A Colorado State University study indicates that riparian buffer strips are effective in filtering nutrients from runoff water entering streams, regardless of height and kind of vegetation. In this trial, plant communities made up of Kentucky bluegrass, tufted hairgrass, beaked sedge and water sedge removed about 84 percent of nitrogen and 79 percent of phosphorous from overland runoff, regardless of vegetation height.

Range scientists tested three plant heights-unclip-ped; clipped to about 4 inches and clippings removed; and clipped to the soil surface and clippings and litter removed. They used soil of known nutrient content to provide nutrient loading and a rotating boom rainfall simulator to create runoff. They collected the runoff in troughs at the lower end of each plot.

Results suggest that the presence of a vegetated buffer strip is more important to cleaning runoff water entering streams than the vegetation's characteristics. Thus, the scientists conclude, grazing management should aim to preserve streamside vegetation, but intensity of use is not so important to filtering ability.