Coarse textured materials have better strength and bearing resistance. They also are less susceptible to expansion and contraction with freezing and thawing and wetting and drying cycles. This is due to the plate-like nature of clays and their ability to attract each other and layers of water. Plasticity varies with water content. Agricultural soils should not be plowed above this limit.
Plasticity index is the difference between the plastic and liquid limits.
It is the range of moisture contents over which the soil is plastic. Soils with a high plasticity index are difficult to handle and unstable for bearing loads. Color directly affects the absorption of solar radiation and therefore is a factor in determining soil temperature. Color is indirectly related to other soil properties and can provide information subsoil drainage, organic matter content of surface horizons, and bulk density. Distinguishing soil horizons.