Which soil component tends to hold pesticides longer, reducing leaching?

• A. Sand
• B. Water
• C. Clay or organic matter
• D. Air

Answer: (C)

Retention of pesticides in soil depends on adsorption to solid particles. Clay minerals and organic matter provide a large, highly active surface with many binding sites that attract and hold pesticides, especially those that are hydrophobic or carry certain charges. This attachment keeps pesticides from dissolving freely in water and moving downward with percolating moisture, so leaching is reduced. In contrast, sandy soils have fewer binding surfaces, so pesticides stay more in the moving water and leach deeper more readily. Water serves as the transport medium, not a retention site, and air is just pore space without the ability to hold pesticides. So, clay or organic matter tends to hold pesticides longer, decreasing leaching.