Long before there was something known as the "nutrient reduction strategy," Rob Stout was figuring out ways to keep the soil in place on his southeast Iowa farm — not because of threats of heavy-handed government regulation or litigation, but because it was the right thing to do.

A devout no-till farmer since the early 1980s, Stout expanded his conservation practices to include cover crops six years ago.

"We’ve had some really wet springs, and we just weren’t holding our soil like we wanted to," said Stout, who grows corn and soybeans on 1,000 acres in Washington County. He seeds cover crops on about 600 of those acres.

"We farm a lot of rolling ground. We make sure we cover everything more than 2 percent slope with cover crops," he said.

In addition to limiting soil erosion, cover crops keep both nitrogen and phosphorus from escaping into waterways, which are key goals of the...