Optical contact angle of air-dry soil samples

The optical contact angle of the samples was measured by attaching a one-grain layer of the air-dry soil sample to a piece op tape and release a drop of water onto it. The contact angle was determined from the image of the water drop on the soil (see supplementary pictures). The soil samples were taken from cover crop root channels and bulk soil six weeks after the cover crops had been terminated with a herbicide. Research domain: Soil Sciences Research question: How hydrophobic is the material in cover crop root channels.