Title: Metrics for nitrate contamination of ground water at CAFO land application sites Authors
Submitted to: Technical Report
Publication Type: Government Publication
Publication Acceptance Date: April 1, 2009
Publication Date: June 30, 2009
Citation: Moore Jr, P.A., Brauer, D.K., Striz, E., Dorsey, N., Hutchins, S. 2009. Metrics for nitrate contamination of ground water at CAFO land application sites. EPA 600/R-09/044 Technical Report. Available: http://www.epa.gov/ada. Interpretive Summary: Animal manure is routinely applied to farmers' fields according to a nutrient management plan (NMP), as a strategy to reduce the likelihood of nitrate leaching into ground water and phosphorus runoff. The objective of this research was to determine if the application of dairy manure according to a state approved NMP would protect ground water from nitrate contamination. ARS scientists from the Booneville and Fayetteville locations working in conjunction with EPA scientists conducted a year-old study on a dairy farm in northwest AR. Soil water samples collected from field receiving effluent (liquid manure) from the dairy farm's holding pond were found to contain excessively high levels of nitrate. A substantial amount of the nitrate in these soil water samples appeared to be derived from direct manure deposits when the farmer used these fields during the winter as a high animal use area. Results indicate that direct deposits of manures to application fields need to be considered when formulating NMPs.
Technical Abstract: Land application of manure from concentrated animal feeding operations (CAFOs) may lead to contamination of ground water with nitrate. CAFOs routinely apply animal manure according to nutrient management plans (NMPs). The objective of this research was to determine if NMPs protect ground water from nitrate contamination. A study was conducted for one year on a dairy farm in northwest Arkansas. Four plots, each equipped with a 1 m deep lysimeter, were established in two fields which are irrigated annually with effluent from the farm's manure holding pond. The amount of N applied via effluent averaged 280 kg N per ha. Soil water from lysimeters and plant samples were collected weekly and analyzed for nitrate. Nitrate levels in soil water samples were excessively high. Beginning in November, it was observed that the farmer utilized these same two fields as a loafing area for his cows from several months beginning in November. Significant deposition of manure occurred during this time. Researchers estimated that as much as 840 kg N per ha were being added via direct manure deposits, based on the observed cattle stocking rate, duration of stocking and published estimates of N excretion. Thus, the total annual N additions to these fields were approximately 1100 kg N per ha. Such levels of N additions were more consistent with the observed levels of nitrate in the soil water samples. Results indicate that direct deposits of manures to waste application fields need to be considered when formulating NMPs. Leaf tissue nitrates were highly correlated with nitrate concentrations in soil water samples. Thus, leaf tissue nitrate levels were a good indicator of nitrate contamination in the soil water samples.