Landscape plants perform best in soils that contain pore spaces that allow water, air and roots to move freely deep into the soil. Ideal soil structure consists of 50% particulate matter, 25% available pore space for water, and 25% available pore space for air. The size and arrangement of various soil particles as well as the presence of organic matter and microorganisms are key factors in balanced soils and healthy roots. In many regions, soil types have been disturbed and compacted so that air and water movement is greatly reduced if not diminished.