What can cause pesticides to leach through the soil?

Pesticides can leach through the soil due to multiple factors, making the option indicating all of them the most comprehensive answer.

Soil type plays a significant role in pesticide movement because different types of soil have varying particle sizes, textures, and structures that affect how water and chemicals permeate. Sandy soils, for example, allow for quicker drainage and may lead to increased leaching, while clay soils have smaller particles that may retain more water and pesticides.

Application timing is another critical factor. If pesticides are applied before heavy rainfall or irrigation, there is a higher likelihood that they will wash away from the application site and leach into the groundwater. Conversely, applying during dry conditions may minimize leaching.

Bacterial activity in the soil can also influence pesticide degradation and mobility. Bacteria can break down certain pesticides, potentially leading to their movement through the soil profile. The interaction between biological activity and pesticide chemistry can affect how long a pesticide remains active in the soil and whether it leaches.

Thus, all of these factors—soil type, application timing, and bacterial activity—contribute to the potential for leaching, making the choice that includes all of them the correct answer.