Printed sensors in soil could help farmers improve crop yields and save money

College of Wisconsin–Madison engineers have developed low-cost sensors that permit for real-time, steady monitoring of nitrate in soil sorts which are frequent in Wisconsin. These printed electrochemical sensors might allow farmers to make higher knowledgeable nutrient administration choices and reap financial advantages.

“Our sensors might give farmers a higher understanding of the nutrient profile of their soil and the way a lot nitrate is accessible for the vegetation, serving to them to make extra exact choices on how a lot fertilizer they actually need,” says Joseph Andrews, an assistant professor of mechanical engineering at UW–Madison who led the analysis. “If they’ll purchase much less fertilizer, the fee financial savings may very well be fairly vital at large-acreage farms.”

Whereas nitrate is an important nutrient for rising crops, extra nitrate can leach out of soil and into groundwater. This sort of air pollution is harmful for individuals who drink contaminated effectively water and is dangerous for the atmosphere. The researchers’ new sensors may be used as an agricultural analysis software to observe nitrate leaching and assist information greatest practices for mitigating its dangerous results.

Present strategies for monitoring nitrate within the soil are laborious, costly and don’t present real-time information. That’s why Andrews, an professional in printed electronics, and his staff got down to create a greater and less expensive answer.

One of many researchers’ multifunctional sensing stickers, which incorporates sensors for measuring nitrate, moisture and temperature. Photograph by Joel Hallberg

From left: ECE graduate college students Kuan-Yu Chen, Sharar Muhtasim, Jeneel Kachhadiya, and Assistant Professor Joseph Andrews holding a rod with three multifunctional sensing stickers connected. Photograph by Andrew Hallberg

The researchers’ sensing rods with multifunctional sensing stickers positioned to allow multi-depth measurements when they’re positioned within the soil. Photograph by Joel Hallberg

A sensing rod put in in soil at UW–Madison’s Hancock Agricultural Analysis Station. Photograph by Kuan-Yu Chen

For this challenge, the researchers used an inkjet printing course of to manufacture potentiometric sensors, a sort of thin-film electrochemical sensor. Potentiometric sensors are generally used to precisely measure nitrate in liquid options. Nevertheless, these sensors aren’t sometimes appropriate to be used in soil environments, the place coarse soil particles will scratch them and intrude with acquiring correct measurements.

“The primary problem we had been making an attempt to resolve is determining a technique to allow these electrochemical sensors to work effectively within the harsh atmosphere of soil and precisely sense nitrate ions,” Andrews says.

The staff’s answer was to position a layer over the sensor constituted of polyvinylidene fluoride. Andrews says this materials has two key options. First, it has very tiny pores, about 400 nanometers in measurement, that permit nitrate ions to move via whereas blocking soil particles. Second, it’s hydrophilic, that means it attracts water and acts like a sponge to soak up it.

“So, any nitrate-laden water will get preferentially soaked into our sensor, and that is actually essential as a result of soil additionally acts like a sponge, and also you’re going to have a dropping battle for getting moisture to return to your sensor except you’ll be able to match the water absorption potential of soil,” Andrews says. “These options of the polyvinylidene fluoride layer allow us to extract the nitrate-laden water, get it to the floor of our sensor and precisely sense nitrate.”

The researchers detailed their advance in a paper revealed in March 2024 within the journal Superior Materials Applied sciences.

The staff has examined its sensors in two totally different soil sorts which are related for Wisconsin — sandy soil, which is frequent within the north-central a part of the state, and silt loam soil, which is frequent in southwestern Wisconsin — and located that the sensors produced correct outcomes.

The researchers are actually incorporating their nitrate sensors right into a multifunctional sensing system they name a “sensing sticker,” by which three totally different sorts of sensors are mounted on a versatile plastic floor with an adhesive on the again. These stickers additionally comprise moisture and temperature sensors.

The researchers will connect a number of sensing stickers to a rod, positioning them at totally different heights, after which bury the rod within the soil. This setup permits them to take measurements at a number of depths within the soil.

“By measuring the nitrate, moisture and temperature at totally different depths, we are able to now quantify the method of nitrate leaching and seize how nitrate is shifting via the soil, which hasn’t been potential earlier than,” Andrews says.

In summer time 2024, the researchers plan to conduct additional testing with their sensors by deploying 30 sensing rods within the soil at UW–Madison’s Hancock Agricultural Analysis Station and Arlington Agricultural Analysis Station.

The researchers are patenting their expertise via the Wisconsin Alumni Analysis Basis.

UW–Madison co-authors on the paper embody Kuan-Yu Chen, Aatresha Biswas, Shuohao Cai, and Jingyi Huang, a professor of soil science.

This analysis was supported by the USDA Agriculture and Meals Analysis Initiative Foundational Program (challenge no. WIS04075), the Nationwide Science Basis Alerts within the Soil grant 2226568, and the College of Wisconsin–Madison Dairy Innovation Hub.