11/30/2013 7:00 AM
By Dennis O’Brien USDA Agricultural Research Service
BELTSVILLE, Md. — USDA researchers in Bowling Green, Ky., have found that a unique approach to cleaning up feedlot operations — the use of geographic information systems, or GIS, spatial mapping technologies to track how contaminants flow through the soil — offers its own set of benefits.
Cattle feedlots can produce excess concentrations of nutrients, antibiotics and microorganisms that sometimes end up in surface and ground waters. Cleaning up such damage is costly, and the question is how to apply resources to the right areas.
Scientists Kimberly Cook and Karamat Sistani with the Agricultural Research Service, Animal Waste Management Research Unit, along with collaborators at Western Kentucky University, used GIS technology to measure nutrients, bacteria and pharmaceuticals given to cattle that were found in soil samples collected from a 5-acre feedlot used to grow out weaned calves.
The researchers analyzed the soil for nutrients, including nitrogen and phosphorous; antibiotics used to treat cattle diseases and enhance growth; and microorganisms commonly used to indicate fecal contamination in waterways and soils including Escherichia coli, Bacteroides, and Enterococcus. The study was one of the first to simultaneously measure all three types of contaminants — nutrients, antibiotics and indicator microorganisms — and use GIS technology to map contaminant distribution patterns.
The results, published in the Journal of Environmental Quality, showed nutrients, microorganisms and antibiotics all largely stayed in the feeding area at the top of the site’s 4-degree slope. They were distributed in a similar manner with no distinct flow patterns.
Results also showed that GIS mapping is one of the best tools available for determining how contaminants have spread, identifying contaminated areas and deciding on which areas need attention. The findings also suggest that cleaning up the site may be more manageable than previously thought, with efforts focused on remediation of the feeding and nearby grazing areas where contaminants were concentrated.