Farmland across the Chesapeake Bay region is overloaded with phosphorus, a new study by an environmental group finds, indicating that the bay's waters are being polluted by excessive use of animal manure and sewage sludge as crop fertilizers.
In a report released Tuesday, the Environmental Working Group says soil data on file at universities show that in one of five counties in the six-state watershed, more than half of all soil samples tested are overloaded with phosphorus, a nutrient blamed for fouling the bay's waters. In half the counties, more than half the soils tested already had all the phosphorus needed to grow crops.
The Washington-based environmental group says its findings show that none of the six states in the bay watershed or the federal government have done enough to curb pollution from overfertilization of croplands. It's calling for strict, region-wide limits on the use of manure, sludge and fertilizer on already overenriched land.
Topping the report's list of counties with overloaded soils is Worcester County on the Eastern Shore, where Maryland's poultry industry is concentrated. Eighty percent of the soil samples taken there showed excessive phosphorus levels. Nearby chicken-raising counties also showed similarly high percentages: with Somerset at 77 percent, Wicomico with 73 percent and Caroline with 72 percent.
The group's report comes as Maryland and the other bay states work with the Environmental Protection Agency on a "pollution diet" for accelerating cleanup of the Chesapeake, which suffers from an excess of nutrients and sediments. The states submitted their cleanup plans last week to EPA, which expects to make final its pollution reduction orders to all the state by month's end.
In Maryland's plan, state officials pledged for the first time to take steps to address what they called the phosphorus "imbalance" by tightening limits on application of manure and sludge on land with already high levels of the nutrient. But other states have not proposed similar changes.
"This is a regional problem," said Rebecca Sutton, a senior scientist with the group. And though it's one that state and federal officials widely acknowledge, she added, no state is making a concerted effort to collect data on phosphorus levels in its soils, much less prevent the problem from worsening.
J. Charles Fox, EPA's senior adviser on the bay, called the environmental group's recommendation "sound" and consistent with recent scientific findings. He said federal regulators would work over the next year with states to develop ways of limiting fertilizer use in areas where soils are high in phosphorus.
About 45 percent of all the phosphorus getting into the bay comes from agriculture, by EPA estimates. More than half of that comes from manure generated by livestock — notably chickens on the Eastern Shore — and from sewage sludge generated by urban and suburban wastewater plants, and then used as fertilizer on some farm fields.
Maryland and other states have guidelines that are supposed to prevent phosphorus from being applied to fields where the nutrient is likely to wash off or leak into water ways. But the environmental group's report says the "phosphorus site index," as the guidelines are called, screens out only a small fraction of the fields at risk of polluting.
"The index isn't working," Sutton said. "It actually permits disposal of manure on soils that would be called excessive, that have way more phosphorus than they need."
Indeed, phosphorus levels went up in the soil of some heavily agricultural Maryland counties from 1997 to 2002, the report says. Phosphorus concentrations in waterways on the Delmarva Peninsula are among the highest in the nation, according to the U.S. Geological Survey, and levels of the nutrient in the Choptank have increased over the last three decades.