A scientist testified that runoff from fields spread with poultry manure accounted for a major portion of phosphorus pollution in a sensitive northeastern Oklahoma watershed.
But an attorney for 11 Arkansas poultry companies who do business there argued Wednesday that geochemist Roger Olsen overlooked nearly 20 other possible sources of pollution, such as coal-fired power plants, urban runoff and cattle operations.
Olsen, who is testifying as an expert witness in the state of Oklahoma's federal pollution case against the poultry companies, developed his findings after analyzing water and soil samples taken from the Illinois River watershed.
The closely watched case, which began in September and has lagged on for months, wrapped up its 24th day Wednesday.
Oklahoma sued the industry in 2005, saying the companies are to blame for polluting the watershed with tons of chicken manure. The companies say the waste is the responsibility of their contract growers, and that the state is trying to tailor science to fit its lawsuit.
During cross-examination Wednesday, Tyson Foods Inc. attorney Tom Green rattled off a list of other possible contaminants he said Olsen left out of his analysis.
Green, who is also representing company subsidiaries Tyson Poultry Inc. and Tyson Chicken Inc., said Olsen failed to take soil or edge-of-field samples near septic systems, nurseries, golf courses or areas where only commercial fertilizers had been used _ suggesting such data might conflict with the state's premise that excess poultry manure is the major cause of pollution in the Illinois River watershed.
As one example, Green said arsenic, which is found in poultry manure, is also present in deposits from coal-fired power plants located within 50 miles of the 1-million-acre river valley.
Green asked Olsen if he had any way to dispute the contribution made from the plants.
"If it was a big contributor, we contend we would have found it in our reference soils," Olsen replied.
Last week, a Cargill executive testified that he didn't check to see if company farmers were following an environmental handbook he helped compile in 2002 that warned them not to spread excess chicken manure on their land because the runoff could pollute area water.
The other defendants named in the lawsuit are Cargill Inc., Cal-Maine Foods, Inc., George's Inc., Cobb-Vantress Inc., Cargill Turkey Production L.L.C., George's Farms Inc., Peterson Farms Inc. and Simmons Foods Inc.
Testimony is scheduled to continue Thursday.