Columnar and prismatic large peds with considerable vertical extent, common in dry regions where little moisture percolates downward and few roots reach the lower layers of the soil; columnar peds have rounded tops; prismatic peds are more angular.
Platy thin flat peds with considerable horizontal extent; common in areas where soil processes produce distinct layered accumulations of clay or minerals in a soil, such as the calcium layers of the Great Plains or the iron layers in New England; platy peds tend to resist upward or downward flow of water.
Massive a structure less soil in which the particles all seem to stick to each other; most common in poorly drained soils where roots are few and water movement is slow; massive layers are often nearly impermeable.
Soils are grouped into three general texture classifications – coarse, medium, and fine. Texture may best be defined as the “feel” of soil.
A coarse soil with a high percentage of sand particles will feel loose and grainy when dry and will fall apart when wet.
Medium-sized soil particles (silt) feel like talcum powder.
Fine soil texture is dominated by clay particles; clay soils crack when dry and stick together when wet.
The proportions of sand, silt, and clay determine the texture characteristics of soils and are commonly depicted on the soil triangle. A loam is a mixture containing a substantial proportion of each of the three grades. Loam soils provide the best substrate for plant growth.
Texture is important because it largely determines the ability of the soil to retain water or to transmit water to the intermediate belt below.