study analyzed how precipitation affected nutrient storage in a 1000-acre cover cropped agricultural watershed in Central Illinois. To do this, we installed an ISCO 6712 Portable Sampler in the field to collect water samples from a tile drain 24 inches in diameter. Daily rainfall data was collected using an FTS rain gauge and discharge data was recorded every 15 minutes by an ISCO 2150 Area Velocity Flow Module. Biweekly field data was manually collected from the tile drain using a YSI Professional Plus meter and a Flo-Mate Flowmeter. Nutrient levels were determined in the lab using a Flow Injection Analyzer.
Nitrate levels ranged from zero to 18.5 mg/L while daily rainfall ranged from zero to 71.2 mm. We observed a seasonal variation in discharge, with less response in discharge from rain events during the growing season. There was a linear increase in nitrate concentration with discharge.
The maximum contaminant level goal (MCLG) set by the EPA for nitrate in drinking water is 10 mg/L. The tile water we collected in this study frequently exceeded this value. A better understanding of how precipitation affects discharge and nutrient load will help us to reduce the nutrient footprint agriculture is leaving.
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