Making the Most of Every Drop: Research and Technology for Smarter Irrigation

variable rate smarter irrigation

Last year will be remembered by a lot of growers as a time when more water came from below their feet than above their heads. It was an El Niño year, which always promises extreme and erratic weather patterns – and 2016 did not disappoint.

According to USDA data, drought touched almost 1,000 counties across the country in 2016. The entire states of California, Nevada, New Jersey, Connecticut, and Alabama fell under drought. And the majority lands of Oregon, Hawaii, Montana, Wyoming, Mississippi, Tennessee, Georgia, New York, Pennsylvania, and all of New England went dry.

Some interesting quick takeaways from 2016: California farmers took losses but they did better than in some previous years of its ongoing drought. And many states in the Southeast showed their vulnerability when the regular summer rains stop showing up. This all serves as a reminder that water is a finite resource, and security in farming means being careful with every single drop.

A recent report on the economic impacts of the 2016 drought, released by the Center for Watershed Sciences of the University of California, Davis, found that agriculture remains strong in the state even though this was its fourth straight dry season. Irrigation has always been a critical issue in the state, and now California’s complex piping and water distribution system has many farming districts at odds over who should get how much water from a dwindling reservoir system. Pumping groundwater for irrigation has helped fill the void.

California has been a leader in the use of subsurface drip irrigation for decades now. Water is valued here probably more than anywhere else in the country. To put the state’s growers’ intense need for water into perspective: If using only irrigated water, it takes .75 gallons to produce a single pistachio, 3.3 gallons for a tomato, 1.1 gallons for an almond, and 4.9 gallons of water for one walnut. California grows 90 percent of each of those crops for the entire U.S. market. The state’s exclusivity in these (and many other crops in which it holds the national majority stake) is its economic strength, but water supply is its vulnerability.

“When the spillover effects to other sectors of the economy are considered, we estimate total output value losses of $600 million and 4,700 full and part time jobs statewide due to drought in agriculture,” the U.C. Davis report states. “Despite the drought, overall agricultural value and employment grew statewide during recent drought years due to several factors including favorable global prices for some crops.”

The loss equates to more than 1 percent of the state’s annual agricultural output. Still, with four years of drawdown in reservoirs and groundwater for irrigation, a possible fifth year of drought could prove problematic, the report states.

With rainfall down in so many places, research agencies are testing how crop returns look under varying levels of irrigation. For instance, in the Texas panhandle, the Natural Resources Conservation Service (NRCS) hosted the 3,4,5 Project. It was a trial/demonstration to see how corn crops fared if they were irrigated at 3, 4, or 5 gallons per hour from a center-pivot irrigation system with supplemental rain.

The project was aimed at seeing if farmers in the Ogallala Aquifer could still turn a respectable profit while drawing less water. The Ogallala is the nation’s largest aquifer, but it is also being pumped at an unsustainable rate.

At the end of the season, the corn was harvested and costs were tallied. The 3-gallons-per-minute field netted $463 per acre, the 4-gallons-per-hour field netted $483 per acre, and the 5-gallons-per-acre field netted $513. So yes, more water equals more money per acre. But by those numbers, it required 66 percent more water to increase the return by just 11 percent. The demonstration also showed some other results.

“It’s interesting to know that the crops with less water, applied at 3 gallons per minute per acre, had the deepest root systems,” said Mike Caldwell, NRCS resource team leader in Dumas, Texas, in an NRCS blog post. “This shows that the crop’s roots were using water in the entire soil profile with no water waste. It’s important to know this at a time when water levels are continuing to decline.”

drought monitor map sept 2016

A U.S. Drought Monitor drought assessment map. In 2016, areas already hard hit – like California – continued to face drought conditions, and other areas of the country that typically experience relatively reliable rainfall saw deficits. Agricultural producers are looking to more precise irrigation methods to help deal with the scarcity of water. Credit: The U.S. Drought Monitor is jointly produced by the National Drought Mitigation Center at the University of Nebraska-Lincoln, the United States Department of Agriculture, and the National Oceanic and Atmospheric Administration. Map courtesy of NDMC-UNL.

Drought also struck hard in the Southeast. The region usually enjoys reliable rainfall across the calendar. For instance, Georgia averages about 3.3 to 5.3 inches of rainfall per month throughout the year. In 2016, most parts of the state saw deficits of at least 25 percent in annual rainfall. In Alabama, the governor held a November press conference on the barren bed of Lake Purdy, the city of Birmingham’s reservoir. The lake had reached its lowest level in decades. And farther south, Florida finally started getting litigious with Georgia as decreased flows from the Flint and Chattahoochee rivers have hurt salinity levels in coastal estuaries and affected oyster populations.

