Arkansas Agricultural Experiment Station, University of Arkansas Division of Agriculture
Dale Bumpers College of Agricultural, Food and Life Sciences
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Table of Contents • Notable • Cochran named Associate Vice President for Agriculture-Research Vision Credits
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Alum curbs phosphorus in poultry litter, provides other benefitsResults from the first 10 years of two 20-year studies by adjunct professor Dr. Philip Moore, show that poultry litter doesn't have to be a significant pollution source if proper application guidelines are followed, according to a report in the latest issue of Agricultural Research, a USDA publication.
Moore is a USDA Agricultural Research Service scientist in the Poultry Production and Product Safety Research Unit and an adjunct professor in the Department of Crop, Soil, and Environmental Sciences. Poultry litter — a mixture of chicken manure, feathers, spilled food, and bedding material — is an inexpensive and popular fertilizer because it contains nitrogen and phosphorus. But applying more fertilizer than a crop needs can lead to buildup of phosphorus in the soil. Runoff from these fields can increase populations of blue-green algae and undesirable aquatic plants that rob water of oxygen, causing fish kills and odor and taste problems in municipal water supplies. In 1992, Moore discovered that alum (aluminum sulfate) applied to poultry litter greatly reduces phosphorus runoff from pastures. Alum binds to phosphate, forming aluminum phosphate, which is less susceptible to losses in runoff. Moore also found that alum could reduce ammonia emissions in poultry houses. A patent was granted for alum-treatment of poultry litter in 1997, and it was licensed and commercially marketed the following year. To determine the long-term benefits of alum, Moore began two 20-year studies, leading a U of A research team and collaborating with Dwayne Edwards, an agricultural engineer at the University of Kentucky-Lexington. The researchers are studying paired 1-acre watersheds in a commercial beef and broiler chicken operation, along with 52 small plots on university land. They're comparing nutrient runoff following applications of alum-treated poultry litter, untreated poultry litter, and ammonium nitrate, the most common commercial nitrogen fertilizer. The results of the first 10 years of the two studies are now in, and the news is better than expected, according to the article in the November/December 2006 issue of Agricultural Research. Applying alum-treated litter reduced phosphorus runoff by 75 percent from the watersheds and as much as 87 percent from the small plots. Researchers also found that alum reduced ammonia levels in poultry houses by about 70 percent. This is important because ammonia reduces birds' weight and makes them more susceptible to viruses. Alum is known to reduce pathogens in litter and on birds, further contributing to a healthier environment for both workers and birds. Field trials conducted at commercial broiler farms in conjunction with the U.S. Environmental Protection Agency showed that alum lowered litter pH during the first 3 to 4 weeks of chick growth. The lower pH resulted in less ammonia evaporating, or volatilizing, from the litter. Laboratory studies confirmed that alum is one of the most effective compounds for reducing ammonia volatilization. “Less ammonia means healthier, heavier birds,” Moore said. “It also leads to lower energy bills because less ventilation is needed.” Moore also found that forage yields were higher with alum-treated litter than with untreated poultry litter or ammonium nitrate. “Yields of tall fescue fertilized with alum-treated litter were higher,” Moore said. “Grass tissue analyses indicated that the good yields were due to increased nitrogen availability, since alum-treated litter contains more nitrogen than untreated litter. We hypothesized that this was because of reduced ammonia volatilization.” In previous studies by Moore and colleagues, alum-treated litter reduced runoff of heavy metals--such as arsenic, copper, and zinc--by about 40-50 percent and of naturally occurring estrogen by 42 percent. This research indicates that alum-treated poultry litter can be a long-term, sustainable solution to the phosphorus runoff problem, Moore said. Alum is one of the few cost-effective “best management practices” that improves air, soil, and water quality while increasing both poultry production and crop yields. Each year, over 600 million broiler chickens are grown with alum, and its use is rapidly expanding.
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