By Brad Haire
University of Georgia

RFID is a system that can wirelessly retrieve information from RFID tags, small devices that contain silicon chips with antennas, said Vellidis, an engineer with the University of Georgia College of Agricultural and Environmental Sciences.

The idea of using RFID came up several years ago in a meeting among engineers in Georgia. Vellidis figured it could be the key to a system farmers can use to precisely schedule irrigation.

But he and research engineer Mike Tucker could find no published research on using it for irrigation. So they decided to develop a prototype system that uses RFID tags to wirelessly transmit soil moisture data from a field to a central location.

"We wanted to make something workable, wireless, low-maintenance and relatively cheap," Vellidis said, "and something that could relay information in real time."

Knowing the real-time soil condition in his field can improve a farmer's yields, he said, by giving his crops water when and where they need it. This improves his bottom line and can save water, too.

Research shows that cotton plants can lose as much as 200 to 300 pounds of cotton per acre if they become water stressed. The harm can be done before the plants show any signs of damage.

But sometimes the price of knowing may outweigh the benefit, he said. Commercial irrigation-scheduling systems use nodes with sensors in the soil throughout a field. The sensors collect data like soil temperature and moisture. A farmer can manually check each sensor or have the data sent to a central place. The latter is more helpful.

But commercial wireless systems can cost $700 or more per node, Vellidis said. Solar panels are often needed to supply the power. And systems with wires or cables can get in the way of farm work.

Georgia farm fields can vary in soil type. Each soil type holds water differently. To know precisely when and where to water, farmers need many nodes throughout a field.

The more nodes in a field, the more precise a system would be. About 20 per 80 acres, Vellidis said, would be ideal.

With RFID, one node in the UGA system costs about $70. That includes two soil-moisture sensors and two thermocouples for soil temperatures. A 9-volt battery, he said, would supply enough power for one season for a watertight circuit board the size of a playing card.

The circuit board reads the sensors' data and writes it to an active RFID tag, made by WhereNet Corporation. The RFID tag has a flexible antenna a tractor can easily pass over.

A central receiver could wirelessly retrieve the data. The farmer can use the data to decide when and how much to water.

The system, still in the research mode, isn't commercially available. But the projected cost for a 20-node system for an 80- acre field is about $2,700, Vellidis said, or about $35 per acre.

The research was funded by Cotton Incorporated and the Georgia Peanut Commission, Georgia Cotton Commission and Georgia Research Alliance.

Vellidis hopes the system can become commercially available through a startup agribusiness. Another product developed on the UGA Tifton, Ga., campus, called variable-rate irrigation, can now be bought through a startup company in Ashburn, Ga.

This isn't the first agricultural use of RFID. Canada uses it to identify cattle. It can trace a beef carcass at a packing plant back to its herd of origin. The U.S. Department of Agriculture is developing its own tracking system using RFID.