You can't order one from your dealer today. But robotic tractors could be in farmers' fields within three years, according to industry experts.

On-board computers already have the capability to control many tractor functions. Add a little more hardware, a GPS-powered guidance system, some navigational software and you've got a tractor that doesn't need you warming up the cab seat. And, ultimately, it doesn't even need a cab.

Researchers at the University of Illinois (U of I) experimented with a robotic tractor this summer. "We autonomously planted and cultivated a crop of soybeans," says John Reid, U of I ag engineer in charge of the project.

The experimental tractor was programmed to start itself, drive out of the building where it's stored, drive to the field, plant a three-acre research plot and return to the building.

You can watch a video of the robotic tractor by going to the U of I website at www.age.uiuc.edu/oree. Click on "Autonomous Planting of a Crop" and when that file opens, click on the photos. If you don't have the software on your computer to watch video, a software download is on the site.

"During the course of planting we had some software problems and the tractor wasn't turning correctly," says Reid. "To test the accuracy, once we had the problems solved, we replanted the same area. When the seed emerged, the accuracy was so good the field looked like it was just a heavy plant population. Where there was an error, it was 111/42 -2", which is basically the limit for the GPS system we were using."

Reid thinks it's unlikely, however, that farmers will turn planting over to a robotic tractor. "It's more likely that an autonomous tractor will be used for tillage trips, where accuracy isn't as important," he says.

But planting with a robotic tractor would have definite advantages, he adds. "You don't need marker arms, which can reduce the cost of a planter by more than $10,000. And since you no longer rely on markers for your planting pattern, you can program the tractor to plant the field in the most efficient manner. It's not important that the field be planted in sequence, just that it all gets planted."

How quickly you'll see a robotic tractor depends on how badly farmers want them, according to George Huber. He's sales and marketing manager for Precision Agricultural Systems at Trimble Navigation Limited, one of the leading providers of navigation equipment.

"Robotic tractors could be feasible within three years if there's a marketing opportunity," he says. "True robotic tractors will be an evolution from the automated guidance systems that are being put on tractors today."

Reid and Huber both note that safety, not technology, may be the real test of robotic tractors hitting the market. Right now, driverless tractors are banned in some states.

Robotic tractors can be programmed to shut down under certain conditions. "We wanted a minimum of six satellites available for GPS readings to get maximum accuracy," says Reid. "Sometimes there would be less than that and the tractor would just stop and wait."