Is High-Tech Subsurface Moisture Monitoring on the Way?

Purdue University has developed technology that researchers say could be used by farmers in the future to more accurately sense subsurface moisture by measuring the reflections from communication satellite signals.

“The reflectivity of the surface is a function of the soil moisture, and that allows us to quantify the amount of moisture in the soil, so if necessary, growers can take corrective actions to protect their crops,” according to Purdue professor of aeronautics James Garrison. “Managing the water that is available is becoming increasingly important. To manage it, you need to be able to accurately determine the amount being used.”

Researchers used a specialized receiver that captures reflections of communication satellite signals with 1-meter wavelengths. Scientists call this the “P Band,” which can measure soil moisture 6” to 8” below the surface of the soil. That’s a marked improvement from current satellite observations of soil moisture, which can only penetrate about 2”. Researchers dubbed the technique SoOp, short for “signals of opportunity.”

Garrison says the technology is relatively cost-effective and portable.

“By using these existing satellite signals, we bypass the requirements for licensing a P Band transmitter, which is extremely difficult,” he says. “It also reduces the size of the antenna required.”

The signals are currently collected by flying the prototype instrument on a small plane. Next, researchers plan to collect data from a fixed tower location so they can monitor crop changes over at least one growing season. Theoretically, a commercial product could be mounted on drones so it could collect the necessary data.

Purdue’s Office of Technology Commercialization patented the technology, and is currently offering it for licensing.