What is leaching?

Leaching refers specifically to the process of a substance, such as a pesticide, moving down through the soil profile. This occurs when water – usually from rainfall or irrigation – percolates through the soil layers, carrying with it dissolved substances. As the water moves downward, it can transport pesticides with it, potentially reaching groundwater.

This movement is significant because it allows for the assessment of how pesticides can affect water quality, particularly when they leach into aquifers or other water sources. Understanding leaching is crucial for applicators as they determine how to apply pesticides in a way that minimizes environmental impact.

The other options highlight different processes related to pesticide management. The movement of pesticide across the soil surface describes surface runoff, while evaporation pertains to the loss of volatile components into the air. Transformation in soil refers to the biodegradation or chemical changes that pesticides undergo but does not involve their movement through the soil. Each of these processes plays a role in the fate of pesticides in the environment, but leaching is specifically concerned with the downward movement through soil.