A reliable method for preserving soil structure in the field for subsequent morphological examinations

Examination of soil structure often requires that analysis takes place on samples that are representative of field conditions. A new method for the acquisition of undisturbed in situ soil samples for morphological analysis was developed. Small volumes (c. 100 cm3) were impregnated in the field by infiltrating a household varnish into the soil. Results indicated that the varnish readily penetrated to a depth of c.12 cm and hardened within seven days on a variety of soil textures. Following removal from the field, samples were re-impregnated using a standard polyester resin from which polished blocks and thin sections were produced in the conventional manner. No structural or optical artefacts associated with the varnish impregnation were observed. The technique is especially useful for studies where precise soil structural arrangement at the time of sampling is important, such as very friable soils or when examining of soil–root interactions.