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California conditions challenge overhead irrigation

California conditions challenge overhead irrigation

Irrigating with overhead sprinkler systems poses unique challenges in California. Mistakes often "self-inflicted wounds."    

At nine years old, Liam Taylor was easily the youngest member of a panel of growers who talked about the virtues and challenges of pivot irrigation systems for California crops during a field day at Five Points, Calif.

His dad, Will Taylor of King City, Calif., south of Salinas, saw to it that Liam was there to describe the ease of managing the system Taylor uses to grow potatoes that go to buyers, including In-N-Out Burger.

“It’s easy,” Liam affirmed when pressed by participants in the field day.

But not all is easy when it comes to overhead irrigation and use of conservation tillage and cover crops. Participants in the field day at the West Side Research and Extension Center got an earful about the challenges of those systems and the potential rewards for adopting them.

Jeff Mitchell, cropping systems specialist with the University of California’s Kearney Agricultural Center, described the experimental acreage as “the most visited field in California.” That’s because of what’s been going on there for 10 years: research into growing crops using conservation tillage and cover crops, and – more recently – overhead irrigation coupled with those two practices.

Among successes Mitchell cited was a crop of 52 tons per acre of processing tomatoes on land in conservation tillage.

Will Horwath, professor of soil biogeochemistry and soil biogeochemist at UC Davis, cited another positive development: Carbon was increased on the experimental plots “up to 5 tons per hectare,” about 2.5 acres, by combining reduced tillage with cover crops.

Each step, he said, combined to result in doubling of carbon content in 10 years.

A hands-on experiment later in the field day showed the importance of added carbon.

Volunteers did a soil infiltration test and collected handfuls of soil from plots in which a cover crop and conservation tillage was used and from sites where no cover crop and standard tillage was used.

Genett Carstensen, a soil conservationist with the Natural Resources Conservation Service, cited differences in slaking in the soil clumps after they were immersed in water. “Carbon acts as a glue,” she said, pointing out that the soil from the cover crop/conservation tillage plot remained bound together. By comparison, soil from the non-cover crop/conventional tillage plot crumbled quickly.

Mitchell talked of the use of overhead irrigation on crops that included wheat, corn, tomatoes, onions, cotton and broccoli. He said one of the characteristics of the overhead systems was “uniform water applications.” He emphasized that water evaporates from bare soil more quickly than from soil with cover crop residues. Moreover, he said, reducing tillage has been shown in studies in Nebraska to save nearly 1 inch of water in a growing season.

Learning curve

Mitchell conceded there has been a learning curve at the experimental fields in Five Points. He said it is important to understand and select proper water application rates, to avoid the temptation of irrigating “on the edge” of the crop’s true water needs and to strive for larger application volumes to account for what is lost through evaporation.

Joy Hollingsworth, a graduate student at Fresno State University, talked of tests done in fields comparing overhead irrigation with drip irrigation. She said chlorophyll levels were higher in plants watered with overhead compared to drip, soil under overhead was two degrees cooler throughout the season, there were significant higher number of weeds with overhead than drip, and mite flare-ups were notably higher in drip compared to overhead, at 37 mites per leaf in drip compared to one per leaf in overhead.

During one presentation, Ray Batten of Valmont Industries was asked why overhead sprinkler systems are so high above the ground. He explained that corn can reach as high as 16 feet tall, but he added that sprinklers can be dropped to the canopy of more low-lying crops such as processing tomatoes.

Five Points grower John Diener, who has a dozen overhead pivot systems, said he encountered some difficulties with a variety of corn that grew so tall it stopped the pivot from moving overhead.

Diener was part of the panel of growers who discussed the challenges and rewards of overhead systems. He said the pivots greatly reduced labor and helped in getting away from moving aluminum pipe.”

Diener said some varieties are better suited to overhead irrigation, and he said he has taken steps to avoid the pivots getting stuck: “We use wood chips from almond prunings in the furrow where the tires run.”

Will Taylor, the King City grower, said his pivot systems – seven of them – work well on what he called “tough ground, Pismo Beach without the beach” and rolling hills.

“We have a better ability to distribute water and limited run-off,” he said.

Taylor said he has managed to produce potatoes that are 2.5 to 4 pounds in size and highly prized by In-N-Out Burger, often putting water less than 1 foot into the ground with the overhead system.

Manpower savings

Darrell Cordova, who farms in rolling hills near Denair, Calif., said the pivot system he uses has taken the place of a crew of three men who had spent three hours twice daily moving pipe to irrigate.

“Now I go out and push a button,” he said, adding that his pivot works on clay, sandy and sandy loam soil and can be programmed to do chemigation and fertilization, including spraying for weeds on Roundup Ready corn.

Cordova said he changed the spray nozzles to better suit his crops, and that the overhead system “washes your mites off.”

Scott Schmidt, a neighbor of Diener’s explained that he traveled with him a few years ago to Washington state to check out systems there.

He said most setbacks in applying the system in California, for him, have been “self-inflicted wounds” as he learned infiltration rates and how plants were responding.

Schmidt has seven pivots he can operate remotely from a cell phone. He gets text messages when a system starts or stops. The field day concluded as darkness fell and Schmidt showed one of his pivots at work over a field of Pima cotton not far from the Five Points research center.

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