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.