Leaching is necessary to move the herbicide into which zone?

• A. Surface soil
• B. Root zone
• C. Leaf tissue
• D. Water column

Answer: (B)

Leaching is the downward movement of dissolved herbicide through the soil with infiltrating water. After application, rain or irrigation can push the chemical from the surface down into the soil profile where plant roots reside. The root zone is where roots absorb water and nutrients, so it’s the zone most affected by leaching and where the herbicide can impact plants or move beyond the target site. Leaf tissue uptake happens via foliar exposure, not soil leaching, so it isn’t the zone reached by this process. The surface soil stays near the top and may or may not be reached depending on depth and soil conditions, while the water column becomes involved only if the chemical continues moving beyond the root zone into groundwater or surface water.