This paper proposes and implements an energy-efficient battery-powered IoT system to monitor soil for macronutrients. Each measurement node is comprised of a development board, a sensor to measure the N, P and K concentrations in soil, a GPS module to acquire the geolocation and a power relay to cut power in order to conserve battery. The acquired data is displayed on a Node-RED dashboard with geographic and concentration data tracking capabilities for each node, with the possibility to consult historic data. The system was validated locally by monitoring soil conditions for plants.

--