QAL Laws & Regulation Practice Exam

In which soil conditions are pesticides more likely to leach through the soil?

1. Clay soil with high organic matter

2. Sandy soil with low organic matter and shallow groundwater

3. Dense soil with heavy rainfall

4. Loamy soil with good drainage

The correct answer is: Sandy soil with low organic matter and shallow groundwater

Pesticides are more likely to leach through the soil in sandy soil with low organic matter and shallow groundwater conditions. Sandy soil has larger particle sizes compared to clay or loamy soils, which allows water to flow more rapidly through it, facilitating the movement of pesticides deeper into the soil profile. When organic matter is low, there’s also less capacity for the soil to bind to the pesticides, leading to increased mobility and a higher likelihood of leaching. Additionally, shallow groundwater means that there is a shorter distance for the pesticides to travel before reaching the water table, making it easier for them to contaminate groundwater sources. This combination of soil type and organic matter content plays a critical role in the potential for pesticide leaching, as adequate binding sites found in soils with higher organic matter can substantially reduce this risk.