By Brad Haire
University of Georgia

Crops have to have water from rain or irrigation to grow properly. The center pivot is commonly used for irrigation in Georgia.

But farmers don't have much control over how much water the irrigation nozzles spray as they pass over crops like peanuts, cotton or corn. And even small fields can vary widely in topography and soil types. Some places can be wetter or drier than other places in the same field.

Variable-rate irrigation takes all of this into consideration, says Calvin Perry, an agricultural engineer with the UGA College of Agricultural and Environmental Sciences.

The VRI concept is simple: Apply water when and where crops need it. Don't apply it where they don't. VRI technology uses computer maps, sensors and software to control where and how much water the nozzles on a center pivot spray on crops.

Researchers with the UGA National Environmentally Sound Production Agriculture Laboratory in Tifton started developing VRI in the late 1990s.

UGA scientists have tested the water efficiency of VRI on farms in Georgia. The systems allowed the farmers to place the right amount of water on their crops for the best yields and reduce the water used by 8 percent to 20 percent in each year.

Using a $500,000 Natural Resource Conservation Service grant, Perry and other CAES specialists are now sharing the technology's potential with researchers and farmers in other states.

In cooperation with Clemson University, VRI systems are now studied in South Carolina and being demonstrated to farmers there.

This spring, in cooperation with the University of Arkansas, the technology was installed in Poinsett County, Ark., on a 4,000-acre plantation. It's part of the Judd Hill Foundation, established in 1985 to foster research and public outreach on progressive techniques in farming.

"Researchers there are working on their own pivot irrigation studies and thought VRI would be a good complement to it," Perry said. "Agricultural water use is a big issue in Arkansas just like in Georgia."

The VRI system received much attention during the plantation's annual field day Aug. 31, Perry said.

"This opportunity in Arkansas will allow us to see how the VRI product does under other climate conditions and other soil conditions, particularly how it does in the cotton-growing Arkansas Delta region," Perry said.