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CORVALLIS - You're driving through the Willamette Valley and you see dairy farms with corn that looks like it was planted in a lawn. There's green grass growing all around.

Mike Gangwer did that.

The Oregon State University extension dairy specialist planted ryegrass in the cornfields. The ryegrass helps take the stink out of manure and prevents water quality people from raising a stink about manure runoff into streams or underground water supply.

Gangwer is Marion County dairy extension agent and the dairy specialist for the 160 dairy farmers in the eight Willamette Valley counties. Aboard his Honda four-track, he becomes the Johnny Appleseed of "relay cropping," this year seeding more than 255 acres of cornfields to ryegrass.

"Relay cropping" means planting annual ryegrasses anywhere from corn planting time up until the corn is 18 inches tall. After the corn is harvested, the ryegrass remains to sponge up any liquid manure the dairy producer sprays on the land during winter.

The cover crop of ryegrass also reduces soil erosion, giving the farmer a sod base instead of empty corn ground subject to nutrient runoff into streams or underground water supplies. Also, the ryegrass will "scavenge nutrients" from the manure and from fertilizer left in the field after the corn harvest, Gangwer said. That makes the ryegrass a good source of feed for heifers and cows in spring.

"There are no losers when relay cropping with ryegrass - except the inorganic fertilizer (sales people)," Gangwer said. "Relay cropping helps soil stewardship, provides wildlife cover and safeguards water quality. It's good insurance for the producer who wants to stay in compliance with the federal Clean Water Act and Oregon Confined Animal Feeding Operation rules.

"In OSU experiments on these dairy farms, we found that the ryegrass removed 310 pounds of nitrogen per acre from the soil profile - nitrogen that could have leached into groundwater," he said.

Relay cropping has economic payoff, too. Ryegrass seed, which is plentiful in the Willamette Valley, costs only about $8 an acre. "I've seeded up to 30 acres in five hours with my four-track," he said. "But farmers could use a spinner-spreader behind the corn planter and easily seed 120 acres a day."

Gangwer said fields will yield up to five tons of ryegrass dry matter an acre worth at least $100.

There's an aesthetic payoff, too. Instead of seeing bare corn fields this winter, you'll see green. And the manure won't smell for long, because there is green grass to suck it up.