Moisture Misers

June 19, 2018 11:32 AM
Moisture Sensors - Chris Henry

Which technology is left on the table by many farmers, yet saves dollars on fuel, labor, wear-and-tear, pickup mileage, time and thousands of gallons of water? The open secret of soil moisture sensors.

Chris Henry, associate professor and water management engineer at the University of Arkansas (UA) Rice Research and Extension Center in Stuttgart, is a precision irrigation apostle. His message is catching the ear, and pocketbook, of producers. “How many dollars does a planter population monitor make for a grower,” Henry asks. “That answer is hard to quantify, but try to find someone who has had a planter population monitor and traded it off for one without. The exact same principle applies to soil moisture sensors.”

For growers interested in irrigation automation and a reduction in uncertainty, Henry recommends starting simple: “There’s a range of sensors, but start with something that makes sure you’re using the right amount of water and meeting crop demand.”

Four Watermark sensors (placed at 6", 12", 18" and 30" depths) cost roughly $150, along with a manual reader for $250. Placed into a free smartphone app designed by Henry (Soil Sensor Calculator), the sensor data is entered and converted to how much water is available according to soil type. Once calculated, irrigation predictions are simplified. “For example, it (the app) reports you have 1" of plant-available water, so at a ¼" per day of crop water demand, we need to be finished irrigating the field in four days. It’s that simple,” Henry says.

When a pivot makes a 40-hour turn and drinks 4 gal. of diesel per hour ($2.50 per gallon), the cost for a single revolution is a painful $400. “Moisture sensors tell you exactly how much water is in the profile. In the right circumstances, they can save a [pivot] turn in a single week,” he notes. “Even more, let’s say you save three irrigations. That’s all without NRCS help, but sign up for an Irrigation Water Management Plan in the fall and they’ll pay 50% to 80% of costs.”

Greg Simpson, irrigation program associate with the UA Division of Agriculture, echoes Henry’s take on sensor-driven irrigation. “You get more efficient the second you start using sensors because of time, labor and money,” he says.

Tommy Young runs 21 pivots in Jackson County, Ark. He says they have transformed his operation.

According to Young, center pivot users make three consistent mistakes: starting too late, untimely scheduling and overwatering. “The beauty of sensors is especially relevant to overwatering,” he says. “The sensors tell me when I’m good so I can hold back. The difference is real money.”

To learn about Tommy Young’s in-field research on irrigation scheduling techniques, visit

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