WASHINGTON – Significant questions are being raised about the data used by the Environmental Protection Agency (EPA) to develop and implement the Chesapeake Bay Total Maximum Daily Load (TMDL) rule that appears in a third-party study conducted by LimnoTech and released by the Agricultural Nutrient Policy Council (ANPC).

In a study titled Assessment of the Effects of Conservation Practices on Cultivated Cropland in the Chesapeake Bay Region, developed by the US Department of Agriculture, very different estimates of pollutant loads to the Chesapeake Bay are reported compared to EPA’s data.

“Basically, we have two different agencies in this administration studying the same thing but yielding completely different results,” said Ashley Lyon, deputy environmental counsel for the National Cattlemen’s Beef Association. “USDA’s report clearly shows that farmers and ranchers have already significantly surpassed EPA targets for reductions in sediment and phosphorus.”

The LimnoTech report found many discrepancies between USDA’s report and EPA’s data. The LimnoTech study found USDA and EPA make different assumptions about animal-feeding operations (AFOs) and confined animal-feeding operations (CAFOs). EPA attempts to model loads from the CAFO production areas, where animals are housed and manure stored, while USDA does not. Both EPA and USDA appear to model manure application on cropland on a nitrogen basis. USDA estimates 38% of cropped acres have manure applied. According to the LimnoTech study, it is not possible to determine from the available EPA documentation how much of the cropland receives manure.

“Given the seriousness of this issue and potential regulatory consequences to agriculture, it is absolutely imperative that a more accurate study is conducted,” Lyon said. “The regulations that will likely be derived from EPA’s flawed model will put farmers and ranchers out of business. This regulation not only impacts agricultural producers living on the Chesapeake Bay watershed but lays the foundation for all watersheds. Sound science must be the basis for any regulations.”

The USDA model framework seems to more accurately represent Chesapeake Bay watershed agricultural operations and management practices, including consideration of crop rotations, varying levels of tillage (no-till, mulch till, conventional till) and actual nutrient management practices, according to the LimnoTech study.