EFFICIENCY OF GRASS BUFFER STRIPS AND VEGETATION HEIGHT ON SEDIMENT FILTRATION IN LABORATORY RAINFALL SIMULATIONS

A laboratory rainfall simulation was conducted to compare the influenc e of three lengths of vegetation buffer strips and two vegetation heig hts 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 x 1.0 m), Concurrently, se diment laden (150 g tray(-1)) overland Bow (50 mm h(-1)) was introduce d to the upslope end of the trays. Two trays contained 12.5 cm, two tr ays contained 25.0 cm, and two trays contained 50.0 cm of Kentucky blu egrass (Pea pratensis L.) buffer strips during each simulation run, Pa ired buffer length trays either were clipped to the soil surface or gr ass was 10 cm tall. A significant interaction existed between vegetati on buffer length and vegetation height, The clipped to the soil surfac e vegetation height was more effective as a sediment filter with the 1 2.5 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 5 0 cm buffer length than was the clipped to the soil surface vegetation , No differences in sediment filtration efficiency existed between veg etation heights at the 25 cm buffer length. Additionally, 50 mm h(-1) of rainfall was applied and 50 mm h(-1) overland Bow was added to six trays containing bare soil (no vegetation), Three of the bare soil tra ys received sediment laden (150 g tray(-1)) overland Bow and three tra ys received sediment free overland flow. All trays with the three vege tation buffer lengths had less sediment yield than did the hare soil t rays, Results from this study suggest that vegetation height alone is not a suitable guideline for estimating sediment filtration and that l ength of vegetation buffer was more important than vegetation height i n filtering sediment.