Design and evaluation of an aerial vehicle payload for automated near-surface soil moisture measurements

Measuring near-surface soil moisture across large agriculture fields presents challenges when repeated data are required. Remote sensing approaches can model estimates of soil moisture across large areas; however, calibration and validation data are often needed. An automated near-surface soil moisture measurement payload was developed for deployment on aerial vehicles to address the challenges of measuring near-surface soil moisture across large agriculture fields. This system, integrating a capacitance-based soil moisture probe (Version 1) and a control/data acquisition system, underwent field testing and was later enhanced with a time-domain reflectometry (TDR) sensor with a 5 cm probe (Version 2) for improved performance. Version 2 achieved full system autonomy, enabling multiple soil moisture measurements upon landing, focusing on near-surface soil moisture data (0–5 cm). Soil moisture measurements are stored in internal memory on the payload, and a post-processing workflow was developed to obtain geotagged measurements. Results from testing Version 2 in Utah demonstrated the platform’s capability to reliably obtain near-surface soil moisture measurements with success rates exceeding 85% when there was sensor insertion greater than 4.5 cm. The depth of sensor insertion was influenced by soil moisture, texture, and compactness, with challenges observed in hard dry surfaces. Despite these challenges, this innovative system offers a solution for automated in situ, near-surface soil moisture measurements across different fields, providing ease of deployment, automation, and repeatability. •First-of-its-kind UAV payload measures soil moisture at >85% accuracy when inserted >4.5 cm.•Integrated embedded device and microcontroller with flight controller for full autonomy.•Proposed system can be deployed to collect ground truth data for remote sensing models.