Evaluation of agricultural sediment load reductions using vegetative filter strips of cool season grasses

Vegetative filter strips for controlling. sediment generated from the bare ground (i.e., ground not protected by mulch or plant cover) were studied. P lots consisted of a 4.6-m clean-tilled upslope sediment source area and a 1 2.2-m vegetative filter strip located downslope from the sediment source ar ea. Vegetative filter strips consisted of pure stands of six adapted cool s eason grasses and two cereal grains. Sediment-laden runoff was transported into the upslope edge of each filter strip. Runoff samples were collected f rom the lower end of each plot and analyzed for nonflow weighted sediment c oncentration. The rate of advance of water through each vegetative filter s trip was measured. Additional measurements were made to define the plant ch aracteristics of each vegetative filter strip species. In general, planted vegetative filter strips resulted in a 68% reduction in concentration of se diment in initial runoff from a 50-year, 24-hour storm event on prewetted s oil. Crested wheatgrass and smooth bromegrass vegetative filter strips redu ced water flow velocity an average of 217% compared with the clean-tilled c ontrol plot. The length of time that water remained in the vegetative filte r strip modestly correlated with average sediment concentration in runoff t hat was 5.5 g/L and 5.0 g/L, respectively, compared with the control plot, which yielded 16.3 g of sediment/L of runoff. Under dry soil conditions, se diment concentration in runoff from bromegrass and crested wheatgrass was r educed by an average of 85% compared with the bare control plot. Length of time for water to advance through the smooth bromegrass and crested wheatgr ass vegetative filter strips increased an average of 325% compared with the length of time required to flow through the clean-tilled bare strip.