A federal appeals court has rejected Oklahoma’s bid to stop poultry growers in Oklahoma and Arkansas from spreading poultry waste in the Illinois River watershed while an environmental lawsuit winds its way through court.

In its opinion issued Wednesday, a three-judge panel of the 10th U.S. Circuit Court of Appeals ruled a federal judge was within his discretion in denying an injunction.

The appellate court said the state failed to link the poultry waste – which is used as fertilizer – to bacteria in the watershed.

The poultry industry argues that cattle and human waste could also be causing elevated levels of bacteria in the watershed. Oklahoma argues the state doesn’t have to prove contamination, only that 345,000 tons of chicken waste dumped there annually “may” cause contamination.

In its ruling, the appellate court did not address the merits of the state’s lawsuit, only that Oklahoma had not proved “irreparable harm” in asking to immediately block companies from dumping their waste.

A trial in the larger lawsuit is scheduled for September.

Oklahoma Attorney General Drew Edmondson is suing 13 Arkansas poultry companies, including Tyson Foods Inc. ( TSN – news – people ), Tyson Poultry Inc. and Tyson Chicken Inc., over the effects of over-application of chicken waste in the watershed. Edmondson said the bacteria contamination was discovered as they prepared for the lawsuit, which was filed in 2005.

State officials estimate the application of untreated poultry waste in the watershed is the equivalent of untreated human waste from between 4.2 million and 10.7 million people. The case is closely watched because it could increase the cost of raising chickens and lead to higher meat prices.

“The people an injunction would have harmed are the hardworking, independent farmers and cattle ranchers who depend upon poultry litter as an economical and beneficial source of fertilizer for land,” Tyson said in a statement.

The appellate court also upheld the lower court’s rejection of two of Oklahoma’s expert witnesses, whose testimony was deemed “not sufficiently reliable” because their work had not been peer-reviewed or published.

“We find no abuse of discretion in the court’s determination,” the panel wrote.

Other companies named in Edmondson’s lawsuit include Cobb-Vantress Inc., Cal-Maine Foods Inc. ( CALM – news – people ), Cargill Inc., Cargill Turkey Production L.L.C., George’s Inc., George’s Farms Inc., Peterson Farms Inc., Simmons Foods Inc., Cal-Maine Farms Inc. and Willow Brook Foods Inc.