Poultry farmers spread three times more phosphorus in chicken manure on their fields than their crops needed, according to records from 62 poultry operations in five counties on Maryland’s Eastern Shore in 2012. This excessive application of poultry manure is a problem because manure is loaded with phosphorus, and applying it to fields that already have more than enough contributes to phosphorus runoff pollution that feeds algal blooms and low oxygen “dead zones” in the Chesapeake Bay. Approximately 75 percent of the phosphorus in chicken manure applied on these farms was over the amounts needed, and 61 percent of the manure was spread on land that already had “excessive” phosphorus levels, based on criteria published by the Maryland Department of Agriculture. Because phosphorus was applied in amounts far higher than what crops used, its concentration in soil increased by an estimated 10 percent by the end of the 2012 growing season.
This analysis by the Environmental Integrity Project is based on field-level data in farm fertilizer management reports called Annual Implementation Reports submitted to the state by 62 poultry operations that spread manure on their own cropland in Caroline, Dorchester, Somerset, Wicomico, and Worcester counties. The data is incomplete, because reports from hundreds of other poultry operations show that about 85 percent of poultry manure is shipped offsite to crop farms and other locations within the Eastern Shore, and crop farms are not required to disclose field-level phosphorus application rates in annual reports.