The amount of air and water available to plant roots depends on soil texture (particle sizes) and structure (particle arrangement). Sandy soils have large pore spaces that contain large amounts of air; large spaces allow water to drain quickly, so the soil dries relatively fast. Clay soils have many small pore spaces that retain water, but much of this water is too tightly held to be available to roots. Small pore spaces drain poorly (slowly) and often provide insufficient space for oxygen needed by roots. Silt particles are intermediate in size between clay and sand. Loam soils have roughly equal proportions of sand, silt, and clay. Loam soils that are not compacted generally provide the best balance between water-holding ability and aeration. Credit: Adapted from an illustration by David Kidd
