Which of the following soil types have a high capillarity?

Analyze the question: Capillarity is the ability of soil to draw water upward through its tiny spaces (pores) between particles. It depends on the size of those pores.

Explain the concept:

• Capillarity is high when soil particles are very small, because the pores are narrow. Narrow pores pull water up strongly through adhesion and cohesion.
• Capillarity is low when soil particles are large, because the pores are wide and water drains straight down instead of rising.

Compare the soil types:

• Sand: Large particles and big pores. It has high drainage and low capillarity.
• Clay: Very fine particles and very narrow pores. It has high capillarity, though water moves slowly.
• Silt: Fine particles, smaller than sand and larger than clay. It has high capillarity.
• Loam: A mixture of sand, silt and clay. It has moderate capillarity.

Check the options:

• A. Sand and clay: sand has low capillarity, so this is wrong.
• B. Loam and sand: sand has low capillarity, so this is wrong.
• C. Silt and sand: sand has low capillarity, so this is wrong.
• D. Silt and clay: both have fine particles and narrow pores, so both have high capillarity. This is correct.

Tip: Remember "small particles, small pores, high capillarity." Sand is the odd one out because it has coarse particles. Any option containing sand is wrong when the question asks about high capillarity. You can use this to eliminate A, B and C quickly.