Oregon Pesticide Practice Test

Pesticides are more likely to leach through which type of soil?

1. Sandy soil, low in organic matter

2. Clay soil, high in organic matter

3. Silt soil, well-drained

4. Loamy soil, evenly balanced

The correct answer is: Sandy soil, low in organic matter

Sandy soil, particularly when low in organic matter, has larger particles and greater spaces between those particles. This results in higher permeability and lower water retention compared to other soil types. When pesticides are applied to sandy soil, they can move through it more easily and deeper into the ground, increasing the likelihood of leaching. In contrast, clay soil is dense with small particles, holding water and nutrients more effectively, thus reducing the potential for leaching. Silt soil can have moderate retention capabilities, while loamy soil, which is a balanced mix of sand, silt, and clay, also exhibits less leaching than sandy soil due to better water-holding properties. Therefore, sandy soil with low organic matter creates conditions that are more favorable for pesticide leaching.