Mark Dallmann figured he could increase soybean yields by narrowing his rows. But this dyed-in-the-wool ridge tiller wasn't about to knock down his ridges every other year and lose the ridge advantage he'd worked years to establish.

So Dallmann, Lake Lillian, MN, devised a system that lets him plant corn in 30" rows and drill beans in narrow rows while leaving the ridges intact.

"I talked to farmers who were using no-till drills to drill into ridges, but felt I could build something for less cost," he says.

His simple system starts with a homemade deridger made with Hiniker row cleaners to remove crop residue and scrape the ridge tops. Each is followed by four rotary hoe wheels set 4" apart to loosen a 16"-wide band of soil on the ridge.

"We used to have all the deridging equipment hanging right on the planter, but found it works better if we deridge at least a half-hour before we plant," Dallmann reports. "We can actually start when it's a little wetter."

He plants corn with an eight-row Deere 7000 planter equipped with a ridge guider.

Having the deridger as a separate tool and using different machines for planting means Dallmann can prepare soybean and corn fields and plant in whichever field he decides is ready.

"We used to watch everybody else field cultivating for two days before our system would work. It drove me nuts watching them work when I couldn't," he says.

To put narrow-row soybeans on 30" ridges, Dallmann decided to drill two rows on each ridge. The trick was to get those rows placed so they're not too close together but not so far apart that he couldn't cultivate.

"I decided on an 8" spacing, so each of the twin rows is 4" off center," he explains.

His row middles are still open, so he can use the same cultivator in both corn and beans. He feels the open row middles help keep white mold in check, too.

Dallmann built his twin-row ridge drill by mounting 18" Aschermann Vantage 2 coulters and seed-delivery tubes on a homemade double-bar toolbar. Coulters on the front bar plant one side of the ridges and those on the rear bar plant the other.

The coulters are mounted 23 degrees off perpendicular to the ground, so they slant into the ridge. They're offset seven degrees to make an opening for the seed tube.

Seed is metered into the drill units by a Flexicoil 1720 air cart.

To plant at a uniform depth, Dallmann made gauge wheels from old cultivator gauge wheels. They also close the seed furrows.

"These are steel wheels with rubber on them, similar to those on a Case-IH planter. With the seed going in at an angle, it does not take much down pressure to close the furrow back."

After bean harvest, he uses the air cart and toolbar to apply fertilizer for the coming corn crop.

"I deep-inject all of the nitrogen, phosphate and potash for my corn crop in two dry bands on each ridge," Dallmann explains.

He readjusts the coulters and resets the depth gauge wheels, which are adjustable in half-inch increments, so one fertilizer band is 4" off center and 2" deep and the other is 6" off center and 5" deep. Forty percent of the fertilizer goes down through the shallow injector; 60% goes into the deeper band.

Dallmann uses an eight-row ridge cultivator made by B&H Manufacturing, Jackson, MN. He had to widen tunnel shields on the cultivator to cultivate the twin-row beans.

"The standard shield is 7" across and I widened these to 16"."

He starts each year with new 16" cultivator sweeps and cultivates his 600 corn acres twice before moving to soybeans.

"The 16" sweeps are well-worn by then," says Dallmann. "To make sure I don't prune too many soybean roots, though, I cut the sweeps back to 10" wide before I cultivate beans. With this smaller sweep, I'm not doing a lot of ridge rebuilding, but it still cleans the weeds from the row middles."

Harvesting the twin-rowed beans is no problem.

"We use a flex head and the beans run right through. My brother, Brad, runs the combine and says they feed in better than in single rows."

Single and double soybean rows yielded about the same the first year (1996), Dallmann reports. In 1997, twin-row beans looked better, but his check plots were hailed out.

Last year, all his beans were Roundup Ready varieties planted in double rows. The average yield: 56-bu/acre, his best ever.