Effects of Perennial Grass Buffer Strips on Movement of NPS Pollutants from Cropland to Wetland

Previous research has shown that vegetative buffer strips are effective at protecting water quality. Most of the research has been conducted on the east coast. Our research goals are to determine whether native perennial grasses serve to restore native biodiversity while simultaneously capturing both sediment and nutrients from adjacent conventional row-cropped agriculture. In particular, we are evaluating the efficacy of buffer strips in Mediterranean climate. Buffer strips bordering Elkhorn Slough, draining into the Monterey Bay National Marine Sanctuary, have received one of three treatments: annual non-native grasses, perennial native grasses, and an unseeded treatment of weedy volunteers. We measured sediment movement as part of an erosion study and quantifying nitrogen and phosphorus pools in soil, surface water, soil water, groundwater and vegetation. In addition, we have looked at the mechanisms and processes involved in nitrogen transformation to understand the fate of the nitrogen. Preliminary results from the erosion study indicate that the annual treatment was most effective in preventing erosion in the first year, whereas the perennial grasses were more effective in the second and third years. Results from the groundwater study indicate a significant decrease in nitrogen concentration with an increase in buffer strip length. Hydrologic tests are being analyzed to understand the pathways and dilution interactions. Nitrogen dynamics suggest that gaseous loss is an important pathway for the loss of nitrogen from the field. The relative contribution of trace gasses to the atmosphere needs further investigation