Drop by Drop
Flying over parts of the American West, airline passengers look down on a pattern of green circles and stripes. A revolution in the way we irrigate crops may not be visible from 30,000 feet up, but on the ground Oregon growers and OSU scientists are developing new ways to grow crops using precise delivery of water and nutrients exactly when and where plants need them. These new technologies are dramatically reducing water use and runoff while increasing crop yields and quality.
The rhythmic pumping sound of a center pivot is the heartbeat of many successful farming operations in the Hermiston area and beyond. Recent advancements in center pivot irrigation make maximum use of a limited water supply, fully adjustable according to soil moisture levels. In order to research farming methods using the same state-of-the-art technology that the growers themselves are using, Hermiston-area growers and businesses have contributed five center pivot irrigation systems to OSU’s Hermiston Research and Extension Center.
“Their gift allows the Hermiston center to have the greatest research acreage under center pivot irrigation of any experiment station in the West, and possibly the U.S.”says Phil Hamm, the center’s superintendent and an Extension plant pathologist. The newest addition to the system controls how the pivots work and is fully programmable from a central computer.
“Some of the growers in our area have 200 or more center pivots, each irrigating a circle of 50 to 150 acres,” Hamm says. “New technology can program each pivot to deliver a precise amount of water, with timing and volume remotely controlled to deliver only what the crop absolutely needs. A controller can be in a central office, or anywhere in the world with Internet service, and can track each pivot, direct its speed and movement, and turn it on or off as needed.”
The best way to prevent nutrients from leaching to the groundwater is to apply only the amount of irrigation water needed by the plant and to spoon-feed just the right amount of nitrogen fertilizer to crops. New low-pressure technologies and precision nozzles allow that level of spoon-fed accuracy. Part of the research at the Hermiston center is examining how crops respond under deficit irrigation: further limiting water and nutrients and measuring the relationship between water stress and crop yield.
At the Malheur Experiment Station, OSU researchers are working with Ontario-area growers to produce high-quality potatoes and onions with less water. Clint Shock, the station superintendent, has spent much of his career researching methods to improve irrigation efficiency. Most recently, he and Erik Eldredge, a faculty research assistant in OSU’s Crop and Soil Science Department, are using soil moisture sensors to pinpoint exactly when and how much water to put on crops. Shock developed the calibration equations for these sensors that enabled the manufacturer to successfully market the instruments worldwide.
Shock and Eldredge have arrayed more than 300 temperature and soil moisture sensors among six differently irrigated plots. The information from the sensors helps the scientists calculate soil water tension, the force necessary for plants to pull water from the soil. The higher the tension, the drier the soil. The new technology can tell you if last night’s rain was enough to give your onions a good drink, or if today’s cloud cover slowed evaporation from the field, Shock says. Knowing precisely how much water to apply is vital for producing a high-yield crop and limiting evaporation, plant disease, erosion, and fertilizer-laden runoff. Many of the innovations developed at the Malheur Experiment Station in onion drip irrigation and potato irrigation management have been copied by researchers and growers in many areas, even overseas.
Jerry Erstrom is an example of a Malheur County grower who is putting irrigation innovations to work in his fields. Erstrom, chairman of the Lower Willow Creek Working Group, and his neighbors are working with several groups including the Malheur Watershed Council, Oregon Watershed Enhancement Board, the Bureau of Reclamation, and the local soil and water conservation district to retrofit the county’s open air canals and ditches with pipes and pressurized systems to improve water delivery and allow more controlled water use.
“How you irrigate depends on the crop you’re growing and the goals you want to achieve,” says Marshall English, an irrigation engineer in OSU’s Department of Biological and Ecological Engineering. English and OSU colleagues are developing an online advisory service to help growers create an irrigation management plan. Farm managers can enter information about their soils, crops, current irrigation system, and harvest goals into the Oregon Irrigation Scheduling On-line system. Then, during the growing season, the system automatically downloads weather data each day and uses the information to calculate irrigation schedules.
With the system, which is in its first year of online testing, growers can develop an irrigation strategy that, for example, in a water-short year will only partially irrigate one crop to save water for other crops.