SAIP2026

Assessing UAV Gamma-Ray Spectrometry for Soil Characterisation in Vineyards

8 Jul 2026, 11:00

20m

Lecture Hall GH2 (University of the Western Cape)

Oral Presentation Track B - Nuclear, Particle and Radiation Physics Nuclear, Particle and Radiation Physics -1

Speaker

Liam Delaney

Description

Soil texture is a fundamental parameter in agricultural systems, strongly influencing crop performance and informing soil management decisions. Accurate spatial mapping of soil texture, along with related physical and chemical properties such as bulk density, soil moisture, total organic carbon (TOC), and total nitrogen (TN), is therefore essential for effective and targeted cultivation practices. Traditionally, these properties are measured at discrete sampling points and subsequently extrapolated to larger areas. However, achieving reliable spatial representation requires extensive sampling, which is labour-intensive, time-consuming, and associated with high analytical costs.
Proximal sensing techniques offer a promising alternative for rapid and cost-effective soil characterisation at fine spatial resolutions. In particular, UAV-borne gamma-ray spectrometry (GRS) enables the acquisition of high-resolution radiometric data at low altitudes, which can be used to infer key soil properties through their relationship with naturally occurring radionuclides.
In this study, the potential of GRS for continuous soil property mapping was evaluated using a Medusa MS-350 portable gamma-ray spectrometer equipped with a custom-designed NaI(Tl) detector. The NaI(Tl) detector was mounted on the underside of a DJI Matrice 300 RTK UAV and flown at a fixed speed and altitude, while complementary ground-based measurements were acquired using a handheld Medusa system. This dual approach enabled both airborne and proximal data collection across the study area.
The investigation was conducted at Groote Post vineyard in Darling, approximately 80 km from Cape Town, South Africa. While previous studies have demonstrated the capability of proximal gamma-ray spectrometry to map soil texture at field scales, applications within vineyard environments remain limited. Vineyard soils are often highly heterogeneous at sub-plot scales, and structural features such as vine rows and canopy cover introduce additional complexities for radiometric measurements.
Following the radiometric survey, a total of 76 soil samples were collected and analysed in a laboratory for texture, bulk density, soil moisture, TOC, and TN. Previous studies (e.g., van der Veeke et al., 2021; Taylor et al., 2023) report contrasting findings regarding the predictive capability of GRS for soil properties. This study aims to address these discrepancies and provide a more definitive assessment of the potential of UAV-based and proximal gamma-ray spectrometry for predicting soil physical and chemical properties in heterogeneous vineyard systems.