Plastic properties

Application of a force to soil can result in an elastic, non-permanent, deformation that only lasts while the force is applied or a plastic, permanent deformation that persists after the load is removed. The latter may, or may not result in a decrease in the soil volume. How easily and how much the volume changes is determined by the soil's plasticity. It is an important factor influencing ease and outcome of soil tillage operations. Soil plasticity is caused by the lubricating film of water surrounding soil particles that allow the soil to change shape without rupturing upon application of forces. As an inherent soil property it is governed primarily by the surface area of the soil particles. Plasticity increases with increasing clay content, activity of clay minerals, position of the adsorbed cations in the lyotropic series and organic matter content