Mercury intrusion porosimetry of some New Zealand soils in relation to clay mineralogy and texture

Summary Pore size distributions in the 10/10 4 nm e.c.d. range in aggregates from three New Zealand soils with largely monomineralic clay fractions, were determined by mercury porosimetry after oven drying and also after critical point drying following methanol and then CO 2 exchange from a range of water contents. A soil containing halloysite showed considerable porosity in the fine pores (10–30 nm) regardless of the method of drying. A smectitic soil showed virtually no porosity in the 10 2 –10 4 nm range when oven dry. A soil containing allophane was dominated by large pores (> 10 3 nm). The change from a fine (clayey) to a coarser (clay loam) texture within the profile of one soil was reflected in an increase in large pores.