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Competency Area 7: Using Pesticides in an Environmentally Sound Manner

PO 42. Understand soil/pesticide interactions and their influence on pesticide selection, pesticide use, and water quality protection. Be aware of pesticide runoff/leaching potential predicting tools such as Win-PST 3 and be able to recommend mitigation to improve or minimize the negative effects on the environment.

In addition to the potential for transport to surface or groundwater, a pesticide needs to be evaluated for its toxicity once it has reached reach groundwater need to be evaluated for their risk to human health. The U.S. Environmental Protection Agency has issued guidelines for lifetime health advisory levels (HAL's) for commonly used pesticides, which includes a margin of safety to protect humans. Water containing pesticides in concentrations at or below this level is believed to be acceptable for drinking every day over the course of a lifetime. HAL's are typically expressed in concentrations of micrograms per liter, which is equivalent to parts per billion (ppb).

As discussed above, the movement of pesticides in soil depends on pesticide characteristics, including half-life, solubility, and adsorption coefficient, and on soil characteristics, including organic matter content, texture, and permeability. The interaction of pesticide and soil properties defines the potential for a pesticide to reach surface or groundwater.

Computer models can be applied to simulate movement of chemicals over the soil surface and through the soil profile. These models have the potential to integrate physical processes and to depict the interaction of soil and pesticide properties. They are therefore useful tools for estimating pollution potentials.

*This information was adapted from “Pesticide Management for Water Quality; Principles and Practices” Van Es, HM and Trautmann, NM. 1990. See for more detailed information.


The USDA-NRCS National Water and Climate Center developed and supports the Windows Pesticide Screening Tool (WIN-PST). WIN-PST is a pesticide environmental risk screening tool that NRCS field office conservationists, extension agents, crop consultants, pesticide dealers and producers can use to evaluate the potential for pesticides to move with water and eroded soil/organic matter and affect non-target organisms. For more information on Win-PST 3, see
Note: WIN-PST 3.0 has been superseded by WIN-PST 3.1