If you've got a large dairy barn near your grain farm, you might smell manure. Or you might smell “moo-lah.”

Dairy manure saved the Koehl family of Hancock, MN, at least $30/acre on fertilizer this fall compared to commercial nitrogen (N), phosphate and potash. And that doesn't count the value of the manure's micronutrients and organic matter.

The Koehls buy liquid manure from Riverview, a nearby dairy operation that milks about 30,000 cows at five sites.

In addition to saving money, “we see a yield benefit from manure, not only in the first year but in the following years, too,” says Mitch Koehl, who raises corn for grain and silage, wheat, kidney beans and alfalfa with his dad, uncles and cousins. The seven-family group also operates a feed supply business, three swine finishing barns and a cattle feed-lot. Despite having their own manure source, “we'll take as much dairy manure as we can get,” Koehl says. “It's an economic advantage for us.”

About 5% of U.S. cropland is fertilized with manure, according to a June 2009 report to Congress by the Agriculture Department. But higher fertilizer prices this decade — and the likelihood of future price hikes — have boosted interest in manure, says Eric Dresbach of Circleville, OH, president of the Midwest Professional Nutrient Applicators Association.

Riverview barns, for example, generate enough manure to fertilize more than 22,000 acres of corn ground a year, yet “our list of guys who want manure is longer than we can supply,” says Brad Fehr, Riverview agronomist. The dairy furnishes low-cost fertilizer to about 50 local growers, he says.

Meanwhile, expanded environmental regulation and “more big barns on little farms are driving the need for a larger land base to apply manure,” Dresbach says.

More manure for sale or exchange is a “great advantage for crop producers,” he says. “If I had a livestock producer near my farm, he'd be my best friend.”

Koehl seconds that: “As crop producers, the dairy is a real benefit for us, both as a place to sell crops and as a source of fertilizer.”

The Koehl family farms land near three of Riverview's dairy barns in west-central Minnesota.

RIVERVIEW SEPARATES MANURE and sends the solids back to the barns for bedding. The liquid manure, which contains about 4% solids, is stored in tarp-covered basins. In the fall, Riverview pumps the fertilizer through hoses to fields up to three miles away, where it's injected into the soil with a tractor that pulls a dragline hose through the field.

Dragline hose application systems cut liquid manure transportation costs and reduce compaction, which is a big concern for grain farmers who receive manure, says Kevin Erb, a University of Wisconsin Extension manure specialist. “A 9,500-gal. manure tanker plus a tractor can weigh 150,000 lbs., which can be a problem in wet soils.”

Riverview takes frequent nutrient samples throughout the pumping period. Crop farmers worry about erratic nutrient ratios in manure, Fehr says. It's one reason manure gave way to commercial fertilizers. But thanks to covered basins and other management practices, “we see little nutrient variation. It's a very consistent product.”

This fall the Koehls bought 700 acres' worth of Riverview manure. On corn silage and dry edible bean fields, the liquid is injected directly into crop stubble. On corn grain and wheat fields, “we work the ground first, then inject manure,” Koehl says.

Because their land is regularly receiving manure, the Koehls soil test most fields every fall. Their soils score in the medium range for phosphorus (P) and potassium (K), allowing the manure rate to be formulated on an N basis. Their typical application supplies about 135 lbs./acre of N available the first year, 65 lbs. P, 200 lbs. K and 3 lbs. zinc. “We don't add any additional fertilizer, except some anhydrous on the end row where they turn the applicator,” he says.

The dairy manure they bought this fall provided nutrients worth at least one-third more than the manure cost, Koehl says. USDA reports that corn growers who substituted manure for commercial fertilizer lowered their fertilizer expense by 37% compared to farmers who used commercial fertilizer only.

THE BENEFITS OF manure for crop yields and soil are well documented, but cash grain farmers should carefully weigh the economics, Erb says. Manure application costs, which are determined by time and distance, may exceed the value of the nutrients, especially with liquid dairy manure. He says, “Manure can pay a big dividend, it can be a break-even or it can cost more than commercial fertilizer. It depends on your location, soil tests and the cost of commercial nutrients.”