Vegetative Filter Strips for Agricultural Nonpoint Source Pollution Control

ABSTRACT Arainfall simulator was used to evaluate the effective-ness of vegetative filter strips (VFS) for the removal of sediment, nitrogen (N), and phosphorus (P) from cropland runoff. Simulated rainfall was applied to nine experimental field plots on an eroded Groseclose silt loam soil (clayey, mixed, mesic Typic Hapludalt) with a 5.5 by 18.3 m bare cropland source area and either a 0, 4.6, or 9.1 m VFS located at the lower end of each plot. Fertilizers were applied to the plots at rates of 222 kg/ha of liquid N and 112 kg/ha of P2O5 and K2O. Water samples were collected from the base of each plot and analyzed for sediment and nutrient content. One set of plots was constructed to encourage concentrated rather than shallow uniform flow. The 9.1 and 4.6 m VFS with shallow uniform flow removed an average of 84 and 70% of the incoming suspended solids, 79 and 61% of the incoming P, and 73 and 54% of the incoming N, respectively. Soluble nutrients in the filter effluent were sometimes greater than the incoming soluble nutrient load, presumably due to lower removal efficiencies for soluble nutrients and the release of nutrients previously trapped in the filters. Concentrations of soluble inorganic N and P in filter strip effluent were sufficient to cause eutrophic plant growth in aquatic ecosystems. Observation of existing VFS showed that on-farm VFS were not likely to be as effective as experimental VFS because of problems with flow concentrations.