A Cargill executive testified Thursday that he did not 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.

About 30,000 fewer people floated in the Illinois River watershed in 2007 compared with two years earlier, a professor testified Tuesday, suggesting that decades of chicken manure pollution may have made one of the state's top recreational areas less attractive to the public.