Image analysis and fractal geometry to characterize soil desiccation cracks

The rapid transport of water and solute through desiccation soil cracks can lead to crop water and nutrient stress as well as ground and surface water contamination. The objectives of this research were to determine (1) soil surface crack area, (2) fractal dimension of crack edges (D1), and (3) mass fractal dimension (D2) and lacunarity of soil surface cracks. Photographs were used to record in situ soil cracking in a Mexico silt loam (fine, smectitic, mesic Vertic Epiaqualf) at two locations for three sampling dates. Photographs of the cracks were digitized and an algorithm was developed to determine crack area, and the fractal dimension and lacunarity of the digitized images. Location 1 produced 7% crack area, a mass fractal dimension (D2) of 1.44, and a crack edge fractal dimension (D1) of 1.08. Location 2 produced 25% crack area, a mass fractal dimension (D2) of 1.64, and a crack edge fractal dimension of 1.08 (D1). Lacunarity curves as a function of box size for crack boundary fractal dimension were more variable at location 2. Soil profile moisture content and texture analysis indicated the presence of an argillic horizon at the 20-cm depth at Location 1 while at Location 2 the argillic horizon was exposed to the soil surface. Photographic image analysis techniques and fractal analysis appear to distinguish differences in crack area and patterns which may be useful in characterizing soil cracking.