Which of the following factors most affects the movement of pesticides into groundwater?

The movement of pesticides into groundwater is primarily influenced by pesticide placement, persistence, and frequency of application. This is because the way a pesticide is applied can significantly determine how much of it penetrates the soil and reaches the water table.

When a pesticide is placed directly onto the vegetative target areas and not overused, the likelihood of runoff is reduced. Conversely, if pesticides are applied frequently and excessively, or if they are highly persistent in the environment, they have a greater chance of leaching into the groundwater. Persistence refers to how long a pesticide remains active in the environment before it breaks down, which can impact how long it can potentially migrate through the soil layers.

While the type of pesticide and storage conditions contribute to overall risk and efficacy, they do not directly dictate the transport process into groundwater as significantly as placement and application practices do. Additionally, watering habits may influence surface runoff but are less directly correlated with groundwater contamination compared to application techniques.