HR: 0800h
AN: H41C-0659    [Abstracts]
TI: Evaluating the Effectiveness of Native Grass Riparian Buffer Strips to Reduce Pesticide Runoff
AU: * Grossman, K
EM: kgrossman1@mail.csuchico.edu
AF: CSU, Chico, GEOS Dept. 400 West First St., Chico, CA 95929-0205, United States
AU: Brown, D L
EM: dlbrown@csuchico.edu
AF: CSU, Chico, GEOS Dept. 400 West First St., Chico, CA 95929-0205, United States
AB: Organophosphate pesticides such as diazinon have been a major source of non-point source water pollution in the Sacramento Valley watershed of central California. Diazinon is commonly listed as a pollutant for many tributaries of the Sacramento River on the US Clean Water Act section 303(d) list of impaired waterways. This pesticide is applied either aerially or as a foliar spray to nut and stone-fruit orchards during dormancy, which coincides with the rainy season in northern California. A study was conducted to determine if planting native grasses in the riparian zone was effective in reducing the amount of diazinon entering the surface water in streams flowing through these orchards. Native grasses have deeper root systems and were hypothesized to be more effective in sorbing diazinon and preventing its runoff than non-native grasses. In 2004, nine 20 foot by 20 foot riparian buffer plots were constructed along the banks of the South Fork of Walker Creek, west of the town of Orland in the Sacramento Valley. Three of the nine plots were maintained as bare ground, three were left with resident weeds including dense non-native grasses, and three were planted with native grasses, which included purple needlegrass (Nassella pulchra), creeping wildrye (Elymus triticoides), and deergrass (Muhlenbergia rigens). The experimental design simulated orchard runoff by applying mixtures of water and diazinon at observed field concentrations. The pesticide load was evenly applied across the top of each buffer plot at a rate consistent with local runoff rates in an average storm. Rainfall on the buffer plots was simulated with overhead sprinklers at a rate of 0.75 inches per hour, also an average storm for this area. Runoff was monitored at the downslope side of the plots with flumes funneled to large holding tanks. From these tanks, composite water samples were collected after runoff had ceased. The samples were analyzed for diazinon concentration, nitrates, and total suspended sediment. Results were similar to a demonstration and reconnaissance project conducted in 2003, which concluded that vegetative plots were more effective than the bare ground control in removing pesticide. However, the native grasses were not significantly more effective in reducing the diazinon concentration than non-native grasses. Vegetated buffer strips can help reduce pesticide loadings from orchards to local surface water systems.
DE: 1838 Infiltration
DE: 1871 Surface water quality
DE: 1895 Instruments and techniques: monitoring
SC: Hydrology [H]
MN: 2007 Fall Meeting