Drones help to redefine soil moisture monitoring

Radio waves could be used to measure soil moisture – helping farmers manage flood risk and make important decisions about irrigation.

A two-year project using drones carrying synthetic aperture radar equipment to make a high-resolution map of the earth’s surface is being undertaken by experts at Cranfield University.

Led by Dan Evans, the project is assessing the accuracy and potential applications of the technology to improve the accuracy of soil moisture monitoring by obtaining detailed measurements at a field scale level.

“By mounting synthetic aperture radar onto drones, we can conduct comprehensive radar surveys of fields, providing us with detailed measurements of soil moisture.”

The project seeks to improve flood and drought risk management, helping farmers make informed irrigation decisions and plan for extreme weather events. The technology could also find applications in testing the stability of railway embankments.

Flood and drought

The project also aims to identify the effectiveness of radar-based soil moisture measurements across different land use contexts, including grasslands, arable farmlands, and woodlands, says Dr Evans.

In addition to Cranfield University, the collaboration includes experts from the company Surveyar alongside other academic partners, with funding of £30,000 from the Douglas Bomford Trust.

Measuring soil moisture is often labour-intensive, time-consuming and costly. But the radar-equipped drones provide a way of continuously and cost-effectively measuring moisture up to 40cm below ground – a critical depth for plant growth and yield.

While preliminary findings suggest that UAV-based radar is effective at assessing soil moisture, the project will investigate the impact that above-ground vegetation has on the accuracy of these moisture data across different land use contexts.

With increasingly warm summers and the threat of extreme weather events, Dr Evans said monitoring soil moisture has become crucial for optimising irrigation practices and mitigating the impact of flooding.