You might say Larry Nielson looks at the world a little backwards. At least that's true when he hatched the idea of building a self-propelled sprayer from an old International 915 combine chassis by reversing the drive train.

As a mechanized ag major at South Dakota State University, Nielson admits he likes the challenge of reinventing farm equipment. In fact, he's also built a homemade 11-row, 24-in., no-till planter.

But back to the sprayer. Nielson stripped down the combine to the frame and bolted on a Case tractor front axle for conventional steering, and turned the controls around. He then added the combine's 407-cu.-in. engine to the back, now front, of the frame. He added a cab to the rig from a John Deere 8630 tractor.

Next, he mounted a 750-gal. tank from an old Ag-Chem sprayer directly behind the cab. Behind that he mounted another 100-gal. tank that he fills with water to rinse the sprayer lines. All this is tied together with a new Raven controller.

To finish off the sprayer, he had a tailor-made 88-ft. boom built at River Bend Industries in Moorhead, MN, at a cost of $8,600. “Normally, they build 90-ft. booms, but I had them shorten it by 2 ft. to accommodate my planter rows. They also had to adjust hinge points,” says the Tulare, SD, farmer who grows 1,000 acres of mostly corn and soybeans in the east-central part of the state. Side booms are 32 ft. wide and hinged in the middle.

Total cost for the shop-built sprayer ran just under $30,000. “I figure it paid for itself the first year, if I based the price off the cost of hiring a custom sprayer. It was a good economic alternative to a factory sprayer,” Nielson says.

Although there's probably potential to do some custom spraying with the new rig, Nielson hasn't pursued that because of how it would affect his insurance rates.

A downside to the sprayer for some farmers might be that its road transport width is 16 ft. “But that's not a big deal for me because there's hardly any traffic out here and I don't have any bridges to go over,” he says.

Would he change anything the next time around? “Sure. In hindsight I'd make it 100 ft. wide because with the wide wheel base of the rig, it's very stable in the field,” he says.