University of Nebraska–Lincoln Extension educator Gary Zoubek shows how a typical water sensor setup might look in the field.  

Remote water sensor technology saves water and money

Farmers understand how precious water is as a resource, but that point was driven home even further during the historical drought of 2012. Farmers such as Ryan Weeks and Leon Knirk have embraced a simple, yet effective, technology to help optimize their irrigation strategy—water sensors. Using these sensors creates an opportunity to change irrigation from a guessing game to a numbers game.

"You just use a soil probe to make a hole, and then stick the sensors in at 1', 2' and 3'," says Weeks, who farms corn and soybeans in Nebraska. "Then you use a monitor to measure the moisture of your soils at 1', 2' and 3'. The University of Nebraska has done a lot of research to determine when you need to start watering based on the sum of those three numbers."

Knirk, who farms in south-central Michigan, says he’s used his sensors for two years and is still fine-tuning his processes, but says that just gaining a baseline amount to work from has been valuable.

"I had something to look at," he says. "I had a number. I wasn’t just taking a shovel out and trying to turn over some soil and make a guess at it. I had some kind of tool that wasn’t just an estimation."

Soil moisture measurement is important in any year, but it’s especially critical in light of this summer’s drought-choked conditions.

What’s more, soil moisture is never steady. It is based on a number of obvious elements such as rainfall and temperature. Soil moisture is also influenced by less obvious factors, such as no-till practices, which help with water retention, and the planting of newer hybrids that are more efficient users of water.

To that end, Knirk says, it can matter greatly where the water sensors are placed in each field. Zone-mapping his fields helped him choose smart locations for his water sensors, he says.

"We tried to get them on zones that were relatively large in our field. I didn’t go to the absolute driest zone in the field, but I went into one of my drier zones that was a relatively large portion of the field. We used that for a measuring tool because I knew if my moisture levels had fallen there, I had a buffer for the rest of the field that had better water-holding capacity," Knirk says.

Weeks adds that his monitors have allowed him to map out a smarter irrigation schedule. Oftentimes, better monitoring means fewer pivot trips, he says.

"Most years, I think this has saved me at least two applications," he says. "We’re talking $750 to $1,000 per pivot, per circle. We have estimated that [has saved us a total of] 500 gal. of diesel, 145 hours of operation on the motor and 22.68 million gallons of water."

How it works. Using the water sensors and monitors is not a difficult process. Every time farmers take a reading from the water sensors, they get a readout from 1 to 200, says Tom Penning, president of Irrometer Company, Inc., which manufactures Watermark sensors and handheld meters. Other companies, such as Memsic and ETgage, offer similar products.

To imagine how soil water tension works, think about a sponge, Penning says. If you have a sponge that is completely saturated, it takes almost no effort to begin extracting water. But as water continues to leave the sponge, it becomes more and more difficult to squeeze out the remaining moisture.

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