Impact of Gypsum Applied to Buffer Strips on Reducing Soluble P in Surface Water Runoff.

Concerns for environmental quality from the burgeoning poultry industry have prompted concerns in recent years.  These concerns are primarily a result of P transport from land application of manure, which poses a threat to accelerated eutrophication of surface water. Thus, a study was conducted to evaluate the effectiveness of soil amendments applied to grass buffer strips in reducing soluble P in surface runoff. A simulated concentrated flow study was conducted in an established tall fescue pasture. Poultry litter (PL) was applied at a rate of 250 kg N ha^-1 to each plot. Soil amendments were then applied to the grass buffer strips at rates of 0, 1, 3.2, and 5.6 Mg ha^-1. Two 30 min runoff events were conducted, in which, surface water samples were collected at 10 min intervals and analyzed for soluble P.   The first surface runoff event occurred directly after PL application to evaluate the initial effects of soil amendments and the second runoff event occurred four weeks later to evaluate the long-term effects of soil amendments. The greatest concentration of soluble P was observed in the runoff event that occurred directly after PL application. The highest rate of gypsum applied to grass buffer strips were very effective in reducing soluble P concentrations in surface runoff, while the buffer strip itself was somewhat effective. In the second runoff event, although the concentration of soluble P was greatly reduced, the effect of gypsum had diminished. These results show that gypsum is most effective in reducing of initial losses of soluble P from PL application when applied to grass buffer strip.