Corn and sorghum growers are making the case that newly proposed restrictions on atrazine use will lead to their practicing less conservation tillage, resulting in reduced carbon sequestration at a time American agriculture is trying to make inroads in the fight against climate change.

On June 30, the Environmental Protection Agency issued proposed revisions to its 2020 interim decision that would require growers of field corn, sweet corn and sorghum to implement conservation practices on their fields in order to continue applying the widely used herbicide. Sugarcane growers would not have to implement any practices, but would be subject to a limit of eight pounds of active ingredient a year in Florida and four pounds a year in Louisiana.

The nature and number of practices implemented would vary depending on the level of atrazine in the grower’s watershed. In proposed revisions to its previous interim registration review decision, EPA rejected the Trump administration’s proposal to increase what’s called the Concentration Equivalent – Level of Concern (CE-LOC) for the herbicide in watersheds to 15 parts per billion.

A re-evaluation of that level, used as the trigger for regulation, concluded it “was not adequately supported by science,” the agency’s proposed revisions document said, keeping the level at 3.4 parts per billion. EPA conducted the new analysis in response to a court challenge brought by environmental groups.

The result is a detailed set of requirements designed to protect aquatic plants in watersheds with atrazine levels above 3.4 ppb and, by extension, other aspects of the environment.

“The focus on toxicity to aquatic plant communities is necessary to ensure that the atrazine concentrations in watersheds do not cause significant changes in plant community structure, function and productivity and thus put at risk the food chain (e.g., reducing food for fish, invertebrates, and birds) and ecosystem integrity (e.g., erosion control and animal habitat),” EPA said.

Chris EdgingtonNCGA President Chris Edgington

But corn and sorghum growers, along with atrazine maker Syngenta, plan to push back against the proposed changes, contending that the 3.4 ppb CE-LOC is not scientifically justified and will result in a reduction in conservation tillage.

“There's no question that when you take a tool out of the toolbox that farmers have had for over 60 years, and provides a very nice synergistic benefit when it's combined with other chemicals so that you don't have to run full rates on things, you're going to have to do a couple of things,” said National Corn Growers Association President Chris Edgington.

One of those things is using more of a different product “to get the same control,” he said. The other thing growers might have to do is till their fields to control weeds, which means less carbon sequestered in the soil and more potential for runoff.

John Duff, executive vice president of the National Sorghum Producers, echoed Edgington’s comments. Some type of conservation tillage is practiced on three of every four acres of sorghum in the U.S., which is “only possible because we have tools like atrazine. If you take those chemicals off the market, we will have to go back to the tilling, there's just no way around it.”

The American Sugar Alliance is pulling together technical comments from growers and companies about the impact of EPA’s proposal, “so, we do not have an industry-wide response to share at this point,” said Rob Johansson, director of economics & policy analysis at ASA.

Syngenta, in a document posted on July 7, said “further atrazine usage reductions based on this significantly lowered LOC will contribute to grower decisions that will result in more tillage, increased soil disturbance, and fewer conservation practices that benefit climate-smart agricultural outcomes.”

The requirements could affect 65 million acres of corn, sorghum and sugarcane, the company said. In total, about 97 million acres of the three crops are grown in the U.S.

Duff also said a return to tillage would significantly increase fuel use.

NSP and NCGA plan to rally their members to put pressure on EPA as it moves ahead with its registration decision. A 60-day comment period closes in early September, and EPA has promised an external peer review “of the risks to the aquatic plant community that underlies [its] proposed risk management strategy.”

The strategy includes “pick-lists” of conservation practices that growers would choose to implement depending on the level of atrazine estimated to be present in their watershed.

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EPA would require sorghum, field corn and sweet corn growers in watersheds with atrazine levels above 3.4 ppb, which makes up about 18% of all watersheds in the U.S., to choose from practices that include cover crops, contour buffer strips, terrace farming or field borders, depending on the crop. (Sweet corn has five pick-list practices, and sorghum and field corn each have twelve.) The annual limit for atrazine use would be two pounds per acre. 

EPA is also “proposing options through a pick-list format to allow higher rates in Southern field corn production,” and is proposing an annual limit of eight pounds per year for sugarcane production in Florida, and four pounds per year in Louisiana and Texas (with no pick-list requirements).

Nathan Donley, environmental health science director at the Center for Biological Diversity, called the industry’s criticisms of EPA’s approach a “last-ditch effort to use scare tactics to prevent commonsense regulation.”

Donley noted that some growers may opt not to make pre-emergent applications of atrazine since that is one of the pick-list options allowing growers to continue to use the product.

Nathan DonleyNathan Donley, CBD

However, he adds, “the idea that everyone would switch to tillage is ridiculous. Most farmers would just switch to a different pre-emergent herbicide, of which there are many. And most importantly, stopping pre-emergent atrazine applications is one of 13 conservation practices that farmers can pick from in mitigating their part in environmental contamination of atrazine.”

Most of the other conservation practices “have carbon-capture benefits, like cover cropping and maintaining a vegetative filter strip (which would presumably have vegetation on it year-round instead of just during the growing season). “Considering the variety of options growers have now, there will almost certainly be climate benefits to implementing this plan. And that is on top of reducing the use of atrazine, which is very carbon-intensive to manufacture and distribute.”

But not all practices work in all terrains, according to weed scientists and extension agents surveyed by USDA’s Office of Pest Management Policy.

“Many of the proposed practices would be feasible for field corn producers in the Corn Belt, and also those utilizing irrigation in the southern Plains,” according to a synthesis of those comments compiled by OPMP and posted in the regulatory docket.

“On the other hand, for ‘dry land’ field corn producers (i.e., growing without any supplemental irrigation) in the Southern Plains and other arid regions of the U.S., the proposed practices would be relatively infeasible,” the OPMP document said.

Duff said it will be important to craft solutions that work for growers wherever they farm.

He called the pick-list approach “a good step” overall.

“There's going to be a lot of opportunity to work with EPA on a pick-list that works for specific crops in specific areas,” he says. “Not all areas are created equal, and there are things on the pick-list that work in one area, but may not work in another. And so it's going to be important to make sure that all areas have an equal number of options on the pick-list, so a producer in a flat area doesn't have more options to mitigate than a producer in a rolling area.” 

Edgington singled out a proposed requirement that would prohibit applications if a “storm event… is forecasted to occur within 48 hours following application.”

“I don't know how good your weather people are,” he said. “I can tell you that they try very hard out here in the Midwest, but they're not that accurate.”

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