Wireless sensors manage water use with text messages

Researchers from the University of California, Davis, have developed a wireless monitoring system for flood-irrigated crops that sends a cellular text message when it is time to turn off the water to minimize drainage. The system uses wireless sensors that are placed above ground in the irrigated field.

Shrini Upadhyaya, professor of biological and agricultural engineering at UC Davis, is one of the researchers. He said the nuts and bolts of the system consist of a central unit and wireless sensors. The central unit is placed near the field being irrigated and monitors the sensor in the field.

When irrigation water arrives at the sensor, it will generate a signal that is sent to the central unit through wireless communication. That, in turn, will generate a cellular text message to the irrigator to turn off the water, Upadhyaya said.

Instead of the irrigator making multiple trips to the field to check water, he only has to go once, Upadhyaya said.

The system is portable so it can be moved from field to field.

"If they're irrigating four checks today, they put sensors in those four checks. If they're going to irrigate somewhere else the next day, they just move them to those checks," Upadhyaya said.

There has been a lot of interest in this technology, but currently there are only four units, he said: one in McArthur, one in Winters, one in the San Joaquin Valley and one at Davis.

"Three of the units are with the farmers that helped us put it together, and we get feedback from them," Upadhyaya said.

George McArthur, a partner of McArthur Livestock in McArthur, uses the system on flood-irrigated timothy, pasture and mint.

"We've been using them, and we love them," McArthur said, adding the major benefit is the time savings, which equates to labor savings.

"Where it really works good for our irrigators is as we do our crop rotation," he said, saying his irrigators don't know how long it will take the water to make those runs because of the variability in them.

"It saves those guys a tremendous amount of time in having to come back, and back, and back, and check," McArthur said. "Now, they can go home at night and sleep until they receive the text."

He said the system paid for itself in the first year.

Originally, the sensors were buried because of grower preference, but two things happened to change that, Upadhyaya said. First, the price of copper wire skyrocketed. Second, concerns arose about rodents potentially getting into the system.

"When we first started it, wireless technology had lots of limitation," Upadhyaya said, but by the time the system was finished, advances in technology made it easier to go wireless.

There are actually two systems. The simple system growers are currently using allows them to place the sensor where they want it, and it generates a text message when the water arrives at that point. The advanced system tells the irrigator exactly when to turn the water off.

"That means the water arrives at the sensor, it makes some computations, and then tells you in how many minutes from now—say, 45 minutes—you should go and turn the water off," Upadhyaya said.

Future research may include telling irrigators when the field is dry, he said.

"I think we could certainly do that with our system. We could not only tell when to stop irrigating, we could also tell when to start irrigating, all through the text messaging system," Upadhyaya said.

The system has a couple of issues that are being addressed, he said, including a radio transmitter that only has about a half-mile range.

Michael Turkovich of Button and Turkovich Farms in Winters said he used the system this year in alfalfa and for the most part he likes it.

"We're still working out some issues," Turkovich said, adding his main issue has been with the signal range.

Ideally, Turkovich said he wants the system to have a wider range so it could be left at the shop, where it could cover all of his fields.

"Right now we have to move it because not all our fields are within a mile of each other," he said.

The other issue is that the battery on the central unit has to be recharged every couple of days, Turkovich said.

"We're thinking about getting a solar panel to put on that central unit to maybe help with that issue," he said.

Turkovich said he's hopeful that down the road there will be a labor savings and that he will have more efficient water use.

Upadhyaya said researchers are working to build repeaters to extend the range of the signal, which will cost about $300 each.

To build the current system, it costs Upadhyaya about $1,200 for the central unit and about $300 for each sensor, with typically four sensor units per system, for a total cost of around $2,500.

"There's quite a bit of interest in it, but we don't have the ability to manufacture it right now and supply it to the farmer. We haven't established a mechanism for that yet," he said.

(Kathy Coatney is a reporter in Corning. She may be contacted at kacoatney@gmail.com.)