Fertilizers containing nitrogen are used to increase food production, but their emissions can pollute the environment. To maximize resource use, increase agricultural yields and reduce environmental risks, continuous and real-time monitoring of soil properties, such as soil temperature and fertilizer emissions, is essential. A multi-parameter sensor is needed for smart or precision farming to monitor NOX gas emissions and soil temperature for the best fertilization.

James L. Henderson, Jr. Memorial Associate Professor of Engineering Science and Mechanics at Penn State Huanyu “Larry” Cheng led the development of a multi-parameter sensor that successfully separates temperature and nitrogen signals to enable accurate measurement of each.

Cheng said, “For efficient fertilization there is a need for continuous and real-time monitoring of soil conditions, in particular nitrogen use and soil temperature. This is essential for evaluating crop health, reducing environmental pollution and promoting sustainable and precision farming.”

The aim of the research is to use the right amount for the best crop yield. The production of the crop can be lower than when more nitrogen is used. When fertilizer is applied in excess, it is wasted, plants can burn, and toxic nitrogen fumes are released into the environment. Farmers can achieve the ideal fertilizer levels for plant growth with the help of accurate detection of nitrogen levels.

Co-author Li Yang, a professor at the School of Artificial Intelligence at China’s Hebei University of Technology, said: “Plant growth is also influenced by temperature, which influences the physical, chemical and microbiological processes in the soil. Continuous monitoring enables farmers to develop strategies and interventions when temperatures are too high or too low for their crops.”

According to Cheng, sensing mechanisms that can obtain nitrogen gas and temperature measurements independently are rarely reported. Both gases and temperature can cause variations in the sensor’s resistance measurement, making it difficult to tell them apart.

Cheng’s team created a powerful sensor that can detect nitrogen loss independent of soil temperature. The sensor is made of vanadium oxide-doped, laser-induced graphene foam, and doping metal complexes in graphene have been found to improve gas adsorption and detection sensitivity.

Because a soft membrane protects the sensor and prevents the ingress of nitrogen gas, the sensor only responds to temperature changes. The sensor can also be used without encapsulation and at a higher temperature.

This allows accurate measurement of the nitrogen gas by excluding the effects of relative humidity and soil temperature. With the included and non-encapsulated sensors, temperature and nitrogen gas can be completely disconnected without interference.

The researcher said decoupling temperature changes and nitrogen gas emissions could be used to create and deploy multimodal devices with decoupled sensing mechanisms for all-weather precision farming.

Cheng said, “The ability to simultaneously detect ultra-low nitrogen oxide concentrations and small temperature changes paves the way for the development of future multimodal electronic devices with decoupled sensing mechanisms for precision agriculture, health monitoring and other applications.”

Cheng’s research was funded by the National Institutes of Health, the National Science Foundation, Penn State and China’s National Natural Science Foundation.

Magazine reference:

  1. Li Yang. Chuizhou Meng, et al. Vanadium oxide-doped laser-induced graphene multi-parameter sensor to decouple soil nitrogen loss and temperature. Material ahead. DOI: 10.1002/adma.202210322