Colleen Josephson, an assistant professor of electrical and computer engineering at University of California, Santa Cruz, has built a prototype of a passive radio-frequency tag that could be buried underground and reflect radio waves from a reader aboveground, either held by a person, carried by a drone or mounted to a vehicle. The sensor would tell growers how much moisture is in the soil based on the time it takes for those radio waves to make the trip.
Josephson’s goal is to boost the use of remote sensing in irrigation decisions.
“The broad motivation is to improve irrigation precision,” Josephson said. “Decades of studies show that when you use sensor-informed irrigation, you save water and maintain high yields.”
However, current sensor networks are expensive, requiring solar panels, wiring and internet connections that can run thousands of dollars for each probe site.
The catch is the reader would have to pass within proximity of the tag. She estimates her team can get it to work within 10 meters aboveground and as low as 1 meter deep in the ground.
Josephson and her team have built a successful prototype of the tag, a box currently about the size of a shoebox containing the radio frequency tag powered by a couple of AA batteries, and an aboveground reader.
Funded by a grant from the Foundation for Food and Agriculture Research, she plans to replicate the experiment with a smaller prototype and make dozens of them, enough for field trials on commercially managed farms. The trials will be in leafy greens and berries, because those are the main crops in the Salinas Valley near Santa Cruz, she said.
One aim is to determine how well the signal will travel through leafy canopies. So far, at the station, they have buried tags adjacent to drip lines down to 2.5 feet and are getting accurate soil readings.
Northwest irrigation experts lauded the idea — precision irrigation is indeed expensive — but had many questions.
Chet Dufault, a grower who uses automated irrigation tools, likes the concept but balked at the labor needed to bring the sensor into proximity of the tag.
“If you’re having to send someone or yourself … you can stick a soil probe in 10 seconds just as easy,” he said.
Troy Peters, biological systems engineering professor at Washington State University, questioned how soil type, density, texture and bumpiness affect readings and whether each location would need to be individually calibrated.
Hundreds of sensors, installed and maintained by company technicians, communicate by radio with a single receiver powered by a solar panel up to 1,500 feet away, which then transfers data to the cloud. Battery life is not a problem, because those technicians visit each sensor at least once a year.
Josephson’s prototypes hearken back 30 years, said Ben Smith, technical irrigation specialist for Semios. He remembers buried with exposed wires that a worker would physically plug into a handheld data logger.
Today’s sensors can break down data on water, nutrition, climate, pests, and more. For example, the company’s soil detectors take measurements every 10 minutes, allowing analysts to spot trends.
Post time: May-06-2024