UNDERSTANDING THE AMOUNT OF NITRATE IN RELATION TO PERCENT OF ORGANIC MATTER IN RIPARIAN BUFFER ZONE SOILS AT STREAM T3 IN HUDSON, ILLINOIS

A major threat to water quality in the agricultural Midwest is the amount of nitrate that comes directly from fertilizer used in agricultural fields. In order to better understand how nitrate affects streams and their riparian buffer zones, we have been conducting research at the stream T3, which is located in Hudson, Illinois. This stream flows into Lake Evergreen, one of the drinking water reservoirs for Bloomington-Normal, IL. There is growing concern for the quality of the drinking water as a result of elevated nitrate in the contributing stream. We collected soil samples for 10 nested wells that were installed in various places and depths in the riparian buffer zone to measure nitrate concentrations and percent of organic matter. The soil samples were frozen and then dried at 100°C for at least 24 hours. Samples were mixed with KCl, shook, and then filtered, so they could be analyzed for nitrate concentration in the Ion Chromatograph. Soil percent organic matter was measured by drying a known mass of sample at 540°C for 24 hours. The concentration of nitrate in the soil water ranged from below detection limits to 26.55 mg/L. Nitrate concentrations decrease with depth with an average of 16.26 mg/L at a depth of 1 foot and 7.14 mg/L at a depth of 6 feet. The soil contained a relatively high percent organic matter ranging from 10.94% near the surface to 1.51% at a depth of 6 feet; however, there was no correlation between amount of nitrate and percent of organic matter. The concentrations of organic matter and nitrate suggest that the riparian buffer zone has the capacity to reduce nitrate, and if tile-drained water were diverted into the soil of the riparian buffer zone, denitrification and/or uptake of nitrogen from plants would occur.