By Dennis Pollock
It has become a well-worn cliché in the world of irrigation: “If you want to manage water, you have to measure water.”
Bill Green knows the expression well, as both an agriculture specialist at the Center for Irrigation Technology at California State University, Fresno, and as a grower of raisin grapes in nearby Fowler.
At Fresno State’s Ag Tech Day last month, Green said, “As a farmer, I want to be as efficient as possible, but I can only do that if I know how much I pump.”
Measurement of water use was a centerpiece of the ag tech day, sponsored by the Center for Irrigation Technology. The topic came up in virtually every presentation at three different campus sites. It’s taking on even more importance as California’s Sustainable Groundwater Management Act now calls for measurement of water use.
CIT consultant Sarge Green said managing groundwater is a challenge facing growers far beyond just drought-parched California.
He pointed out that groundwater conflicts are a national issue, one that came before the U.S. Supreme Court over a water clash between Mississippi and Tennessee. It’s also been a big topic in New Jersey, Kansas and elsewhere.
A field day participant asked Sarge Green if he thinks collecting water-use information makes sense from an economic standpoint.
He simply argued for its usefulness, saying, “When it comes to energy use, crop productivity and distribution, meters give those three different data sheets.”
Steve Huth, co-owner of TechnoFlo Systems in Porterville, said the cost of meters is “cheap for the amount of data that can be used to better manage the system.”
Huth was among those who said installation of measurement devices is pivotal.
“Without proper installation, the amount used can be plus or minus 2 percent, and that can add up over time,” Huth said. “It’s like estimating the speed of your car without a speedometer.”
Mallika Nocco, assistant specialist with the University of California Cooperative Extension for soil-plant-water relations, said return on investment in metering depends on “how you integrate what you gather and make decisions.”
Alex Breckenridge, senior agronomist with GroGuru, put it this way: “Moisture probes are not a magic wand. It’s like a treadmill in the basement. If you expect to lose weight, you have to use it.”
Both Nocco and Breckenridge talked of various ways to collect data to arrive at information on field capacity, plant stress level and crop coefficients for water needs.
That can involve canopy-based optical sensing, high-resolution soil maps and use of drones, airplanes and satellites.
Breckenridge touted Sentek probes and described how his company translates Sentek data “into something actionable.” The sensors, he said, can be used to manage water “365 days a year.”
A Sentek representative said soil moisture probes need to match the root depth of the crop, for example, 5 feet in walnuts, 3 feet in corn.
“You don’t want water to go past the root zone,” he said. “It’s a waste of water, fertilizer and energy.”
At one field site, workshop participants heard about a groundwater research project on campus looking at a way farmers might implement recharge systems within their fields that do not impact their farming operation.
The recharge system is installed below the crop’s root zone. It’s composed of a continuous 4-inch pipe system with perforations, and any runoff water or excess available surface water can be transported and distributed through this pipe. That facilitates the percolation of water into the groundwater aquifer.
By installing this system below the crop’s root zone, any amendments such as fertilizer and pesticides will not be transported into the aquifer. Because it is fed underground, use of the water does not disturb farming operations aboveground.
It won’t result in standing water that would impair spraying, for instance.
Cordie Qualle, a professor in civil engineering at Fresno State, talked of the recharge research project as he stood beside the Helm canal from which water is being pulled. He said it is a way to “marry up access to surface water and farmland without disturbing farming operations.”
It’s easiest to do if trenching is done before crops are in place, he said.
Water is filtered before it goes into a pipe that is fed into a gravel envelope.
The cost to do it is not cheap. Qualle said it amounts to $4,000 an acre to install the system.
Greg Allen with REDtrac in Bakersfield was among those who worked with Qualle to put the system in place. He said a Sentek moisture probe extends about 40 feet into the ground.
Allen said the cost for probes has been dropping. He lifted a 1.5 meter probe that once sold for $2,000 and said it now sells for two-thirds of that price.
He then quipped about farmers’ penchant for using cellphones to access their water data remotely.
“We say that farmers want to run 10,000 acres on a 10-square-inch cellphone,” Allen said. “You can almost do it.”
