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Engineers, plant scientists decode electrochemical soil signals

By Seth Truscott, College of Agricultural, Human, and Natural Resource Sciences

Seeking new tools to improve soil health, scientists at Washington State University are studying electric signals that bounce between plants and the underworld community of microbes that sustain them.

As part of the $1.2 million National Science Foundation-funded research project, a cross-disciplinary team of WSU engineers and crop scientists will sink electrodes into Washington wheat fields and soil-filled containers in the lab this spring. Their discoveries could help farmers and scientists measure and support beneficial exchanges in the soil.

“Microorganisms are essential for plants,” said co-lead scientist Haluk Beyenal, professor in the Gene and Linda Voiland School of Chemical Engineering and Bioengineering. “Crops need them to stay healthy.”

Plants have a symbiotic relationship with soil bacteria. Microbes help exchange nutrients and stimulate plant growth, and their presence is key to soil fertility.

“Our research uses electrochemically active microbes as proxies for soil health,” Beyenal said. “Electrochemical signals can tell us what plants and microbes need.”

In the soil, bacteria make electrochemical exchanges with plant roots, grabbing free electrons for use in their metabolism. This exchange can be detected electrochemically: the team’s carbon-fiber electrodes act as an electron-producing source, with bacteria attaching themselves to the probes as a gooey biofilm.

“A lot of biology happens beneath the surface,” said co-primary investigator Maren Friesen, a WSU plant pathologist who is working to identify beneficial bacteria at work.

Friesen’s team are sampling and sequencing these communities, while engineers study the resulting signal data. Together, the group of faculty and student scientists aim to piece together how signals relate to soil health and plant productivity.

“We’re trying to extract the rules of soil electrochemistry: how microbes interact with the soil and the plant and what signals are being exchanged,” said co-lead investigator Anantharaman Kalyanaraman, professor and Boeing Chair of Computer Science in the School of Electrical Engineering and Computer Science.

Along with a software model that can interpret signals and predict microbe activity and plant function, researchers aim to develop sensors or other technologies that could help farmers and scientists monitor the soil microbiome.

“If we can measure what’s happening in soil, we could shift microbial communities,” Beyenal said. Such control could, for instance, help growers precisely apply nitrogen fertilizer, minimizing farmer expense and environmental impact.

Relying on the work of several doctoral and undergraduate students, the project is an opportunity to exchange ideas and cross-train.

“The future of science and our workforce depends on cross-disciplinary collaborations,” Beyenal said. “We’re more than the sum of our parts, and none of us could do this alone.”

The four-year project launched in winter 2023 and continues through 2026. Envisioning new discoveries spinning off from the project, the team’s long-term goal is better communication on soil health.

“Soil is the skin of the earth,” Friesen said. “It produces food, fiber, and fuel, filters water, and helps break down pollutants. It does so much for us that it’s important to learn more about how we can keep it healthy.”

“What would we have without soil?” Beyenal asked. “Everything we grow depends on it.”