Leaching of pesticides into groundwater is more likely on which soil type?

• A. Sandy soil
• B. Clay soil
• C. Loamy soil with high organic matter
• D. Gravelly soil

Answer: (A)

Leaching into groundwater happens when water moving through soil carries dissolved pesticides and the soil doesn’t hold onto them. Sandy soils have large, open pores that let water drain quickly, and they typically have low organic matter and low adsorption of chemicals. Because there’s little to slow or retain the pesticide, it can move downward with percolating water more readily and reach groundwater. Clay soils, with many tiny pores and high adsorption, hold onto pesticides more and slow their movement; loamy soils rich in organic matter do even more to bind chemicals and promote degradation, further reducing leaching. Gravelly soils drain quickly as well, but the standout factor here is that sandy textures provide the least resistance to downward movement, making leaching most likely there.