Avoiding Glyphosate and Atrazine Runoff and Groundwater Contamination

Avoiding Glyphosate and Atrazine Runoff and Groundwater Contamination

June 19, 2009
This week's storms came just as some producers were able to get back in the field to make delayed herbicide applications. With the threat of heavy downpours looming, it can be hard to pick the right time to get the job done while avoiding the potential for pesticide runoff.

Adopting a two-pronged strategy that includes using best management practices for herbicide applications and conservation measures to slow and reduce runoff helps you avoid contamination, whatever the weather. Preventing pesticide runoff into waterways is of utmost importance to avoid contamination of our drinking water. In addition, pesticide that moves from the target site can't do what it was intended, resulting in reduced weed control and wasted resources.

Problems Associated with Pesticide Run-off

Atrazine runoff has been a concern for many years and in 1993, atrazine use was restricted. It is estimated that 76.4 million pounds of atrazine is applied annually, of which 86% is applied to corn. In addition, glyphosate has become a concern in recent years as its use has increased. Since 1997 glyphosate use has tripled due to widespread use of Roundup Ready crops.

Water contamination by atrazine and glyphosate can occur from misapplication or through storm water runoff. It is of particular concern due to health effects documented by the EPA.

  • Short- and long-term exposure to atrazine can cause congestion of the heart, lungs and kidneys, weight loss, and muscle degeneration.
  • Short- and long-term exposure to glyphosate can cause congestion of the lungs, kidney damage, and reproductive effects.

Once atrazine or glyphosate enter the water source, they have a direct path to our drinking water.

The United States Geological Survey (USGS) has conducted a survey of streams in the Midwest to determine the presence of various herbicides, including atrazine and glyphosate.

  • Glyphosate was detected in 36% of the samples and a degradation product of glyphosate (aminomethylphosphonic acid) was found in 69%.
  • Atrazine was detected in 30% of the water samples at or above the allowable limit. In general, the atrazine concentrations were lower than those found in similar USGS surveys conducted in the 1990s.

Steps for Avoiding Pesticide Run-off

Using best management practices for herbicide applications and conservation measures can limit the amount of pesticides such as atrazine and glyphosate in storm water runoff. Intensity of rainfall varies greatly from storm to storm, so plan for the effects of runoff in the worst conditions and use best management practices to prevent it.

Land Management

  • Identify water bodies vulnerable to contamination such as streams, wells, lakes, ponds or other waterways adjacent to pesticide application areas and, where possible, place buffer strips in sensitive areas to capture pesticide-contaminated runoff.
  • Create terraces and plant grass in waterways to slow water flow and the movement of pesticides to larger water bodies.

Best Application Practices

  • Always follow pesticide label instructions and use the best pesticide for the job. Unless the label recommends it, such as with some pre-emergent herbicides, don't apply pesticide if rain is forecast to occur within 24 hours.
  • Store pesticides away from water sources and in locations that won't be easily flooded after rainfall. Make sure these facilities are in good repair and do not leak.
  • Always mix and load pesticides at least 50 feet away from all water sources. Use a mixing and loading pad made of impermeable material and with walls on all sides to prevent pesticides from spilling onto non-target areas where they can soak into soil or be carried away by runoff.
  • Properly dispose of any pesticides not applied. Apply leftover rinsate onto labeled target sites and away from water.


For more information visit the following Web sites:

Leah Sandall
Extension Assistant
Erin Bauer
Extension Assistant
Clyde Ogg
Pesticide Safety Educator

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