Effectiveness of vegetative buffers on sediment trapping in cultivated areas

Abstract

Vegetative buffers have been investigated and proposed as a means of reducing sediment and nutrient loadings in streams by minimizing cropland runoff. Buffers may increase infiltration, slow runoff, and allow more time for sediment to deposit. Unlike most of the previous research where buffer effectiveness has been measured using simulated runoff events on small plots, the main objective of this study was to collect buffer data in actual fields. With this in mind, two sites at different locations in Wisconsin were selected. The sites provided different field sizes and shapes, slopes, soil textures, and agricultural practices. Site 1 had a 0.03-ha contributing area with slopes varied from 0.5 to 9.0% (5% average slope). The field was planted first with corn and later with soybean. Row direction was up and down slope, and the soil is a clay loam. A downstream adjacent area was planted with grass as a vegetative buffer. Site 2 had a 0.10-ha contributing area with a 10% average slope, as was planted with corn during the first year and alfalfa later. Row direction was across the slope, and the soil is a sandy loam. This site also had a downstream adjacent area planted with grass as a buffer. At each site the rainfall rate was recorded, and runoff and sediment were collected before and after the buffer with using a multislot divisor system specially designed for this purpose. The runoff and sediment collectors were operative during three years, and collected runoff from both rainfall and snowmelt. This paper presents an overview and evaluation of this long-term study.