DRYING INTERVAL EFFECTS ON RUNOFF - FROM FESCUE PLOTS RECEIVING SWINE MANURE

Application of swine (Sus scrofa domesticus) manure can lead to elevated runoff concentrations of organic matter and nutrients. This experiment was conducted to assess the influences of swine manure treatment (0 and 220 kg/ha nitrogen applied) and drying interval (4, 7, and 14 days) between manure application and first runoff event on quality of runoff from fescue (Festuca arundinacea Schreb.) plots. Runoff was generated from simulated rainfall (50 mm/h) and sampled at 0.08 h intervals during runoff Flow-weighted composite runoff samples from each treatment and replication were analyzed for nitrate nitrogen (NO3-N), ammonia nitrogen (NH3-N), total Kjeldahl nitrogen (TKN), total phosphorus (TP), chemical oxygen demand (COD), and total suspended solids (TSS). One set per treatment of the noncomposited runoff samples was also analyzed. Runoff concentrations of all manure constituents investigated were higher for the manure-treated plots than for the untreated plots. Runoff NO3-N increased with drying interval due to nitrification, but concentrations of other manure constituents were unaffected by drying interval. Amounts of constituents lost from the plots in runoff were higher for the manure-treated plots than for the untreated plots, but all (including NO3-N) losses were found independent of drying interval. Analyses of the noncomposited runoff samples revealed high variability in the response of runoff quality to time after the beginning of runoff for all parameters investigated Data from the noncomposited samples did not lend itself to generalized descriptions of changes with respect to time of runoff concentrations of manure constituents.