DES MOINES, Iowa (AP) – A Des Moines utility has for years engaged in a bitter struggle to clean up drinking water that comes from rivers teeming with agricultural pollutants, filing lawsuits, proposing legislation and even public shaming to try to force farmers to reduce runoff from their fields.

None of it has worked, so Des Moines Water Works is trying a less combative approach – inviting farmers to learn the latest techniques for reducing pollution at riverfront plots of corn and soybeans in the sprawling park where the utility filters the city’s drinking water.

“I think it’s great to have the farmers out here and show what can be done,” said Jessica Barnett, who oversees management of the 1,500-acre (2.3-square mile) park little more than a mile from downtown.

It’s a surprising turn in a long-running dispute between the state’s dominant industry and a utility that supplies drinking water to 600,000 customers in Iowa’s largest metro area.

Des Moines Water Works has complained for years that nitrates and phosphorous from farm fertilizers pour off fields, leaving rivers so polluted that the utility fears even its sophisticated and costly equipment can’t purify the water. The utility’s efforts to hold some upstream counties legally liable for the pollution have failed, and Republicans who control the legislature and governor’s office have repeatedly rejected regulation, instead supporting voluntary programs too limited to result in real improvements.

That history makes the deal between Landus, the state’s largest farmer-owned grain cooperative, and Water Works all the more surprising. Or as Matt Carstens, the president and CEO of Landus, put it: “This is an unlikely partnership.”

In some ways, Carstens and Water Works CEO Ted Corrigan said the new initiative is possible only because the earlier, more confrontational approaches failed.

“Whatever we’ve tried in the past hasn’t been as successful as this could be,” Carstens said.

Under the plan, Landus has planted corn, soybeans and a cover crop of rye and red clover on three plots totaling about 12,000 square feet near a bend in the Raccoon River that, along with the Des Moines River, meets the city’s water needs.

Landus plans to bring in about 500 farmers through the summer to examine the plots and learn how they can confidently scale back their use of fertilizer, with more advanced monitoring and by planting cover crops that grow alongside the main crop and naturally infuse the soil with nitrate.