University of Wisconsin–Madison engineers have created affordable sensors that can continuously monitor nitrate levels in Wisconsin’s common soil types. These innovative printed sensors could help farmers make better decisions about managing nutrients, leading to increased crop yields and cost savings.
“Our sensors offer farmers valuable insights into their soil’s nutrient levels and nitrate availability for plants, empowering them to optimize fertilizer use,” explains Joseph Andrews, an assistant professor of mechanical engineering at UW-Madison. “Reducing fertilizer usage can result in significant savings for large-scale farms.”
While nitrate is crucial for crop growth, excessive levels can pollute groundwater, posing risks to human health and the environment. The new sensors developed by the researchers could also serve as a tool for studying nitrate leaching and promoting practices to minimize its negative impacts.
Current methods for monitoring nitrate levels in soil are costly, labor-intensive, and lack real-time data. This inspired Andrews and his team to create a more efficient and cost-effective solution.
Using an inkjet printing process, the researchers manufactured potentiometric sensors, a type of thin-film electrochemical sensor commonly used to measure nitrate in liquid solutions. However, these sensors were not originally designed for use in soil environments due to potential interference from soil particles.
To address this challenge, the team introduced a layer made of polyvinylidene fluoride over the sensors. This material features tiny pores that allow nitrate ions to enter while blocking soil particles. Additionally, it is hydrophilic, which helps absorb water, creating an environment conducive to accurate nitrate sensing.
The researchers published their findings in March 2024 in the journal Advanced Material Technologies.
The sensors were successfully tested in two different soil types found in Wisconsin – sandy soil and silt loam soil – demonstrating accurate results. The team is now integrating these nitrate sensors into a “sensing sticker” system that includes moisture and temperature sensors.
By using sensing stickers attached to a rod buried at various depths in the soil, the researchers can track nitrate, moisture, and temperature levels. This approach allows for a comprehensive understanding of nitrate leaching processes and movement within the soil.
In the summer of 2024, the researchers plan to deploy 30 sensing rods at UW-Madison’s Hancock Agricultural Research Station and Arlington Agricultural Research Station for further testing. The team is also seeking to patent their technology through the Wisconsin Alumni Research Foundation.
Co-authors from UW-Madison include Kuan-Yu Chen, Aatresha Biswas, Shuohao Cai, and Jingyi Huang, a professor of soil science.
This research received support from the USDA Agriculture and Food Research Initiative Foundational Program (project no. WIS04075), the National Science Foundation Signals in the Soil grant 2226568, and the University of Wisconsin-Madison Dairy Innovation Hub.
