Farmers Use Chicken Excrement Laced with Arsenic to Grow Fruit and Vegetables

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Fields amended with poultry excrement can accumulate significant levels of arsenic, according to studies by USDA-Agricultural Research Service (ARS) scientists and associates. These findings provide key information about the agricultural pollutants that can build up in agricultural soils over time—and possibly migrate into nearby streams and rivers.

Poultry producers have sometimes supplemented chicken feed with roxarsone, a compound containing arsenic, to control parasites and promote weight gain. Most of this arsenic is excreted by the birds and then becomes mixed in with sawdust and other litter materials used in poultry houses. Farmers typically use the litter as a nutrient-rich—and free—fertilizer for amending their crop soils.

Because poultry manure is rich in nutrients, greater than 90% of poultry litter is land-applied as fertilizer (Jackson and Bertsch, 2001; Morrison, 1969; Moore et.al., 1998). Although Rutheford et al. (2003) showed that soils receiving long-term poultry litter application also had high levels of water-extractable Arsenic and that Arsenic appeared to be sorbed to iron oxyhydroxides in some soil types, the ultimate fate of Arsenic derived from roxarsone as well as the controls on Arsenic movement in the environment are largely unknown (Christen, 2001).

For two years, researchers at the ARS measured arsenic levels in runoff that flowed from farm fields into seven drainage ditches in the Delmarva (Delaware, Maryland, Virginia) Peninsula, an area dominated by large-scale poultry production for decades. Runoff measurements indicated that annual arsenic losses from these fields could range from 0.004 kilograms per hectare to 19 kilograms per hectare. Runoff with the largest arsenic loads was recorded in a ditch closest to a main point source of the contaminant—a shed where litter was stored.

They team also tracked phosphorus runoff, as it are known to interact and compete with arsenic. During storm events, both pollutants exhibited similar behavior. However, their concentrations differed significantly between ditches and showed no seasonal patterns. This suggests that management practices for phosphorus are unlikely to be applicable to arsenic.

This study highlights the importance of controlling point sources of arsenic and other chemicals and suggests that management practices—such as properly storing dry litter and controlling litter spills outside storage facilities—can help protect local regions from the migration of arsenic and other agricultural pollutants.

Results from this research will be published in the November/December 2010 issue of the Journal of Environmental Quality, a publications of the American Society of Agronomy, the Crop Science Society of America, and the Soil Science Society of America.

The Journal of Environmental Quality is a peer-reviewed, international journal of environmental quality in natural and agricultural ecosystems published six times a year by the American Society of Agronomy (ASA), Crop Science Society of America (CSSA), and the Soil Science Society of America (SSSA). The Journal of Environmental Quality covers various aspects of anthropogenic impacts on the environment, including terrestrial, atmospheric, and aquatic systems.

The American Society of Agronomy (ASA) www.agronomy.org, is a scientific society helping its 8,000+ members advance the disciplines and practices of agronomy by supporting professional growth and science policy initiatives, and by providing quality, research-based publications and a variety of member services.

Source

Clinton D. Church, Peter J. A. Kleinman, Ray B. Bryant, and Lou S. Saporito USDA–ARS
Arthur L. Allen. Occurrence of Arsenic and Phosphorus in Ditch Flow from Litter-amended Soils and Barn Areas. J. Environ. Qual. doi:10.2134/jeq2009.0210. Published online 10 Aug. 2010.

The full article is available for no charge for 30 days following the date of this summary. View the abstract at https://www.soils.org/files/publications/jeq/abstracts/39-6/q09-0210-abstract.pdf.

American Society of Agronomy (ASA) Released: 8/12/2010 5:00 PM EDT

Key concepts: arsenic, food, runoff