Soil crack volume estimates, which are important for hydrology models on
shrink-swell soils, are currently based on field measurements of vertical shrinkage and
an assumption of isotropic shrinkage; however, few studies have validated the resulting
crack volume estimates and studies have been limited to soils with very high shrink-swell
potentials. In addition, the spatial variability of soil cracking potential is not well
understood. First, I was able to improve in situ measurements of soil shrinkage by using
a single borehole for all vertical soil movement and water content measurements. Then
measurements of soil layer thickness and water content were made for seven soils with
varying COLE values, from 0.01 to 0.17 m m^(-1). Soil crack volume was estimated using
cement slurry and photographing excavated soil layers at the end of the study. Over
drying and wetting cycles, the relationship between soil layer thickness and water
content was linear. Modifying an existing crack volume equation with shrink-swell
potential and water content was a better fit to cement-estimated crack volume than the
unmodified estimates, improving the r^(2) from 0.06 to 0.84. The model over-predicted soil
crack volume by a factor of 10 and a minimum shrinkage volume was required to
generate visible soil crack volume. Finally, proximally-sensed bulk apparent electrical
conductivity was highly correlated to inorganic C, and the depth of maximum sensitivity
of the instrument was deeper than suggested by previous research in coarser textured
soils. Because inorganic C is related to shrink-swell potential, it may be possible to use
proximal sensors to map shrink-swell potential variability