A two-dimensional quantification of soil ped shape

SUMMARY Quantification of soil ped shape is discussed from three viewpoints: 1 The theoretical reasons why quantification of ped shape should be useful (objective classification of shape, improved understanding of ped/pore relationships, soil genesis and ped development and as a measure of soil heterogeneity); 2 The theoretical division of irregular shape into three components (circularity, angularity and surface roughness) and how circularity and surface roughness can be quantified using Cox's R-statistic and the Fractal dimension (D). Angularity remains unquantified; 3 The testing of a computer program written to quantify ped shape against six criteria that were presented (Clark, 1981) to allow an assessment of shape quantification methods and the calibration of the program using Pettijohn's (1 957) standard shape chart. It is concluded that R and D are able quantifiers of irregular particle shape.