ABSTRACT
Air permeability and diffusion of Krypton-85 gas were measured in soil cores of differing bulk densities and degrees of saturation. Relative diffusivities reveal directly the conditions under which soil aeration becomes inadequate for arable crops. The spatial variability of air or water permeability may be estimated from air or water-filled porosities by using the relationship between air permeabilities and air-filled porosities. Relative diffusivity and air permeability may be used separately to calculate empirical continuity indices. Combination of the two measurements with air-filled porosities allows estimation of the radius, the variation of radius and the tortuosity of the continuous paths of soil pores. Measurements of samples taken at intervals after compaction show recovery from compaction which is not necessarily indicated by measurements of soil porosity or bulk density.
