Where The Water Goes

By Boyd Kidwell
Progressive Farmer Contributor

Without irrigation water, farming is impossible in ‌Madera County, California. That’s where Tom ‌Rogers farms.

‌Tom and his brother Dan farm land that’s been in the Rogers family for 100 years. Their father planted almond trees on the farm in 1981, and the Rogers brothers grow 175 acres of almonds in Madera, in the eastern San Joaquin Valley.

Rainfall is stingy--and untimely. This arid to semiarid region receives an average of 10 to 12 inches of rainfall a year but often not when their crop needs moisture the most, Rogers explains.

To that end, the Rogers family is firmly engaged in smart water management. Tom’s father installed a soil aerometer (moisture probe) in the 1980s to help him make irrigation timing decisions. He was ahead of his time.

Traditionally, and even up until recently, most almond growers irrigated “on the calendar,” a process that filled the soil profile with water no matter if it was timely. After all, surface water was available, and pumping costs were reasonable.

Those days are gone. The family’s irrigation canals, once full of water supplied by their irrigation district, have been nearly dry in recent years. All of Rogers’ irrigation water was supplied from an underground aquifer. And, that water is getting expensive.

In 2016, Rogers paid $120 per acre-foot for water from his water district. Some farmers in other water districts were paying $2,000 per acre-foot, he says. Still, Rogers is saving no money by pumping water. Water pumped from his wells also costs approximately $120 per acre-foot.

Water To Need. “It’s imperative to know where your water is [in the soil profile] if you are using it for the crop or flushing water through the system. If so, you are also losing nutrients,” Rogers says. “We can water according to a calendar or according to the trees’ needs. Our goal is to water according to the crop’s needs.”

In 2014, Rogers won the California Farm Water Stewards Award for his smart water management. The award is given by the Pacific Institute, Community Alliance with Family Farmers and the Ag Innovations Network.

“We’re learning more about irrigation all of the time. For us, this is an exciting time,” the California nut grower says. For example, Rogers has transitioned his system from microsprinklers to double-line drip irrigation. That reduced water usage by 25%.

The Rogers’ ranch is divided into nine irrigation sets, one set per water well. The soil moisture probes are set at 6 inches, 10 inches, 14 inches and 18 inches. He also monitors moisture at the 36-inch depth to make sure water isn’t moving through the soil profile.

New to the Rogers’ operation is a system using computer-automated valves. The irrigation software program sold by WiseConn USA, Clovis, California, releases water through his drip lines in brief pulses. In that way, the moisture moves laterally through the soil and root zones of the trees, instead of down through the soil profile.

The Root Zone. It has taken time for Rogers to learn the ins and outs of the new irrigation system. But, he has found success. One of his discoveries is that the depth from surface to 18 inches is the key zone for producing almonds. “For almond trees, the top 18 inches of soil has 80% of the root activity,” he explains. A 45-minute pulse of water provides optimum results in that foot and a half of soil.

“When you run irrigation water for a long time in one place, you’re going to pool water on the surface, and pooled water evaporates,” Rogers says. “We try to match our irrigation to the infiltration rate of the ground. Some ground allows water to flow freely into the soil, and with other ground, it takes longer for water to soak in.”

Weather stations are critical to Rogers’ irrigation system. They are installed at three locations around the ranch and provide temperature, humidity, wind speed and rainfall information. Rogers monitors weather conditions and tracks the evapotranspiration rate to assess how his trees are using available water.

The soil moisture probes cost $2,500 to $3,000 each, and the weather stations cost $1,500 each. But, the investment produces returns.

The new technology has paid off with almond yields that average 300 to 500 pounds per acre above the state average. This is a gain of $690 to $1,150 per acre. Rogers credits better water and nutrient utilization for increased yields.

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