Soil moisture sensing with mmWave radar

Soil moisture is a significant factor that influences plant productivity and natural resource management. Accurate commercial soil moisture sensors often require manual data collection and cost thousands of dollars, which makes data collection inefficient and only accessible to high-budget smart farms. To achieve cost-effective and high-efficient soil moisture sensing, we propose a millimeterwave (mmWave) radar-based method, which can obtain the soil moisture from the propagation time and Angle of Arrival (AoA) of the reflected signals received at multiple antennas. Our method only requires a single Commercial-Off-The-Shelf (COTS) mmWave radar to automatically estimate the soil moisture level. Our experiment in outdoor environments shows that the proposed system produces a mean absolute error of 2.2% volumetric water content (VWC), demonstrating the feasibility of the low-cost non-contact soil moisture sensing for smart farming.