Atrazine: Cheap herbicide, costly pollutant
By Kaitlin Morgan
K-State Research and Extension
For the past 50 years, atrazine has been used by corn and sorghum producers as an alternative to conventional tillage production practices for selective control of broadleaf and grass weeds.
While it is one of the most effective and economical herbicides available, atrazine’s chemical properties make it susceptible to runoff into surface waters. K-State researchers have found annual atrazine runoff losses of 1 to 3 percent of the total rate applied.
The spring and early summer corn and sorghum planting periods are when the highest concentrations of atrazine are present in surface waters. The concentrations of atrazine present in the surface waters during this period may rise above the drinking water and the aquatic life standards set for atrazine set by the Environmental Protection Agency.
Atrazine runoff becomes costly.
Ron Graber, a K-State Research and Extension watershed specialist, explained that atrazine runoff is mostly a surface water issue and has become a concern for two reasons:
Atrazine is an herbicide. When found in surface waters, it has the potential to become a health concern, and the cost to remove it from public drinking water is high.
High atrazine surface water concentrations indicate that the herbicide is leaving the field and not doing its job, which is to stay in place and kill weeds.
“We’re talking real dollars,” Graber said. “If producers use a chemical in a manner in which they lose significant amounts to runoff, they will begin to see less weed control and most likely it will translate into lower yields, less productivity and less profitability.”
Management is key.
Over the past 10 years, Graber and other members of the Little Arkansas River Watershed Restoration and Protection Strategies team have conducted education efforts to reach local producers through an incentive program and help them learn how to use best management practices to minimize atrazine runoff.
“When these best management practices are selected to fit each unique operation’s management system, they will minimize atrazine runoff in varying efficiencies. The producers are awarded incentives based on the predicted amount of runoff reduction for the different management practices they adopt,” Graber said.
According to Graber, the program has a high rate of acceptability and consistently documents water quality improvements; in some years the runoff reduction has been as high as 60 percent.
Proper management or governmental regulation?
“If we do not manage atrazine in a way that prevents runoff or significantly reduces it, then we could lose our ability to use it,” said Graber.
In the past decade, concern has sparked over the threat of a governmental atrazine ban in the U.S. similar to that seen in Europe.
Curtis Thompson, a K-State Research and Extension weed specialist, believes that if U.S. atrazine use was banned, corn producers would suffer and become less profitable. While Round-Up Ready corn protects against most pests, atrazine is crucial to managing glyphosate-resistant weeds.
However, there is no such thing as Round-Up Ready grain sorghum and Thompson believes, “a ban of atrazine is likely to destroy the sorghum industry.”
Graber agrees, saying that this threat is one reason why corn and sorghum growers are concerned with management practices. If they aren’t they should be, he said.
Importance of atrazine to sorghum producers
According to the U.S. Department of Agriculture, Kansas is the No. 1 state in sorghum production, producing 165 million bushels of grain sorghum in 2013.
Sorghum is used in livestock feed, ethanol production, gluten-free food products and is key to the value added grain supply chain.
Sarah Bowser, regional director for the Sorghum Checkoff, said that grain companies, local agriculture retailers, bankers and numerous other Kansas businesses would be impacted if sorghum production decreased.
“Sorghum farmers have limited weed control options,” Bowser said. “They are committed to stewardship and control weeds to preserve precious water and nutrients for the crop. Having weed control tools like atrazine is essential for producers using environmentally friendly conservation tillage or no-till farming practices.”
K-State Research and Extension weed specialist Randall Currie said that in the drought stricken western third of Kansas, summer-fallow agriculture is key for dryland production because it takes rainfall from more than one year’s time and stores it in the soil to grow a crop.
Currie said this requires that nothing be grown on the land for at least four to 11 months while the soil restores its moisture. The most economical way to achieve this is by substituting persistent, long lasting herbicides for tillage. As a lost-cost per acre option, atrazine serves as the backbone to many of these no-till operations.
“If this herbicide were removed from the market, tillage would be a very poor substitute,” Currie said. “We would have dust storms that rivaled the 1930s, when dust from the western United States blew all the way to our nation’s capital. This amount of soil loss was both an economical and an ecological disaster that did and could again cause permanent damage to the soil.”
At the present time, sorghum producers do not have an alternative to atrazine that is economical and effective so until one is found, Graber said producers need to properly manage their atrazine use.
More information about the 12 best management practices developed for minimizing atrazine runoff can be found in the publication, “Managing to Minimize Atrazine Runoff,” available online at www.ksre.ksu.edu/bookstore/pubs/mf2208.pdf.