Oklahoma Applicators License Core Practice Exam

Which type of soil is likely to slow pesticide movement into groundwater?

1. Sandy soil

2. Coarse soil

3. Fine-textured soil with organic matter

4. Clay soil only

The correct answer is: Fine-textured soil with organic matter

Fine-textured soil with organic matter is effective in slowing pesticide movement into groundwater due to its physical and chemical properties. The fine texture of this soil type creates smaller pore spaces, which limits the flow of water and, consequently, the movement of pesticides. Additionally, organic matter has the ability to adsorb chemicals, binding them to the soil particles and reducing their mobility. This adsorption is crucial because it not only slows down the transportation of pesticides through the soil profile but also decreases the likelihood of these substances reaching groundwater supplies. In contrast, other soil types like sandy and coarse soils have larger particles and greater pore spaces that allow for faster water movement, which can lead to quicker pesticide leaching into groundwater. Clay soils, while they can also slow movement due to their fine texture, may not necessarily have the beneficial organic matter that enhances the binding and retention of pesticides. Therefore, fine-textured soil with organic matter presents the most effective barrier against the rapid movement of pesticides into groundwater.