Downward movement of a pesticide through the soil in water is called leaching.

• A. Runoff
• B. Leaching
• C. Precipitation
• D. Evaporation

Answer: (B)

Leaching is the downward transport of a pesticide through soil as water moves through the soil profile. When water from rainfall or irrigation infiltrates the ground, it can dissolve pesticide residues and carry them downward with the percolating water, potentially reaching deeper soil layers and even groundwater. This distinguishes leaching from other processes: runoff is water moving across the surface, precipitation is the rain itself, and evaporation is water turning into vapor and leaving the surface—none of those describe the vertical movement of dissolved pesticide through soil. The tendency for leaching depends on how soluble the pesticide is and how strongly it binds to soil particles; highly soluble pesticides or soils with little organic matter and rapid water movement are more prone to leaching, which is why timing and formulation choices matter to minimize this transport.