A Maryland farmer who raises chickens for poultry giant Perdue Farms did not discharge pollution into a nearby river, a federal judge ruled Thursday in a case that had been closely watched by environmentalists and the poultry industry. U.S. District Judge William Nickerson sided with Alan Hudson in a 50-page ruling, saying a New York-based environmental group that sued the farmer and Perdue for pollution had failed to prove its case. The organization, Waterkeeper Alliance, alleged that chicken litter from the Hudson Farm in Berlin was discharged into a river that ultimately flows into the Chesapeake Bay, and that Perdue, which owns the chickens and monitors their growth, should be responsible for the pollution.