GPS-based technology has matured into an integral and necessary part of farming in the eastern Corn Belt, at least for some families.

Ed Leininger purchased his first GPS (global positioning system) receiver and yield monitor in 1995. It was an interesting technology toy at the time, with possible applications. Today, it's fully integrated into the farm.

Ed and his family grow 2,600 acres of corn and 2,000 acres of soybeans on 184 separate fields in heavily urbanized North Central Indiana. Their farm, at Mishawaka, is adjacent to the suburbs of South Bend, IN.

Things changed in 1999 when Ed's daughter Brenda began integrating the GPS information with detailed tracking of field production and mapping. About the same time, her older brother Jeff got involved. He has a background in information technology and the technical skills to make the software and data streams work together.

They also bought a light bar that year for guiding equipment with the aid of GPS. That investment paid for itself the same season, Ed says.

The farm has also been growing. Dozens of fields have been added since 1995, mostly as neighbors retired. Although typical field size is 30-35 acres, some are as small as two acres.

“We manage them with maps, and each one is treated separately,” Ed says.

Their basic GPS system is an Ag Leader PF3000.

It's factory-installed on one of the two combines, which always run side by side. While mapping, it records yield and field notes made by the operator. This year, they purchased a second GPS system with a light bar. It can be moved to a new machine in about 30 minutes, and gives them more flexibility.

Brenda downloads harvest information into her computer — maps, yields, notes and bin numbers. Her inventory record is ‘perfect.’

Before doing any fertility work, the family first has soil sampling done on a grid basis, guided by GPS, through their local farm supply dealer, Frick Services. Brenda overlaps yield maps with soil test results, field by field. The blended results take shape as a series of variable-rate prescription maps for fertilizer and lime.

They steer the high-clearance, self-propelled fertilizer spreader with GPS and a light bar across each field, following the prescription from Frick Services. Some of the fertility work is done in fall, during harvest, and some in spring.

They move the guidance system into a 4WD tractor when they're ready to seed soybeans. The system produces perfect rows without overlap or misses. (Ed continues to plant corn without the aid of GPS, but that may change.)

After seeding, they do postemerge weed control guided by GPS and the light bar. Brenda's younger brother Joe also sometimes does patch spraying with GPS. He finds the patches by sight, but has GPS tied into his spray monitor to record each patch application.

The light bar, Joe says, has the clearest advantages. It's more accurate than foam. It's easier driving for the operator. And, it produces a perfect record of what was sprayed where and when.

Ed says, “We saved enough in chemicals and foam to pay for it the first year.”

The bigger economic impact, Ed says, is from the variable-rate fertilizer and lime applications. Over-application is history, and they can afford to give an extra shot in places that can handle it.

“It's taken the bad spots out of the fields, and our yields are coming up because the corn and beans aren't stressed,” he says.

Leininger's agronomist, Matt Lechlitner of Frick Services, Wyatt, IN, agrees.

“There's a big savings with variable-rate application,” he says. “Instead of just putting 2 tons/acre on the entire field, the rate varies and a lower overall average is applied; at the same time, the overall yield improves.”

Some customers buy less fertilizer and less chemical on a per acre basis than they once did. Some buy more. The more precisely the application fits the crop potential, the better the potential return on dollars invested.

“GPS is becoming more popular all the time. All of our trucks have light bars for plotting purposes,” says Lechlitner. “We use it every time we go into a field for soil sampling, scouting, chemical application or fertilizer application.”

The economics of site-specific farming technologies are starting to prove themselves, says Jess Lowenberg-DeBoer, director of the Site Specific Management Center at Purdue University. He estimates that 30% of grain acres in the U.S. are harvested with a combine using a yield monitor, and about one third of these are equipped with a GPS system for yield mapping.

“The light bars with GPS guidance have really seen a boom in the last few years,” he says. “We know that more than half of all custom operators in the Midwest use GPS light bars instead of marker systems. Guidance for anything that needs accuracy has proven to be quite profitable, and has a relatively quick payoff.

“For a producer who already has a GPS and yield monitor, reducing skip and overlap (with a light bar) may give a benefit of $1/acre each year,” says Lowenberg-DeBoer.

In the Eastern Corn Belt, he notes, variable-rate application of lime is becoming popular. “Soil pH management has proven to be quite profitable,” he says. “Depending on what you're doing, our numbers suggest benefits of $3-7/acre each year in a corn-soybean rotation.”

Benefits from an integrated system of site-specific management for corn and soybeans have been substantial. One of the best documented examples, in central Illinois, was a four-year study on four fields in a corn-soybean rotation, where corn was given close attention.

“There was an average increase in corn yield of 15 bu./acre by the integrated package of yield monitoring, site-specific application of lime, P, K and N, with variable-rate planting,” says Lowenberg-DeBoer.

For high management growers, he says, GPS definitely is becoming integrated into the full scope of farming operations.

“It's a matter of finding levers on the particular crops you grow, finding things you can change to help improve your productivity,” he says.