Evaluation of saturated buffer capacity to attenuate nitrate from agricultural land, Dakota County, MN

Since the 1950s, agricultural fertilizer use in the Midwest has expanded, leaching nitrate into the Mississippi River watershed and leading to the development of the hypoxic zone in the Gulf of Mexico. As a result, farmers and government officials in the Mississippi River\u27s sub-basins are interested in reducing agricultural nitrate runoff. One way to do this is by using a saturated buffer, a recently developed technology that filters water after it leaves croplands and before it enters surface and groundwater. This study examines the efficacy of a saturated buffer in Dakota County, Minnesota and compares it to an adjacent traditional riparian buffer. The goals of this study are to determine the saturated buffer\u27s ability to attenuate nitrate and to understand how pH, vegetation, and soil organic matter affect the saturated buffer\u27s ability to sequester nitrate, to provide nutrients to plants, and to facilitate denitrification. Weekly water sample collection throughout summer 2016 reveals that the Dakota County saturated buffer can attenuate nitrate. Soil samples show that the saturated buffer sequesters more nitrate than an adjacent traditional buffer. Soil organic matter and vegetation density suggest that denitrification and plant uptake occur in the saturated buffer. In both soil and water, higher average nitrate concentration is correlated to lower pH. Further research is needed on a variety of saturated buffer sites to understand fully the range of optimal environments for nitrate attenuation