ARS | Publication request: Challenges and limitations in studying the shrink-swell and crack dynamics of vertisol soils

Submitted to: Trade Journal Publication
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 17, 2012
Publication Date: June 22, 2012
Citation: Dinka, R., Lascano, R.J. 2012. Challenges and limitations in studying the shrink-swell and crack dynamics of vertisol soils. Open Journal of Soil Science. 2(2):82-90.

Interpretive Summary: Soils with a clay content of 30% or more that have deep, wide cracks for some time during the year and have slickenslides, i.e., cracks in soils with swelling clays,are classified as Vertisols. These soils cover more than 700 million acres and about 6% of this area is within the US. These soils swell when wet and shrink when dry forming cracks. These cracks affect the hydrology of these soils and impact movement of water and nutrients. The formation of these cracks due to shrinking and swelling make the study of these soils difficult, particularly when defining crack geometry. In this paper, we review the current state-of-the art of methods that are available to quantify the geometry of soil cracks and their impact on the movement of water and nutrients. Properties that need to be measured include crack area density (number of cracks per square foot), depth and orientation of the cracks, and opening and closing of cracks. In this paper we give a comprehensive review of methods that are available and we discuss their use and limitations. A method that is widely used is knownas COLE, which stands for “Coefficient of Linear Extensibility” and gives an index of the shrink-swell potential of the soil in relation to its soil water content. This index is valuable but does not account for changes with time. We conclude that a combination of field and laboratory techniques to measure soil cracks and using this information on mechanistic models of hydrology will provide the necessary information to learn more about the spatial and temporal dynamics of soil cracks and their formation.

Technical Abstract: The need to study the shrink-swell and crack properties of vertic soils has long been recognized given their dynamics in time and space, which modifies the physical properties that impact water and air movement in the soil, flow of water into the subsoil and ground water, and generally alter the hydrology of vertic soils. Measurement of crack properties has been made by numerous researchers with the purpose to understand and quantify the spatial and temporal dynamics of shrinking and swelling and the associated formation of cracks. These crack properties, which are important in modifying hydrology of soils are: width, length, depth and orientation of soil’s cracks. To better understand the hydrology of vertic soils and incorporate crack properties into hydrologic simulation models, several techniques have been developed to measure crack properties. However, little attention is given to evaluate both the advantages and the limitations associated with these techniques. Thus, the purpose of this review is to highlight challenges and limitations that have been used or might be used to measure cracking in vertic soils.