VEGETATED FILTER STRIP REMOVAL OF CATTLE MANURE CONSTITUENTS IN RUNOFF

Pasture runoff can contribute to elevated concentrations of nutrients, solids, and bacteria in downstream waters. The objective of this stud y was to determine the effects of vegetative filter strip (VFS) length on concentrations and transport of nitrogen, phosphorus, solids and f ecal coliform in runoff from plots treated with cattle manure. Three p lots with dimensions of 2.4 x 30.5 m were used. The upper 12.2 m of ea ch plot,vas treated with cattle manure, while the lower 18.3 m acted a s a VFS. Runoff produced by rainfall simulators was sampled at VFS len gths of 0, 6.1, 12.2, and 28.3 m and analyzed for total Kjeldahl nitro gen (N), ammonia N, nitrate N, total phosphorus (P), ortho-P, fecal co liforms, total suspended solids and other parameters. The VFS signific antly reduced concentrations and mass transport of incoming solids, fe cal coliform, and most nutrient forms, particularly P. The relationshi ps among VFS length, concentration and mass transport were well-repres ented by first-order exponential decay functions. Approximately 75% of incoming total Kjedahl N, total P, ortho-P, and total suspended solid s was removed within the first 6.1 m of the filter strips. Runoff conc entrations of fecal coliform concentrations entering the filter strips were as high as 2 x 10(7) FC/100 mL; after a filter length of 6.1 m, however the runoff exhibited no measurable concentration of fecal coli forms. This experiment suggests that even relatively short filter stri ps cam markedly improve qualify of runoff from grassed areas receiving cattle manure.