ABSTRACT
Porosity, pore shape and pore size distribution were measured on thin sections prepared from undisturbed soil samples by means of electro-optical image-analysis. Soil samples were taken from the topsoil compacted by the tractor wheels and in uncompacted topsoil, and just below the tilled layer where the ploughpan or ploughsole was developed.
In the compacted topsoil the porosity strongly decreased, particularly the irregular pores while the elongated ones strongly reduced their size and modified their orientation pattern. The microscopic observation revealed that these elongated pores were thin fissures parallel to the soil surface, thus giving rise to a platy structure, and very often they lòst their continuity in a vertical sense. After one year there were no visible differences between the compacted and uncompacted topsoils. The ploughpans were very thick (in many cases more than 10 cm) but it was the first cm that was more strongly compacted and contained few, if any, pores.
