Engineers at the University of Colorado Boulder have built a low-cost electronic sensor that monitors soil pH continuously and kept giving reliable readings for months when buried outdoors, a step towards farms that watch their own soil conditions around the clock. The study, led by doctoral student Juan Cisneros Barba in the Paul M. Rady Department of Mechanical Engineering, was published in Scientific Reports.

"In many cases, by the time farmers discover that something is wrong with their soil or plants, the window for effective treatment may have already passed," said Professor Gregory Whiting, who leads the Boulder Experimental Electronics and Manufacturing Laboratory. "Monitoring these factors continuously can help us better manage agricultural land and secure our food production."

Soil pH is often called agriculture's master variable because it governs nutrient availability and plant growth, but Whiting said conventional glass-bulb pH probes are fragile, drift over time and need frequent manual recalibration, which makes them poorly suited to soil. The team instead used an electrochemical sensor based on alizarin, a pH-sensitive dye, a technology it and others had shown works in simple settings and can be printed cheaply; the open question was whether it could monitor real soil for weeks or months.

To find out, the researchers buried sensors in soils that were organic-rich, sandy or muddy, and both compacted and loose, and moved to a printed-circuit-board design that is easier to manufacture, paired with an inexpensive field readout. Across the soil types the redesigned sensor delivered continuous pH measurements for months, and a multi-month outdoor test showed stable performance without constant recalibration.

"It's really just about usability," Whiting said. "These things cost close to nothing to make, function with minimal human effort and can be used in various soil types, allowing the technology to actually be useful in farms." The release is by Alexander Servantez of the University of Colorado Boulder, via EurekAlert.

Photo: CSIRO / Wikimedia Commons (CC BY 3.0)

Source: Morning Ag Clips