This new Southern outbreak of the water wars has been decades in the making, but the growing problem actually had a role in helping to further regional research on smart irrigation. The lower Flint River Basin hosts about 8,900 center-pivot irrigation systems to irrigate peanut and cotton crops. They draw from a shallow aquifer, which has had a dramatic effect on local waterways. In past years, some tributaries to the Flint would run dry if there wasn’t enough rain. A multiagency partnership formed to study and try to curb water usage. The University of Georgia set up a research program in the area, and soon practical solutions, like dropping nozzles on center-pivot systems to minimize evaporation loss, were being rolled out to local farms.

The water disputes also led to some of the early testing and development of new smart variable rate irrigation technology. In 2004, the University of Georgia released its first stab at the technology to be tested in other areas.

Today, Neil Douglas, market manager for Trimble’s Irrigate IQ suite of products, says that a good number of the company’s U.S. customers are located in the Southeast. The technology that conservationists hoped would keep more water underground and in rivers, it turns out, is being adopted by farmers who want better harvests and lower operating costs.

When it comes to irrigating your fields, variable rate technology “is the difference between a paint roller and an inkjet printer,” said Douglas. With each nozzle head controlled separately, farmers can put exactly as much water as they need precisely where it belongs. They can also completely shut off water as the pivot passes over field infrastructure like access roads or ponds.

The way these systems work is that the nozzles don’t actually adjust the water pressure. Rather they open and close at varying rates, like the fuel injectors on a car’s engine, to deliver the right amount of water. In areas that need to be wetter, the nozzles stay open longer – and vice versa. With the proper prescription programmed into the controller, the irrigation system accounts for areas of a field that are naturally drier or wetter and applies just the correct amount of water.

This technology is improving previously tricky corner-arm irrigation. As a center-pivot swings its corner arm outward to increase the amount of field being irrigated, it would typically drop an uneven amount of water throughout the zone. Trimble’s Uniform Corner system offers a variable rate irrigation package that adjusts the center pivot’s movement and delivery to the corner arm. Douglas describes a center-pivot system operating a 100 percent flow throughout its normal rotation. But when its arm begins to swing, the center pivot knows to slow down so that it can divert water to the extension arm. By moving slowly, the center section will still achieve the desired saturation even though the flow rate has dropped. Meanwhile, the smart nozzles over the corner are applying the same amount of water there, too.

Farmers can control the variable rate systems remotely, eliminating the need to handle each pump manually. They can monitor and control dozens of fields without leaving their house, though one limiting factor, Douglas noted, is cellular service; Irrigate IQ products need a cellular data connection to communicate, so some farms are still just too remote.

Variable rate irrigation equipment is added to existing center pivots, so the expense is fairly reasonable. A few studies have shown that a system can usually cost anywhere from about $15,000 to more than $30,000 per center pivot, with much of the price potentially being offset by state and federal grants. After that, users can expect to see anywhere from 7 percent to about 25 percent water savings.

Beyond the water savings, Douglas also noted that some of his customers are reporting other benefits. Potato farmers in Idaho that have switched to variable rate irrigation mentioned that they are seeing their products last longer in storage. The theory, anecdotal as it is, is that potatoes watered precisely may have better moisture levels and therefore don’t spoil as quickly.

Whatever the reason, meteorologists are suggesting that future weather patterns may be less even and unpredictable. And many farmers pumping groundwater are seeing the water levels under their feet continue to decline. If we are going to keep our water systems viable for production, we must make smarter use of the resource. Luckily, the technology exists to accomplish that. The question is how soon farmers will come around to adopting it in numbers large enough to make a difference.

Caption for top photo: Technician Luke Britten (left) and agricultural engineer Susan O’Shaughnessy (right) adjust wireless infrared thermometers while technician Brice Ruthardt (center) uses a neutron gauge to measure soil water content in a field in Bushland, Texas, which features a variable rate center-pivot irrigation system that can deliver exactly the right amount of water precisely where it should go. Scientists use high-resolution data such as those collected in this field to optimize crop performance in specific environmental conditions. Credit: USDA photo

This article was originally published in the 2017 edition of U.S. Agriculture Outlook.

Leave a Comment

  • (will not be published)