Soil permeability refers to

Step 1: Analyze the question The question asks for the definition of soil permeability. The key word is "permeability," which comes from "permeate," meaning to pass through.

Step 2: Explain the concept Soil permeability is the ability of the soil to let water (and air) pass through its pores. It depends mainly on particle size and pore spaces:

• Sandy soil has large particles and large pore spaces, so it is highly permeable. Water drains quickly.
• Clay soil has very fine particles and tiny pores, so it has low permeability. Water drains slowly and may waterlog.
• Loamy soil is moderately permeable, which is why it is best for farming.

Step 3: Evaluate each option

• A. How easily water passes through the soil. Correct. This is the definition of permeability, the rate at which water moves downward through the soil.
• B. The proportion of air in the soil. This describes soil aeration or porosity, not permeability.
• C. The proportion of water the soil holds. This describes water retention or water-holding capacity, or soil moisture content.
• D. How well water rises up the soil. This describes capillarity, the upward movement of water through soil pores.

Step 4: Answer The correct option is A.

Step 5: Exam tip Link each soil term to its keyword:

• Permeability = pass through (drainage)
• Capillarity = rise up
• Porosity/aeration = air spaces
• Water retention = holds water

Remember: sand drains fast (high permeability), while clay holds water (low permeability).