FECAL BACTERIA TRAPPING BY GRASS FILTER STRIPS DURING SIMULATED RAIN

Most fecal wastes produced by the poultry industry in Kentucky will be applied to agricultural land. Grass filter strips have been documente d to protect public waterways from soil erosion. We used a vain simula tor to investigate their potential to trap fecal bacteria in surface r unoff om poultry manure-amended cropland. We incorporated 165 Mg ha(-1 ) of poultry mature into each of four chisel-tilled plots and measured the trapping efficiency of 4.5 and 9.0 m grass filters for runoff sed iment and fecal indicator bacteria. Sediment concentrations were reduc ed an average of 96% by 4.5 m filter strips and 98% by 9.0 m filter st rips. Average fecal coliform trapping efficiency was 75% in 4.5 m filt er strips and 91% in 9.0 m filter strips. Average fecal streptococci t rapping efficiency was 68% in 4.5 m filter strips and 74% in 9.0 m fil ter strips. Flow-weighted fecal coliform concentrations in filter stri p runoff were still 1000 times higher than the standard for primary co ntact water wed in Kentucky (200 fecal coliforms per 100 mL). Grass fi lter strips long enough to minimize sediment loss will trap most of th e fecal bacteria in surface runoff but will not reduce fecal contamina tion of runoff to sufficiently meet existing water quality standard.