The tractor weaves to ride the field's dips and rises while perfectly hugging the row previously cut by its black-clawed tiller, creating a seamless pattern of turned soil.
But the person in the cab has nothing to do with this precision. Aided by a computer and a Global Positioning System — a constellation of Earth-orbiting satellites — the vehicle is driving itself.
All the farmer has to do is turn the tractor around when it reaches the end of the field.
The use of technology has increased in the past few years as farmers try to cut costs to compensate for relatively stagnant crop prices. Infrared sensors control how much fertilizer is applied. Retinal imaging tracks cattle. On the horizon, perhaps, are tomato-picking robots.
Experts estimate that up to 15 percent of farmers now have GPS precision-controlled tractors or combines, which first began hitting the fields in the late 1990s.
"It's the difference between making money and not making money," said Dave Mowitz, machinery and technology editor for Successful Farming, a national farm publication based in Des Moines, Iowa.
AutoFarm, a company based in Menlo Park, Calif., adapted a $40,000 GPS system for agriculture from an automatic aircraft-landing system. About 300 have been sold since the equipment went on the market last spring.
A GPS receiver placed on top of the tractor pulls in locational radio signals from satellites and a ground station fed by satellites. A computer inside the tractor memorizes the coordinates of the field and guides the tractor over the same path — for tilling, planting, spraying and harvesting.
"Everybody's been looking at that and saying, 'Gosh, can they do it?"' said Thomas Wagner, who was helping demonstrate the GPS precision-curve system last September at the Farm Science Review near this central Ohio city. "Bring your tape measure and we'll show you we can actually do the curves."
Farmer Ernie Hatfield was impressed with the demonstration, but wasn't sure the price tag was justified for his 50 acres near Bethel in southwest Ohio. "We need it," he said, "but it's probably cost prohibitive."
Expense is one reason technology can be a hard sell to farmers. Some believe that precision-guidance systems make economic sense only for large farms.
"They are slow to adapt," said Joe Malone, who raises hogs near Lancaster and once worked in robotics for Goodyear Corp. "Once you get a farmer that looks at what it can do for him from a standpoint of money — that's all he's looking at. Then he'll buy into that project right now."
For some, like John Ikerd, the farm technology boom doesn't look like a good omen for the future of small-time farming.
Ikerd, professor emeritus of agricultural economics at the University of Missouri, is convinced the new technologies will result in more corporate agriculture and fewer family farms. He thinks decisions about what and how much to plant will be made by faraway corporate officers whose primary focus is maximizing return to shareholders and not necessarily what is good for the land.
Savings come in any number of ways. One is driving over the same route each year to minimize the compaction of soil that can reduce yields. Another is cutting the loss of herbicide to evaporation by allowing farmers to work at night, when winds often are calmer.
"It allows them to farm 24 hours a day if they want to," Mowitz said. "It can be pitch black, and you can be planting your fields."
Still another savings comes from reducing the use of fertilizers and pesticides — as much as 5 percent, estimates Dennis Hancock, an agriculture researcher at the University of Kentucky.
Remote sensing also can reduce the use of fertilizer. Photo-diode sensors mounted on a sprayer absorb the color spectrum being reflected by the plants, and a computer determines how much fertilizer or herbicide to spray. The sensors came on to the scene in the 1980s but have really taken off in the past five years.
"You're putting more on plants that can use more and not putting as much on plants that can't use as much," Hancock said.
A computer/GPS system also produces maps showing where a field is the most and least productive. A farmers can use more seed and fertilizer in less productive areas or take those areas out of production.
As a combine moves through the field threshing corn and spitting it into a bin, a sensor in the bin measures the output while the GPS system marks and records the crop yield in each spot.
The cattle-identification system uses a high-speed digital camera to illuminate and scan the retinas of calves or lambs. The images are loaded into a computer, and a GPS signal tracks the animals from the pasture to the slaughterhouse. The equipment, in use about a year, costs about $2,700.
The system could help quickly identify an animal with mad cow or other diseases, said John Cravens, marketing director for developer Optibrand Ltd. of Fort Collins, Colo. It also provides a profile of each animal, including weight, diet and medical treatment.
More technologies are on the way. Not yet in the fields is the tomato-picking robot. Developed by Ohio State University researchers with a $100,000 grant from NASA, the single-armed robot has a prosthetic hand and a lipstick-sized camera and is mounted on a portable platform.
Researcher Peter Ling said the camera spots tomatoes and determines their size and color even if they are partially hidden behind leaves or stems. Using a suction cup and fingers that employ a loose grip, the hand plucks the tomatoes from the vine and drops them into a bin.