Researchers at the University of Colorado Boulder have developed a low-cost electronic sensor that can continuously monitor soil pH across a variety of soil types for months. This innovation, created by the Paul M. Rady Department of Mechanical Engineering, uses a pH-sensitive dye called alizarin, which changes color in response to pH levels. The sensor is designed on a circuit board, making it simpler to manufacture and connect with an affordable, portable readout system. This development could significantly improve soil monitoring in agricultural and environmental applications. The study, led by doctoral student Juan Cisneros Barba, was published in the journal Scientific Reports. The team tested the sensor in a range of soil types, including those with high organic matter, sandy or muddy compositions, and both compacted and loose soils. The results showed that the sensor provided consistent and accurate pH measurements over extended periods without requiring frequent recalibration. This reliability is a major improvement over existing sensors, which often need regular maintenance and recalibration. The new sensor’s design makes it more practical for outdoor use and distribution, especially in agricultural settings where monitoring soil conditions is essential for crop health and productivity. The technology relies on low-cost, battery-powered printed electronics, which are easier to produce and deploy in the field compared to traditional sensor systems. This advancement could lead to more widespread use of soil monitoring tools by farmers and environmental scientists. The research was led by Gregory Whiting, a professor and head of the Boulder Experimental Electronics and Manufacturing Laboratory (BEEM Lab). Whiting and his team are focused on developing practical, scalable electronic solutions for real-world applications. This latest work highlights their commitment to creating technologies that are not only innovative but also accessible and useful for agricultural and environmental monitoring.