What is leaching?

• A. Upward movement of nutrients through soil
• B. Movement of water to groundwater
• C. Lateral movement of nutrients along the soil surface
• D. Downward movement of dissolved nutrients through soil

Answer: (D)

Leaching is the downward movement of dissolved nutrients through the soil with percolating water. When rain or irrigation infiltrates, water moves down the soil profile and carries soluble nutrients—like nitrate and other minerals—with it. This can deplete nutrients from the surface layer where roots are active and deposit them deeper in the soil or even into groundwater if the flow is strong. Leaching is driven by water movement through the soil and is influenced by soil texture, structure, and moisture. It differs from upward movement, which would bring water or solutes toward the surface, and from surface runoff, which moves water and nutrients laterally across the soil rather than downward.