Field Assessment of Soil Water Repellency Using Infrared Thermography
Abstract: This study aimed to evaluate the applicability of an infrared thermography technique relying on cooling the soil surface with cold water for assessing soil water repellency (SWR) severity under field conditions.
This study is a follow-up of earlier exploratory small-scale laboratory tests, where SWR spatial variability was mapped and repellent areas could be clearly detected on the thermal imaging due to their higher temperatures, thus distinguishing them from the remaining wettable areas.
Field tests were carried out, where both natural and artificial SWR were mapped through thermal imaging, using a portable infrared video camera. Cold water was used to create a temperature gradient on the soil surface in order to assess SWR.
Naturally repellent soils were found in a pine and eucalyptus forest and artificial SWR was induced with a waterproofing spray.
The molarity of an ethanol droplet (MED) test was used to measure both natural and artificial SWR severity.
The technique was, in overall terms, successful in mapping SWR spatial variability, distinguishing repellent from wettable areas as well as distinguishing different levels of SWR severity.
Only extensive testing can, ultimately, validate the technique and reveal its suitability in different field conditions (e.g., surface roughness, surface cover, spatial scale).