Satellites help farms lessen waste, harvest

By REBECCA ZEIBER
Collegian Staff Writer

The Department of Defense has used Global Positioning Systems (GPS) for decades to determine precise locations on Earth. In the last decade, this technology has spread to agriculture.

By applying GPS to farm equipment, a technique called "precision agriculture" has developed. It may lead to less environmental impact and may reduce the amount of pesticide and fertilizer farmers must apply to their land, said David Wagner, assistant professor of agricultural and biological engineering.

"The emerging technology in the world today is going from map-based products to electronic positioning," Wagner said.

The department put satellites in orbit to transmit positions and send timing signals to field receivers on the Earth's surface. The receivers calculate their distance from three to six satellites, Wagner explained. By calculating this distance, receivers show their exact position on the earth within 50 meters.

A technique called differential correction improves the accuracy, said Rick Day, assistant professor of soil science. By taking the coordinates of a known point on the earth and the less-accurate coordinates relayed by the GPS, one can correct for errors of other location signal points. The accuracy can be within a meter, Day said.

Some farmers have been using differential correction and GPS on their tractors for the last five years, Day said.

Farmers can have the soil on their land sampled and put into a database associated with the GPS unit on the tractor. As the farmer moves across the land, the computer screen shows where the tractor is in relation to the soil types, Day explained.

When the tractor gets to a soil type that requires less fertilizer, the computer signals the spreader to shut off temporarily. Precision agriculture allows the farmer to more accurately apply inputs to crops, Wagner said.

This practice may increase the potential yield of crops while decreasing the runoff from pesticides, fertilizers and other nutrients, he added.

Penn State has been researching agricultural uses of GPS for the past few years. Grid soil sampling, perimeter calculations and crop yields are currently being monitored with GPS on some research crops, said Scott Harkcom, farm supervisor for the Russell E. Larson Agricultural Research Center.

While the agronomy farm has the technology for precision agriculture, Harkcom said it is not in use because the research plots are so small. He said he believes within the next few years, Penn State will work more extensively with this technology.

Because of the same size and scale concerns affecting the research farm, this technology may not be economical for Pennsylvania's small farms.

Computer equipment and soil samples can be costly, Day said. Large farms in the Midwest are adopting precision agriculture practices more quickly than local farms.

"If it could be done where the farmers would break even while the impact on the environment is reduced," he said, "it's going to help out agriculture in the long run."

SOURCE: GPS: A Guide to the Next Utility by Jeff Hurn
GRAPHIC: Kara Heermans