Soil Moisture Sensors An Open Secret Of Profitability

Chris Henry, center, prepares ground while Tommy Young, left, and Greg Simpson wait to place and connect moisture sensors. ( Chris Bennett )

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

In an age of anemic crop prices, profitability demands precise water management. Cutbacks to fertilizer, seed rates or chemicals are a big ask for many growers, but water is prime for a crop per drop approach. With a relatively tiny investment in irrigation technology, immediate savings are on tap.

pvcChris Henry, associate professor and water management engineer at the University of Arkansas (UA) Rice Research and Extension Center (RREC) 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? That answer is hard to quantify, but try to find someone that has had a planter population monitor and traded it off for one without. The exact same principle applies to soil moisture sensors.”

Despite the concrete dollar returns of precision irrigation management, many growers still rely on the vagaries of foot scrapes or shovel-and-eyeball methods. For growers interested in irrigation automation and a reduction in uncertainty, Henry recommends starting simple: “Begin with inexpensive Watermark sensors and get comfortable. There’s a wide range of sensors to buy, but just start with something that makes sure you’re using the right amount of water and meeting crop demand.”

“There’s so much irrigation help out there. Go talk to county agents or contact the NRCS. Start with moisture sensors. Take one field and try it out to discover how things work,” Henry advises.

tyFour 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 (Soil Sensor Calculator) designed by Henry, the sensor data is entered and converted to how much water is available according to soil type. Once calculated, irrigations predictions are simplified. “For example it (the app) reports that you have 1” of plant available water, so at a quarter-inch per day of crop water demand, we need to be finished irrigating the field in four days. It’s that simple. With a little bit of PVC, guys in the shop can make sensors in the winter instead of sitting on a bucket. This is old technology, but very cost-effective,” Henry says.

When a pivot makes a 40-hour turn and drinks 4 gallons of diesel per hour ($2.50 per gallon), the cost for a single revolution is a painful $400. Henry is adamant: Soil moisture sensors can save growers several turns on a single pivot or several sets in furrow irrigation. “Moisture sensors tell you exactly how much water is in the profile. In the right circumstances, moisture sensors can save a turn in a single week. Beyond diesel savings, remember that equipment, labor, time, and pickup trips are all affected,” 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 (IWMP) in the fall and they’ll pay 50%-80% of all costs.”

See also, Crop Per Drop Contest: May The Best Farmer Win

Greg Simpson, irrigation program associate with the UA Division of Agriculture, echoes Henry regarding the advantages of sensor-driven irrigation: “I guarantee you will sleep better at night using soil moisture sensor information to make an irrigation call, rather than relying on experience or guesswork. You get more efficient the second you start using sensors because of time, labor and money.”

sensorsProducer Tommy Young (Young’s Irrigation & Equipment) runs 21 pivots separated by 27 miles of drive time in Jackson County, Ark. Spurred by Henry, Young began widespread implementation of soil moisture sensors in 2016. The results, according to Young, have transformed his operation.

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

Henry points toward the logical fallacy of tracking the precise expense and application of fertilizer, seed or chemicals, yet allowing water to remain behind a perpetual question mark. “Some growers say, ‘I already know how to irrigate.’ Why not spend just $150 on soil moisture sensors and make sure you’re getting enough water out on time?”

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