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Grazed pastures represent a potential source of non‐point pollution. In comparison to other nonpoint sources (e.g., row‐cropped lands), relatively little information exists regarding possible magnitudes of nutrient losses from grazed pasture, how those losses are affected by management variables, and how the losses can be minimized. The objective of this study was to measure concentrations of nitrogen (N), phosphorus (P), and solids in runoff from fescue plots and relate those measurements to simulated forage management strategy. The study was conducted at the University of Kentucky Maine Chance Agricultural Experiment Station north of Lexington. Plots (2.4 m wide by 6.1 m long) were constructed and established in Kentucky 31 fescue (Festuca arundinacea Schreb.) to represent pasture. The experimental treatments applied to the plots varied in terms of forage height and material applied (none, manure, or manure and urine). Runoff was sampled for six simulated rainfall events applied over the summer of 1997 and analyzed for nitrate N (NO3‐N), ammonia N (NH3‐N), total Kjeldahl N (TKN), ortho‐P (PO4‐P), total P (TP), and total suspended solids (TSS). All runoff constituents exhibited dependence on the date of simulated rainfall with generally higher concentrations measured when simulated rainfall followed relatively dry periods. The effects of forage height and manure addition were mixed. Highest runoff N concentrations were associated with the greatest forage heights, whereas highest P concentrations occurred for the least forage heights. Manure/urine addition increased runoff P concentrations relative to controls (no manure/urine) for both the greatest and least forage heights, but runoff N concentrations were increased only for the greatest forage heights. These findings indicate that runoff of N and P is at least as sensitive to amount and proximity of preceding rainfall and suggest that managing forage to stimulate growth and plant uptake can reduce runoff of N.

Pasture runoff can contribute to elevated concentrations of nutrients, solids, and bacteria in downstream waters. The objective of this study was to determine the effects of vegetative filter strip (VFS) length on concentrations and transport of nitrogen, phosphorus, solids and fecal coliform in runoff from plots treated with cattle manure. Three plots with dimensions of 2.4 × 30.5 m were used. The upper 12.2 m of each plot was treated with cattle manure, while the lower 18.3 m acted as a VFS. Runoff produced by rainfall simulators was sampled at VFS lengths of 0, 6.1, 12.2, and 18.3 m and analyzed for total Kjeldahl nitrogen (N), ammonia N, nitrate N, total phosphorus (P), ortho-P, fecal coliforms, total suspended solids and other parameters. The VFS significantly reduced concentrations and mass transport of incoming solids, fecal coliform, and most nutrient forms, particularly P. The relationships among VFS length, concentration and mass transport were well-represented by first-order exponential decay functions. Approximately 75% of incoming total Kjeldahl N, total P, ortho-P, and total suspended solids was removed within the first 6.1 m of the filter strips. Runoff concentrations of fecal coliform concentrations entering the filter strips were as high as 2 × 10 7 FC/100 mL; after a filter length of 6.1 m, however, the runoff exhibited no measurable concentration of fecal coliforms. This experiment suggests that even relatively short filter strips can markedly improve quality of runoff from grassed areas receiving cattle manure.

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