MADISON, WI, JULY 26, 2007- Excess nitrogen caused by fertilizers, animal waste, leaf litter, sewer lines, and highways is responsible for contaminating groundwater. It can also cause human health risks when found in drinking water and oxygen depleted water bodies endangering animals that drink from them. Establishing Riparian buffers is considered a best management practice (BMP) by State and Federal resource agencies for maintaining water quality, and they may be especially critical in controlling amounts of human produced nitrogen.
Scientists at the U.S. Environmental Protection Agency collected data on the buffers along with nitrogen concentration in streams and groundwater to identify trends between nitrogen removal and buffer width, water flow path and vegetation. They found wide buffers (>50 meters) removed more nitrogen than narrow buffers (0-25 meters). Buffers of different vegetation types were equally effective but herbaceous and forest vegetation were more effective when wider. Removal of nitrogen within the water was efficient, but not related with buffer width; however removal on the water surface was related to buffer width. Nitrate nitrogen (sometimes used in fertilizer) did not differ by width, flow path or vegetation type. Results from the study are published in the July-August 2007 issue of the Journal of Environmental Quality.
The study suggested that buffer width is important for managing nitrogen in watersheds. Other factors such as soil saturation, groundwater flow paths, and subsurface chemical/organism relations are important for governing nitrogen removal in buffers. Vegetation type also may be an important factor in certain landscapes and hydrologic settings where forested buffers may prevent nitrogen in deep groundwater or contribute more organic carbon in streams. Riparian buffers of herbaceous vegetation or a mix with forest vegetation were found to be effective only when wider.