These Wirelessly-Powered Soil Moisture Sensors Feed the Earth When Growing Season's Done
Made with fertilizer in the substrate, these sensors transmit soil moisture data as heat and feed the crops when they're done.
A research team from Osaka University is looking to make agriculture more sustainable with a network of wirelessly-powered smart soil sensors which can degrade into fertilizer to enrich the soil when they're no longer required.
"Our system comprises several sensors, a wireless power supply, and a thermal camera for acquiring and transmitting sensing and location data," says Takaaki Kasuga, lead author of the work detailing the environmentally friendly approach to data-driven agriculture. "The in-soil components are largely eco-friendly, composed of a nanopaper substrate, a natural wax protective coating, a carbon heater, and tin conductive lines."
The idea of monitoring the soil with electronic moisture sensors isn't new, but poses a problem: you have to retrieve the sensors when they reach end-of-life, so that the materials from which they're made — and in particular the batteries driving them — don't pollute the very soil they were supposed to monitor.
Kasuga's team approached the problem differently. The monitoring system still involves a number of moisture sensors inserted directly into the soil, but they lack batteries. Instead, they're powered wirelessly — and the efficiency of that power transmission is affected by the moisture content of the soil. The sensors which receive less power heat up less, a change which is monitored by a thermal camera and from which the moisture content of the soil in which each sensor is inserted can be measured.
"We have successfully visualized areas of soil moisture deficit by using 12 sensors in a 0.4-meter by 0.6-meter [around 1.3 feet by two feet] demonstration field," Kasuga says of his team's work on the project. "Thus, our system works at the high sensor densities needed for precision agriculture."
To further improve the green credentials of the system, the sensors themselves are biodegradable — and are designed to be tilled into the soil at the end of the growing season. As they degrade, they release fertilizer from their substrate material, enriching the soil they once monitored and readying it for the next growing season.
The team's work has been published under open-access terms in the journal Advanced Sustainable Systems.