By June 15 gasoline-powered augers will have drilled 100 holes in the corn, cotton and peanut fields of the Lower Flint River Basin in southwest Georgia. Into the holes, scientists from the University of Georgia (U.G.A.) will slip half-meter-long PVC pipes filled with sensors for soil moisture and temperature topped with a flexible antenna that can be run over by a tractor and spring back into place. Over the course of the next two years, these sensors will continuously relay soil conditions from 20, 40 and 60 centimeters deep to a computer. Combined with more accurate weather forecasts, the data will help farmers decide where and when to use their irrigation systems.
"The biggest problem we've got with irrigation is we just don't know—we use old wives' tales to decide when to irrigate," says farmer Marty Tabb, who will host the probes in a field at his 1,050-hectare Bushwater Farm near Colquitt, Ga., to help him irrigate corn, cotton and peanut crops. In addition to saving water (agriculture is responsible for 70 percent of human water use globally), the technology can also help produce more crop per drop. "Using the simplest soil monitor and a computer program, my peanut yields jumped 20 percent," Tabb reports. "I know, just from that, that if we learn how to water corn, cotton, wheat, we can save water because we tend to overwater."
Overwatering is a major problem in the Lower Flint River Basin, which lies in a region that has been gripped by drought so severe in recent years that it prompted the former governor of Georgia to pray for rain. The region produces the most peanuts and pecans in the nation, as well as vast quantities of cotton and sweet corn. And the Lower Flint River Basin is the major recharge zone for the Floridan Aquifer that supplies water to Florida, Mississippi, Alabama, Florida, South Carolina and Georgia, as well as the home of several endangered freshwater species, such as the flatwoods salamander and the oval pigtoe mussel.
Farmers in the Flint River Basin have a direct impact on this groundwater resource, because waters on the surface and belowground are directly linked: a hurricane's downpour in the area can replenish the aquifer, whereas too much pumping of underground water to irrigate fields can literally suck the water out of surface rivers and streams. "Because of the drought and because of us irrigating, we have pulled water down, and the springs along Spring Creek don't pump anymore," Tabb says of the Flint River tributary in his backyard. "You couldn't have told me that creek would ever dry, but I drove my motorcycle two miles down Spring Creek because it was so dry."
In a bid to cut down on that water use—while maintaining the more than $2 billion worth of corn, cotton, peanut and other crop production in the region—the Nature Conservancy and the U.S. Department of Agriculture, along with U.G.A. and the University of Florida, teamed with more than 1,000 local farmers starting in 2000. The partnership started by switching some irrigation systems from high pressure mists to a low pressure system that more directly mimicked rain, saving water and energy. When applying at high pressure "you lose water to wind drift and also evaporation," explains David Reckford, director of this Flint River Basin Partnership for the Conservancy. The switch to a low pressure system alone can reduce water use by more than 22 percent.
The farmers in the region employ center-pivot irrigation systems, which pump water from underground and spray it on crops in a circular pattern from rolling metal tubes fed from a central pivot. The water conservation partnership focused on this technology specifically. Next, they helped some local farmers install, demonstrate and prove so-called variable-rate irrigation, which instead of simply dumping water on a given field equally at every point can vary the application from place to place. "Last year that system at my farm, we saved two [million] to three million gallons [7.5 million to 11.3 million liters] of water by having that system cut off over wasteland," Tabb notes. "Do that over 500 systems and see how much water we can save."
Variable-rate irrigation systems save 15 percent of water use on average, the equivalent of roughly two irrigations a year. As a result, the technology has begun to spread to other farms in Georgia and nine other states, and it is now being offered as an option for new center-pivot irrigation systems worldwide. "As the price comes down, [variable-rate irrigation] is going to be common. Why water places that you don't need to water?" Reckford asks. "There are roughly 250,000 center pivots in the world so there are a lot of systems where that improvement could occur."
But variable-rate irrigation currently relies on a static map of a given field, water here but not there in an unvarying pattern and with little consideration of soil type or field condition. That's where the University of Georgia's new sensor probes, which allow farmers to monitor soil moisture in real time, come in. "The shape of the [field] map is changing as plant conditions change," explains U.G.A. agricultural engineer George Vellidis, who designed the monitoring system.
And, instead of farmers having to visit each field and check the data, the probes will relay the information to their home computers, where IBM's Cognos software will sift the data to find the relevant bits and determine where and when to water. "By managing every drop of water within the Flint River Basin, you're better meeting the needs of people and the environment," says Mark Werbeck, the IBM account executive for the project.
The project will spend $1.1 million on probes and software for 10 fields to test their efficacy over the next two years—one of the first applications of sensor technology and data management to agriculture. In the future sensors to measure nutrients or soil acidity could also be added to the probes, and Cognos software could integrate global positioning system data from tractors and fuel usage, along with the type and amount of seed applied. Regardless, the water data alone should cut down on farmer costs: even without the soil probes, the partnership's variable-rate irrigation and other technologies can already save as much as 57 billion liters of water per year. "Dumping water on the crop is the most expensive thing we do," Tabb says. "Water isn't free, given the price of electricity, oil and the equipment itself."
The new technology won't just help farmers in the 265,000-hectare Lower Flint River Basin, it will also help all those who rely on the water from the Floridian Aquifer—from the human residents of Savannah and Orlando to the alligator snapping turtle that inhabits the region's slow-moving rivers, lakes and bayous. The Lower Flint River Basin is home to the largest concentration of amphibian and reptile species in the entire U.S., many of which are rare, threatened or endangered. When farmers like Tabb conserve water, more of it flows within the region’s waterways. "There is a very strong ethic of conservation built deep into these men," Reckford notes. "They grew up on these rivers and streams. They love them. Having the tools to preserve them is something they support and are willing to take a risk to adopt."