The shape of soil units (peds) that occur naturally in a soil horizon. Some possible soil structures are granular, blocky, prismatic, columnar, or platy. Soils can also be structureless if they don't form into peds. In this case they may be a consolidated mass (massive) or stay as individual particles (single-grained).
Refers to the arrangement of soil particles and the pore spaces between them. The mineral or inorganic part of soil consists of particles of different sizes. Between the soil particles are spaces, called pores. Their number and size strongly influence soil structure. Pores are important in allowing air and water to penetrate the soil. Small pores enable the soil to hold greater amounts of water; larger ones allow for faster drainage. Good soil needs many pores, varying in size with some holding air and some water. Loss of pores changes soil structure for the worse as far as plant growth is concerned.
How the particles that make up a soil are organized and clumped together. See also soil permeability, soil texture.