Relationship of Air and Water in the Soil Soil provides a foundation for tree growth-structurally and biologically. Soil supports a tree's physical weight and resists the forces of wind. Soil al supplies water, air, and nutrients. The value of the soil as structural and biological support is related to soil structure. Soil structure influences plant growth, because it affects moisture, aeration, heat transfer, and the mechanical resistance to root growth.
Most people think of soil as being a mixture of solid elements, such as minerals and organic matter.
But, open spaces in soil, called pores, are equally important. The size and distribution of soil pores affect the movement and availability of moisture and air through the soil. The air-water relationship is a critical one for optimum plant growth. The number of pore spaces must be adequate and the variety of sizes appropriate. Pore size determines the relative amounts of air and water that soil will hold.