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

item Watts, Dexter
item Torbert, Henry - Allen

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/9/2008
Publication Date: 7/1/2009
Citation: Watts, D.B., Torbert III, H.A. 2009. Impact of gypsum applied to buffer strips on reducing soluble P in surface water runoff. Journal of Environmental Quality. 38:1511-1517.

Interpretive Summary: Use of manure in agriculture can potentially cause negative impact to water quality, due to phosphorus (P) losses from the manure. Thus, a surface water runoff study was performed to evaluate the use of grass buffer strips and commercial gypsum added to grass buffer strips as a management practice to reduce P loss. A runoff event was evaluated directly after poultry litter application and four weeks after application. The runoff event directly after poultry litter application had the highest P loss compared to four weeks later. The use of a grass buffer strip was able to reduce some of the P loss, while the addition of gypsum to the grass buffer strip provided the best results. However, gypsum had lost its ability to reduce P loss in the surface water runoff event that occurred four weeks after poultry litter application. Thus, gypsum can be used to reduce P loss when applied before the initial surface water runoff event.

Technical Abstract: Environmental concerns resulting from the burgeoning poultry industry have sparked concern regarding water quality. These concerns are primarily a result of P transport from land application of manure, which threatens to accelerate eutrophication of surface water. Thus, a study was conducted to evaluate the effectiveness of a soil amendment 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 to supply 250 kg N ha-1 to the upper 3.05 m of each plot, while gypsum was applied at rates of 0, 1, 3.2, and 5.6 Mg ha-1to the lower 1.52 m of the plot functioning as a grass buffer strip. Two 30 min runoff events were conducted where surface water samples were collected at 10 min intervals and analyzed for soluble P. The first surface runoff event occurred immediately after PL application to evaluate the initial effects of the gypsum amendments; the second runoff event occurred four weeks later to evaluate the long-term effects. The greatest concentration of soluble P was observed in the runoff event that occurred immediately followed the PL application. Gypsum applied to grass buffer strips was effective in reducing soluble P concentrations at the highest rate in surface runoff, while the untreated buffer strip 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 the initial losses of soluble P from PL application when applied to grass buffer strip.