Percent of Air in Different Types of Soil

Effects of Soil Types

• Soil particles are classified by size: sand particles are the largest, silts are an intermediate size, and clays are the smallest. Generally, soils with larger particles have more pore space, and thus a greater percentage of air. (references 4)

Effects of Water

• Soil pore space contains both air and water. The total amount of pore space doesn't change, but after rain, pore space will have a higher percentage of water in relation to air. Once the soil dries out, the percentage of air will rise.

Ideal Conditions

• Soil pore space typically ranges between 35 and 55 percent. An ideal soil for plant growth is about 50 percent pore space, with 25% of the pore space being filled with air and 25 percent with water. Loam soils--those composed of a mixture of sand, silt and clay--are often best for maintaining this balance.