Jim Colwell knew exactly what he wanted in a soybean drill. When he couldn't find one on any dealer's lot, he went home and built it.

Colwell wanted a heavy-duty drill that would work in any tillage situation and carry enough seed to minimize refilling time. And he wanted to drill in 15" rows, rather than 7.5, 10 or 20".

For top hopper capacity, he centered his home-built soybean drill around a Flexicoil 1720 air cart.

"It holds a total of 172 bu of soybean seed. That lets me plant up to 160 acres without refilling," says Colwell, of Dallas, IA.

For speeding up refilling, he usually uses bulk seed, too.

To put seed into the ground, Colwell mounted 24 Great Plains planter units on a 30' Case IH hydraulically folded toolbar that was salvaged from a 12-row, 30" planter.

The toolbar mounts on a three-point hitch on the rear of his air cart. Putting the planter bar behind the cart made the train shorter than if he'd mounted the toolbar on the tractor and pulled the cart behind.

"It's easier to manage this way," he comments.

The air cart meters seed to the planter units through three distribution manifolds.

Colwell looked at a couple of types of markers to help him keep his 15" rows straight. He finally settled on Kinze tri-fold markers.

"They fold flat, so I don't have to be as careful around trees and other overhead hazards."

To help lift the toolbar and keep weight off the air cart, Colwell added a pair of lift-assist wheels from a John Deere planter.

"These arch up, giving plenty of clearance over the drill units," he explains.

"The original lift-assist wheels from the toolbar were designed for 30" rows. There was plenty of room for them between the row units when spacing was 30". But they were too big to go between the Great Plains units spaced at just 15", so I wasn't going to be able to raise it high enough to keep it off the ground."

One of the air cart's best features, Colwell continues, is its two hoppers, each with its own metering system.

"There are a number of ways I could use this technology," he says.

For example, he often fills the tanks with different varieties so he can switch from one to another when he moves from field to field.

"I sometimes have a regular variety in one tank and a herbicide-resistant variety in the other. Then I can go right from a field where weed pressure is light into one where weed problems justify Roundup or STS chemistry, without having to clean out the planter and reload. It saves a lot of time."

Colwell also uses the air cart to deep-inject fall fertilizer. He equipped his three-point anhydrous toolbar with fertilizer injection coulters. To apply fertilizer in one pass, he mounts the toolbar on the cart's hitch and pulls an anhydrous tank behind.

Looking ahead, he's thinking of adding a hydraulic drive to replace the cart's mechanical system.

"That would allow me to use electronics to control seed metering or fertilizer application rates. It would be an easy step to turn control of application rates over to a computer program based on information gathered through GPS-based soil or yield maps."