It was the drought of 1988 that got John Wilken thinking about the wisdom of draining his “liquid assets.”

Wilken, who farms in east-central Illinois, had partly tiled a field before the season started. That dry summer, the undrained portion of his field produced significantly better corn than the drained portion. “That tripped a trigger in my mind, that we should be conserving some of our water for when it's needed,” he says.

Today, Wilken does just that. He controls how much — and when — tile drainage water leaves 340 acres of flat cropland in Iroquois County.

Using eight outlet control structures in his main tile lines, Wilken can raise and lower the water table depth in two fields. He holds back water in the soil all winter, when drainage isn't needed for crop production, then releases it about two weeks before field operations begin in the spring.

After planting, he raises the outlet height above the tile depth in order to capture some of the rainfall that would ordinarily drain out. Just before harvest, he drops the outlet back down to the tile depth. In November, after fall strip-tillagefertilizer application, Wilken raises the outlet height once more, lifting the water table almost to the surface.

This practice — known as drainage water management, or

In 2007, the five-state Agricultural Drainage Management Coalition began side-by-side comparisons of conventional and controlled drainage on 20 farms in Ohio, Indiana, Illinois, Iowa and Minnesota. These demonstrations “will really accelerate our understanding” of the practice, and how it performs across a variety of climates and soils, Helmers says.

In Illinois, where more than 50 on-farm demonstration systems have been installed, drainage water management has cut tile outflow by 40%, Pitts says. As tile water volume drops, so does nitrate loss — especially during the winter, when half of annual drainage flow occurs in the eastern Corn Belt.

IN THE NORTHERN Corn Belt, the benefits will probably be more modest, says Gary Sands, a University of Minnesota Extension engineer. There, about 70% of annual tile flow occurs from April to June, when growers need drainage most. “So we have a smaller window of opportunity to manage drainage water here,” he says.

Still, northern states could see “20-40% reductions in the volume of drainage water” and corresponding nitrate loads, Helmers says.

John Wilken grows corn and soybeans on 1,900 acres near Onarga, IL. In 2002, he installed controlled drainage in a 160-acre field and a 180-acre field. The improvements were cost-shared under the

Maintaining the water table 2 ft. below the surface, rather than the typical 4 ft., retains up to 1.5 in. of additional water in the soil, Pitts says. “This equals about six days' water supply for a corn crop in July, and thus, could have a significant crop production benefit.”

On suitable land, a drainage management system amortized over 15 years at 6% interest would cost $7-9/acre, according to Leonard Binstock, executive director of the Agricultural Drainage Management Coalition. Yield increases of just 2 or 3% could pay for the system. Controlled drainage is also eligible for EQIP grants, and additional incentives were included in the new farm bill.

Pitts contends that drainage management “is arguably the conservation practice with the highest benefit-to-cost ratio for reducing nitrate loss.” Wilken agrees: “I feel my yield increases have paid for the investment. And we're doing our part to keep nitrates from ending up in the Gulf of Mexico.”

If you're planning to upgrade your drainage system or install a new one, think about designing it “with drainage water management in mind,” Sands suggests.

WATERPROOFING

Brian Hicks could see the problem on his yield monitor.

In a fertile, low-lying cornfield, there was an area that lagged the rest of the field by 25-30 bu./acre, year after year. “That portion of the field always dried out in July,” says Hicks, who raises corn, soybeans and grass hay near Tracy, in southwest Minnesota.

The flat bottomland near the Cottonwood River was also slow to dry out in the spring. Hicks wished he could “get the water drained out in the spring, and then save the water later in the season when it got dry.”

Next Page: Where does the retained water go?