Content area
Full Text
ABSTRACT: Riparian buffers are widely recommended as a tool for removing nonpoint source pollutants from agricultural areas especially those carried by surface runoff. A field plot study was conducted to determine the effectiveness of an established multi-species buffer in trapping sediment, nitrogen, and phosphorus from cropland runoff during natural rainfall events. Triplicate plots were installed in a previously established buffer with a 4.1 by 22.1 m (14 x 73 ft.) cropland source area paired with either no buffer, a 7.1 m (23 ft) switchgrass (Panicum virgatum L. cv, Cave-n-Rock) buffer, or a 16.3 m (53.5 ft) switchgrass/woody buffer (7.1 rn swithgrass/9.2 m woody) located at the lower end of each plot. The switchgrass buffer removed 95% of the sediment, 80% of the total-nitrogen (N), 62% of the nitrate-nitrogen (NO^sub 3^-N), 78% of the totalphosphorus (P), and 58% of the phosphate-phosphorus (P0-P). The switchgrass/woody buffer removed 97% of the sediment, 94% of the total-N, 85% of the NO^sub 3^-N, 91% of the total-P, and 80% of the PO^sub 4^-P in the runoff. There was a significant negative correlation between the trapping effectiveness of the buffers and the intensity and total rainfall of individual storms. While the 7 m (23 ft) switchgrass buffer was effective in removing sediment and sediment-bound nutrients, the added width of the 16.3 m (53.5 ft) switchgrass/woody buffer increased the removal efficiency of soluble nutrients by over 20%. Similar or even greater reductions might have been found if the 16.3 m (53.5 ft) buffer had been planted completely to native warm-season grasses. In this buffer, combinations of the dense, stiff, native warm-season grass and woody vegetation improved the removal effectiveness for the nonpoint source pollutants from agricultural areas.
Keywords: Erosion, grass filter, nonpoint source pollution, riparian buffers, water quality
Nonpoint source (NPS) pollution is one of the most critical problems threatening the nation's water resources, and agriculture accounts for up to two-thirds of this pollution (Long, 1991). Accordingly, various types of best management practices (BMP's) have been developed to reduce the movement of pollutants from agricultural areas. Whereas on-site BMPs reduce pollutant transport from agricultural sources in many cases, they are not adequate to meet national water quality goals in other situations (Clausen and Means, 1989).
Riparian buffers are being used...