Submitted to: Journal of Environmental Quality
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/7/2004
Publication Date: 11/10/2004
Citation: Smith, D.R., Moore Jr, P.A., Miles, D.M., Haggard, B.E., Daniel, T.C. 2004. Decreasing phosphorous runoff losses from land applied poultry litter with dietary modifications and alum addition. Journal of Environmental Quality. 33:2210-2216. Interpretive Summary: Nutrients from animal manure that have been applied to fields as fertilizer contribute to the degradation of surface water. Phosphorus is the nutrient of greatest concern in fresh water systems, since it is the nutrient most limiting algae growth. Many methods have been developed to try to reduce phosphorus losses from animal manure applied to fields, including modifying the diet to reduce supplemental phosphorus inputs, and chemically treating the manure with chemicals to precipitate the phosphorus. In this study, poultry were fed commercial diets, or diets with high available phosphorus corn and/or phytase. Modified diets contained less supplemental phosphorus than the commercial diets. Aluminum sulfate was added to poultry litter between flocks of birds. After the third flock, litter was collected and applied to tall fescue plots. Rain was simulated on the plots at a rate of two inches per hour for 30 minutes and runoff from each plot was collected. Diet treatments reduced both total and soluble phosphorus in poultry litter, while alum treatment of litter did not affect the total phosphorus in litter, but did decrease the solubility of the phosphorus in manure. The highest levels of phosphorus in runoff water were from the plots fertilized with normal litter and not treated with alum. Diet treatments resulted in about a 45% reduction in phosphorus concentrations in runoff water, while a 60% reduction was noted for the alum treated litter. When diet modification and manure amendments were used together, reductions in runoff phosphorus concentrations were greater than when only one treatment was used by itself. This study has impact on the scientific community because it is the first study to show decreased phosphorus runoff resulting from dietary modification, and is also the first study to indicate that phosphorus losses can be reduced more effectively if diet and manure treatments are used together.
Technical Abstract: Phosphorus (P) losses from fertilization with animal manure has been implicated in the anthropogenic eutrophication of surface water. Producers can reduce potential losses of P from manure by using phytase or high available P (HAP) corn in diets, or by treating manure with chemicals, such as alum, to reduce P solubility. This study was conducted to compare the effects of dietary modification and manure amendments on P losses from poultry litter. Three flocks of poultry were fed a commercial diet, or diets modified with phytase and/or HAP corn. Litter was treated with alum at 10% by weight between flocks of birds. After the third flock, litter was collected and applied to plots cropped to tall fescue at a rate of 9 Mg/ha. Rainfall was simulated at 50 mm/hr until 30 minutes of continuous runoff was collected. Litter and runoff samples were analyzed for soluble and total P. Dietary modification reduced total P by as much as 39% and dissolved P by as much as 35%. Alum treatment of litter reduced litter dissolved P by 47%. Alum reduced P runoff by 60% compared to normal litter, while P runoff reductions were greatest when all three treatments were used together (69%). Alum treated litter resulted in greater forage yields, likely as a result of more N retained in litter prior to land application. The impact of this research is that it is the first study to show decreased P runoff from dietary modification, and also the first documentation of potential reductions to P losses in runoff when both dietary modification and manure amendments are used together.