Leaching Due to Pesticides

Pesticide Leaching

• Leaching occurs when a pesticide moves through soil. The chemical properties of the pesticide in question play a significant role in the likelihood of that pesticide to leach; for instance, the tighter a pesticide's molecules bind to soil particles, the less likely it is to leach. The properties of the soil over which the pesticide is applied also plays a role. Soil permeability determines how easily water can move through soil, and pesticides very often make their way through soil by traveling with water.

Consequences

• If pesticide-contaminated water makes its way to groundwater deep in the soil, it can contaminate human and animal water supplies. Pesticide leaching can also contribute to reduce the effectiveness of the pesticide in controlling the pest and can injure "non-target" species of plants and animals.

Avoiding Pesticide Leaching

• The most important way to avoid pesticide leaching is to always follow the manufacturer's application instructions, particularly dosage and application instructions. If a pesticide's labeling advises you to not water target plants after application, do not water target plants under any circumstances, since irrigation often contributes to pesticide leaching. As much as is possible, avoid using any pesticides that are highly water soluble, not readily adsorbed and not rapidly degraded.

Other Considerations

• By far, the most common cause of pesticide leaching is improper use, particularly during the application process. But under certain circumstances, leaching can occur for reasons other than human error. Any mixing, storage or application equipment that is damaged can allow pesticides to leach out. Even given the right combination of soil conditions, pesticides can leach into soil when applied exactly according to the manufacturer's directions. But simply using the pesticide properly is still by far the most effective way of preventing leaching problems.