If the soil particles are greater than 2 mm they are not part of the soil texture and are considered gravel. The amount and kind of clay in a soil, influences the extent to which the soil shrinks as it dries out or swells as it gets wet. The shrink-swell potential refers to the relative change in volume to be expected of soil material with changes in moisture content. Shrinking and swelling of soils damages building foundations, roads, and other structures in places. Soils having a high shrink-swell potential are the most hazardous.
Clay soils have more nutrient and water storage than sandy soils.
Clay soils hold more water but the water is harder to move through it. Soil reaction is the degree of acidity or alkalinity of a soil expressed in pH values. A soil that tests to a pH 7.0 is neutral because it is neither acid nor alkaline. This can be measured as the relative ease of fluid flow. Permeability is measured within a depth of 60 inches.