Plant Spike: A Low-Cost, Low-Power Beacon for Smart City Soil Health Monitoring

Plant Spike is an in situ low-cost sensor system that is wireless, miniature, and low powered. It can be seamlessly implanted in subsurface locations across major cities to measure urban soil health. Plant Spike incorporates noncontact soil moisture monitoring, temperature monitoring, light intensity monitoring, advanced power management, and Bluetooth low energy transmit-only communication for transmitting information to a client device. With a novel combination of aggressive power reduction techniques, the system's lifetime is over two years with a 500-mAh battery. By connecting on-board sensors to a single-chip microcontroller, the total component and assembly cost of each module is less than $10. The sensor system has been tested within an urban soil testbed located on Columbia University's Morningside Campus in New York City as well as street tree pits located in Morningside Heights, proving the functionality and robustness of the system. Plant Spike is able to measure temperature and light ranges that are comparable to the fluctuations experienced by soils located within the climate zone of New York City.