Temporal variation in ped shape in an old pasture soil

Ped shape can influence soil physical properties by determining the morphology of interpedal pores. Monthly variation in soil ped shape was investigated in conjunction with soil physical properties for a pasture soil uncultivated for some years with the intension of identifying whether simple relationships existed between ped shape parameters and physical properties. A brief description of the ped shape quantification method used (Holden, 1993) and results obtained are presented, in conjunction with methods and data for hydraulic conductivity, soil water release, ped stability and microbial biomass determinations. Results indicate significant variation in ped surface roughness throughout one calendar year, but no significant changes in gross shape. Correlations between surface roughness and other soil properties are presented, the most important being the relationship identified between ped surface roughness and soil water characteristic data for a tension of 10 kPa. A significant correlation between ped shape and hydraulic conductivity could not be established. It is concluded that seasonally driven change in ped shape occurs, but that this is poorly related to bulk physical properties of the soil by simple relationships.