MDARD Michigan Core Pesticide Applicator Practice Exam

Which soil characteristics enhance the likelihood of pesticide leaching?

1. Very fine and deep

2. Very coarse and shallow

3. Clayey and moist

4. Sandy and heavily mulched

The correct answer is: Very coarse and shallow

The choice indicating that very coarse and shallow soil enhances the likelihood of pesticide leaching is based on key characteristics of soil composition and structure. Coarse soils, such as sandy soils, have larger particle sizes and greater spaces between those particles. This structure allows water to move through the soil more quickly, facilitating the downward flow of both water and any soluble pesticides mixed into the soil. Shallow soils pose an additional concern because they do not have a significant depth to hold moisture or pesticides. When rainfall occurs, or when irrigation practices are used, the rapid water movement in shallow, coarse soils can easily carry pesticides beyond the root zone of plants into deeper layers of soil or even into groundwater. In contrast, very fine soils, clayey soils, or heavily mulched sandy soils tend to retain water and hold onto pesticides more effectively, reducing the risk of leaching. Fine-grained soils have smaller pore spaces that slow down water movement. Clayey soils, while retaining moisture well, also have a higher potential for holding onto chemicals due to their small particles and surface properties. Meanwhile, heavy mulch acts as a barrier to water movement, further decreasing leaching potential.