Growing Magazine - July, 2012

IRRIGATION MANAGEMENT

Technology and Experience Combine for Irrigation Efficiency

By Nancy Riggs

Though tree nuts, leafy greens, chiles and grapes produced on arid lands in the Southwest all have different irrigation needs, specialists and growers alike agree on two points: Water is the most valuable resource, and irrigation efficiency is essential. Irrigation system performance, uniformity of water application and the response of the crop to irrigation are all interrelated measurements of how efficiently water is being delivered to the crop. Extension advisers, researchers and other specialists, along with growers, are focusing on ways to evaluate and improve irrigation efficiency, contributing to both profit margins and water conservation. Coupling growing experience and agronomic knowledge with emerging technology is giving growers the tools they need to help assure that they are applying their irrigation in the most efficient way.


Interns measure flows from a solid set rotator sprinkler system in a young walnut orchard, Red Bluff, Calif.
PHOTO COURTESY OF KEVIN GREER.

Help with efficiency

Mobile irrigation lab teams have existed in California for about three decades, assisting growers in evaluating irrigation efficiency. Initially organized by the University of California Cooperative Extension, a mobile irrigation lab in Tehama County is now sponsored by the Tehama County Resource Conversation District.

Kevin Greer is mobile irrigation lab manager in Tehama County, in the northern part of the Salinas Valley, where the primary crops are almonds, walnuts, prunes, and table and oil olives. Greer and irrigation technicians take measurements in irrigation systems including the level of pressure, range of pressure, diameter of the main and of submains if they exist.

Greer said, "We look at pressure at pumping, in the middle and at the end of the line to determine the pressure, and if we are losing pressure along the lines from clogging, leaks or other issues. Next we check the flow by catching it in a beaker or cup and measuring the amount that flows in a specific amount of time."

Following the collection of data, the irrigation team uses a Cal Poly program to determine the system's efficiency, or distribution uniformity (DU). A comprehensive report is prepared, and specialists make recommendations to the grower that can result in more efficient operation, resulting in savings in both energy costs and water.

At the southern end of the Salinas Valley, in an area known as the Salad Bowl for its vast fields of leafy green crops, Michael Cahn, UC Monterey County Extension farm adviser, works with growers on irrigation efficiency issues. Cahn said, "We offer educational seminars, and we evaluate irrigation design, showing growers issues on a map so we can suggest changes to improve efficiency." Cahn emphasized the management of the irrigation system as a major contributing factor in efficiency, and help is provided to growers on how well their irrigation system is operating. A season-long evaluation looks at scheduling flows and soil moisture, and large-scale studies of irrigation management in lettuce fields help growers identify irrigation efficiency strategies.

While a number of crops have published coefficients, Cahn and associates used infrared techniques to photograph canopies for leafy green crops that do not have established coefficients. The photographed canopies were evaluated to help establish coefficients that aid growers with irrigation decisions.

"Leafy greens are so sensitive to moisture, and prolonged deficits hurt yields," Cahn said. He noted the importance of training people in different agencies to work with irrigation efficiency evaluations.

Combining experience and technology in vineyards

Paolo D'Andrea manages New Mexico Vineyards in Deming, N.M. The 300-acre vineyard, established in the mid-1980s, is New Mexico's largest vineyard and sells grapes to wineries in Texas, New Mexico, Arizona and California. D'Andrea is owner of the adjacent Luna Rossa Winery (www.lunarossawinery.com), a 28-acre vineyard and winery established in 2002. D'Andrea, a fourth-generation grape grower and native of northern Italy, has managed New Mexico Vineyards since shortly after its establishment.

New Mexico Vineyards has aboveground drip irrigation that was installed when the vineyard was established. D'Andrea said, "I decided to try subsurface in the new vineyard. The drip tape has been in use since it was established." Proper maintenance of irrigation systems is essential, and D'Andrea noted the importance of filtration to avoid clogging in the lines.

Bernd Maier, New Mexico State University viticulturist, works extensively with growers in the state and has established weather stations at New Mexico Vineyards, Luna Rossa Winery and other sites. Maier said, "We are trying to help growers maximize use of available water for highest quality and quantity in yields. Water is our most valuable resource, and the system is managed considering this constraint."


Aboveground irrigation in a research vineyard at Fabian Garcia Science Center, New Mexico State University.
PHOTO COURTESY OF BERND MAIER, NMSU.

Maier emphasized the importance of ET understanding, and that once the ET is determined, the amount of water available must be determined so the vineyard can be designed. He said, "We sit down with the grower to determine the resources, field layout, varieties of grapes, available water on a per minute basis and soil types. In southern New Mexico, we have mostly level fields, so topography is usually secondary. We like to build blocks according to soil types and varieties. In micro-irrigation, the frequency is high. This allows us to always have the right moisture conditions for the plant and also mitigates some adverse soil conditions."

Weather stations, evapotranspiration (ET) charts and soil moisture probes all complement the experience developed about crop irrigation through the long growing history. "We usually install the soil moisture probes under the row between two plants," Maier said. "If there is one probe, it is located about 8 inches deep, and if there is a second one it might be around 24 inches deep. We use a lot of Decagon and Watermark probes in our research."

Soil moisture data at New Mexico Vineyards and Luna Rossa Winery is recorded on the station, and D'Andrea can read the data on a screen in the tasting room. Data is also sent via the Internet to a computer at New Mexico State University. D'Andrea uses the data provided, along with established plant coefficients, to complement his experience in making irrigation decisions.

"We currently are reworking the website where the public can view the data for the six viticulture stations in the state," Maier said. "The new website will have hourly updates and a data archive. Growers from around the state can use this information to extrapolate the irrigation needs for their own vineyards."

Managing disease and conserving water

Ed Curry, owner of Curry Seed & Chile, Inc., Pearce, Ariz., (http://curryseedandchile.com) has a diverse farming operation in southern Arizona that includes chile seed production. Curry has been on the leading edge of genetic development in stabilizing the heat in chiles, an essential element in the expansion of the commercial chile industry.

Efficient irrigation management is the lifeblood of his operation, and while no crop is possible without irrigation, Curry limits that irrigation in the deeper soil profile. "I try to leave the deeper profile drier to manage disease during our monsoon season," he explained. "It's a fine line." Southern Arizona receives little rain, and most of it comes in heavy summer storms known as monsoons.

Curry is in his fourth season of using EasyAG moisture probes, manufactured by Sentek Technologies and distributed by Fenn Ag Co., Cochise, Ariz. Curry's probes are placed as close to the rootzone as possible, under the center pivot, with one probe per chile block. Soil moisture data is sent to an FTP site maintained by Steve Fenn of Fenn Ag Co. Fenn generates weekly reports for Curry.

"The probe is another tool for us to use," Curry said. "It helps us monitor our soil moisture in the most efficient way to manage disease in the chiles. It also helps us monitor the amount of water needed. We don't want to put on more than is needed for the crop, which costs us extra." Curry cited the importance of saving water as a production cost factor and added, "We're starting to use dribblers with our center pivot irrigation. It's the most effective way to irrigate, with less water lost than with sprinklers."

While irrigation specialists and manufacturers continue to explore new avenues to make technology increasingly more accessible, growers are reaping the benefits of the technology that's currently available, focusing their efforts on the quality and quantity of their yields. Irrigation efficiency is a major tool in addressing these essential elements of crop production. This efficiency is increasingly being refined by combining growers' experience with research and emerging technology.

Nancy Riggs is a freelance writer and frequent contributor. She resides in Mount Zion, Ill.