Generally speaking, soil is approximately 50% air plus water.

Generally speaking, soil is approximately 50% air plus water.

• A. True
• B. False
• C. 25%
• D. 60%

Answer: (A)

The concept here is porosity—the fraction of soil volume that is open space between the solid particles. In many soils, about half of the soil’s volume is pore space. That space is filled with air when the soil is dry and with water when it’s moist. So saying soil is roughly 50% air plus water reflects this common rule of thumb: roughly half the volume is not solid material, just open space that can be occupied by air or water. Exact numbers vary with soil texture, structure, and moisture, but 50% pore space is a good general estimate.

The concept here is porosity—the fraction of soil volume that is open space between the solid particles. In many soils, about half of the soil’s volume is pore space. That space is filled with air when the soil is dry and with water when it’s moist. So saying soil is roughly 50% air plus water reflects this common rule of thumb: roughly half the volume is not solid material, just open space that can be occupied by air or water. Exact numbers vary with soil texture, structure, and moisture, but 50% pore space is a good general estimate.