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 × 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 m 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 (NO3-N), 78% of the total-phosphorus (P), and 58% of the phosphate-phosphorus (PO4-P). The switchgrass/woody buffer removed 97% of the sediment, 94% of the total-N, 85% of the NO3-N, 91% of the total-P, and 80% of the PO4-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.
Footnotes
Kye-Han Lee, is post-doctorate research associate in the School of Forest Resource Conservation at the University of Florida, Milton, Florida. Thomas M. Isenhart, is associate scientist and adjunct assistant professor in the Department of Natural Resource Ecology and Management at Iowa State University, Ames, Iowa. Richard C. Schultz is professor in the Department of Natural Resource Ecology and Management at Iowa State University, Ames, Iowa.
- Copyright 2003 by the Soil and Water Conservation Society
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