UC ANR Sierra Foothill Research & Extension CenterInvestigator
Kenneth Tate, Ph.D.
University of California, Davis
During 2004-2007 we made significant progress on the completion of this project's founding objectives. We completed 2 of the 3 experiments proposed in 2004, and have completed ~30% of the 3rd proposed experiment. Completed experiments examined: 1) the efficacy of 2 small wetlands at SFREC to attenuate microbial, sediment, and nutrient pollutants in runoff from irrigated pastures under various rates of tailwater discharge; and 2) the impact of stocking rate, irrigation water application rate, and timing of grazing relative to irrigation on the transport of E. coli from 10 irrigated pastures. Results of the two completed studies have been accepted with minor revision in California Agriculture, and are under review in the J. Environmental Quality. Wetlands filtered from 40 to 90% of pollutants contrinuted to them with filtration efficiency decreasing as tailwater discharge rate increased and hydrologic residence time decreased. We also found that E. coli levels in tailwater increased as irrigation water application rate increased, stocking rate increased, and days rest between grazing and irrigation decreased. These results indicate that integrated pasture management best management practices and implementation of wetland filters can effectively reduce pollutant levels in pasture dishcarge. We will complete the remainder of the 3rd experiment during the next review period, which focuses on the efficacy of linear vegetative buffer strips to filter pathogens and organic C from pasture runoff.