Nitrogen Losses from Agricultural Landscapes: A perspective from the stream

A novel sampling platform based on a light-weight kayak equipped with high-frequency sensors, an automated discrete sampling system, and a GPS unit has been developed to take spatially resolved measurements of nitrate concentrations and other water quality parameters in small headwater streams. The continuous, spatially explicit water quality data gathered with this sampling platform can be coupled with high-resolution land use information and DEM-derived stream networks to approximate individual sub-catchments’ contributions to total watershed nitrogen export.

Beginning in 2021, this sampling strategy was employed in an agriculturally dominated watershed within the Minnesota River Basin to characterize nitrogen export behavior at the sub catchment scale. Post-settlement, this watershed was extensively hydromodified by subsurface tile installation and stream channelization to support agricultural production. Coupled with increased nitrogen fertilization, these characteristics make this landscape a large contributor to
downstream nitrogen export. Event based sampling across multiple seasons using this sampling methodology enables us to better understand how the timing and magnitude of precipitation events influences nitrogen loss at specific watershed locations that contain distinct soil types, landscape features, and agricultural practices. These efforts will improve our understanding of
nitrogen dynamics in agricultural land by bridging the spatial gap between field and watershed scale observations of nitrogen export behavior. With this increased understanding, conservation practices aimed at decreasing nitrogen loss can be targeted where they will be most effective.