What happens during leaching of herbicides?

Leaching of herbicides occurs when these chemicals are washed away from the soil profile into deeper layers or into groundwater, primarily due to rainfall or irrigation. This process can lead to the movement of herbicides beyond their target areas, potentially affecting surrounding ecosystems or contaminating water sources. When heavy rainfall or excessive irrigation occurs, the water can carry the dissolved herbicides downward through the soil, where they may not only impact non-target plants but also contaminate groundwater supplies.

This understanding of leaching underscores the importance of proper herbicide application and timing to minimize environmental risks. The other options describe different processes that do not accurately represent leaching: absorption by plant roots pertains to plant uptake, breakdown refers to the degradation of herbicides into non-toxic forms, and stability within the soil would imply that the herbicides remain in place rather than moving through the soil layers.