Pore-size distributions of some New Zealand soil groups

Abstract

Abstract The volumes of soil pores in five size classes have been determined for 88 profiles of New Zealand soils by draining core samples under tensions up to 1000 cm of water. In most samples pores with diameters greater than 60 μm occupied more volume than pores between 60 and 3 μm in diameter. Most soil groups had similar distributions of pore sizes in the range from 60 to 3 μm, but a few groups had exceptionally large volumes of pores close to 60 μm in diameter. The percent volumes of pores in the various size classes generally decreased with increasing depth in the soil. Yellow-brown loams, formed on recent andesitic ash, were generally more porous than the other soil groups studied. Other significant differences among soil groups were found mainly for particular pore sizes and depths in the profile. The brown granular clays of North Auckland, derived from the oldest andesitic materials in New Zealand, were no more porous than many soils from loess or sedimentary rocks.