Efficiency of Grass Buffer Strips and Vegetation Height on Sediment Filtration in Laboratory Rainfall Simulations

Abstract

AbstractA laboratory rainfall simulation was conducted to compare the influence of three lengths of vegetation buffer strips and two vegetation heights on sediment filtration. The purpose of the experiment was to help evaluate stubble height grazing guidelines. Rainfall (50 mm h−1) was sprayed simultaneously over six trays (0.3 × 1.0 m). Concurrently, sediment laden (150 g tray−1) overland flow (50 mm h−1) was introduced to the upslope end of the trays. Two trays contained 12.5 cm, two trays contained 25.0 cm, and two trays contained 50.0 cm of Kentucky bluegrass (Poa pratensis L.) buffer strips during each simulation run. Paired buffer length trays either were clipped to the soil surface or grass was 10 cm tall. A significant interaction existed between vegetation buffer length and vegetation height. The clipped to the soil surface vegetation height was more effective as a sediment filter with the 12.5 cm buffer length than was the 10.0 cm height. Conversely, the 10.0 cm vegetation height was more efficient as a sediment filter with a 50 cm buffer length than was the clipped to the soil surface vegetation. No differences in sediment filtration efficiency existed between vegetation heights at the 25 cm buffer length. Additionally, 50 mm h−1 of rainfall was applied and 50 mm h−1 overland flow was added to six trays containing bare soil (no vegetation). Three the bare soil trays received sediment laden (150 g tray−1) overland flow and three trays received sediment free overland flow. All trays with the three vegetation buffer lengths had less sediment yield than did the bare soil trays. Results from this study suggest that vegetation height alone is not a suitable guideline for estimating sediment filtration and that length of vegetation buffer was more important than vegetation height in filtering sediment.