MDARD Michigan Core Pesticide Applicator Practice Exam

Which of the following is true regarding the leaching of pesticides through soil?

1. Sandy soil, high in organic matter is most likely to leach pesticides

2. Heavy clay soil minimizes leaching of pesticides

3. Sandy soil, low in organic matter is more likely to leach pesticides

4. Leaching only occurs during heavy rainfalls

The correct answer is: Sandy soil, low in organic matter is more likely to leach pesticides

The assertion that sandy soil with low organic matter is more likely to leach pesticides is accurate because of several key characteristics of sandy soils. Sandy soils have larger particle sizes and greater pore spaces, which facilitate rapid water movement. This means that when precipitation occurs or irrigation takes place, water moves quickly through these soils and can carry pesticides along with it, leading to increased leaching. Additionally, organic matter plays a crucial role in nutrient and pesticide retention in soils. Soils high in organic matter can hold onto pesticides more effectively, reducing their movement through the soil profile. In contrast, sandy soils lacking this organic material have less capacity to retain chemical substances, contributing to a higher risk of leaching. Heavy clay soils are characterized by finer particles and smaller pore spaces, leading to slower water movement, which helps to minimize leaching. The concept that leaching only occurs during heavy rainfalls is misleading, as leaching can happen at varying rates during normal precipitation or irrigation events, especially in soils that are more permeable, like sandy soils.