Would banning atrazine benefit farmers?

Abstract

Atrazine, an herbicide used on most of the US corn (maize) crop, is the subject of ongoing controversy, with increasing documentation of its potentially harmful health and environmental impacts. Supporters of atrazine often claim that it is of great value to farmers; most recently, Syngenta, the producer of atrazine, sponsored an “Atrazine Benefits Team” (ABT) of researchers who released a set of five papers in 2011, reporting huge economic benefits from atrazine use in US agriculture. A critical review of the ABT papers shows that they have underestimated the growing problem of atrazine-resistant weeds, offered only a partial review of the effectiveness of alternative herbicides, and ignored the promising option of non-chemical weed management techniques.

In addition, the most complete economic analysis in the ABT papers implies that withdrawal of atrazine would lead to a decrease in corn yields of 4·4% and an increase in corn prices of 8·0%. The result would be an increase in corn growers’ revenues, equal to US$1·7 billion annually under ABT assumptions. Price impacts on consumers would be minimal: at current levels of ethanol production and use, gasoline prices would rise by no more than US$0·03 per gallon; beef prices would rise by an estimated US$0·01 for a 4-ounce hamburger and US$0·05 for an 8-ounce steak. Thus withdrawal of atrazine would boost farm revenues, while only changing consumer prices by pennies.

Keywords:

• Agriculture
• Atrazine
• Corn
• Economic impacts
• Herbicides
• Weed management

Notes

<?ENTCHAR ast?> Atrazine has been excluded from the re-registration process in the European Union since 2003 owing to the manufacturer’s inability to demonstrate that its use would not result in groundwater concentrations greater than 0·1 μg/l.⁶

<?ENTCHAR dagger?> See http://agsense.org/atrazine-alarmists/.

<?ENTCHAR Dagger?> We agree that Ackerman’s earlier work is dated in one respect: it emphasized that fact that Germany and Italy have continued to have high corn yields after ending the use of atrazine; newer information suggests that many European corn growers rely on a less well-known triazine herbicide that is chemically very similar, but not quite identical, to atrazine.

<?ENTCHAR sect?> Weed pressure data derived from Bridges’ data on infestation and yield reduction, Tables 2 and 8.¹³

<?ENTCHAR ast?><?ENTCHAR ast?> Acreage infested is derived from Bridges’ estimates of the percentage of crop acres containing a population of the weed, which, if left uncontrolled, would be sufficient to result in yield reduction. This percentage, for each agricultural region, was multiplied by the region’s total acres of corn to arrive at an approximate number of acres infested. The potential bushel loss was calculated from Bridges’ estimates of the average percent yield loss expected to occur in infested acreage if the specified weed was left uncontrolled, multiplied by the region’s average yield per acre and number of infested acres.

<?ENTCHAR dagger?><?ENTCHAR dagger?> Some species, such as pigweeds and waterhemp, are combined under their shared genus. Morningglories were not included owing to omission in the source document.

<?ENTCHAR Dagger?><?ENTCHAR Dagger?> Table data are for weeds in Iowa, the top corn-producing state, but the effectiveness of these herbicides is likely to be similar for other corn-producing states. Atrazine entries in the table assume no resistance to atrazine, which is a questionable assumption for foxtails, pigweeds and waterhemp, lambsquarters, and velvetleaf.

<?ENTCHAR sect?><?ENTCHAR sect?> Table data are for weeds in Iowa, the top corn-producing state, but the effectiveness of these herbicides is likely to be similar for other corn-producing states. Atrazine entries in the table assume no resistance to atrazine, which is a questionable assumption for foxtails, pigweeds and waterhemp, lambsquarters, and velvetleaf.

<?ENTCHAR ast?><?ENTCHAR ast?><?ENTCHAR ast?> Two herbicides applied at the same time, such as flumetsulam and clopyralid in Tables 2 and 3, are counted as one treatment in this discussion, in contrast to sequential applications of herbicides.

<?ENTCHAR dagger?><?ENTCHAR dagger?><?ENTCHAR dagger?> WeedSOFT was developed by weed scientists and is widely used in the Midwest. Several peer-reviewed articles have evaluated the accuracy of WeedSOFT’s predictions based on pooled data from numerous site-years and found that observed and predicted corn yield-loss values were similar.^20,21

<?ENTCHAR Dagger?><?ENTCHAR Dagger?><?ENTCHAR Dagger?> These weed species include most of the ten worst corn weed species nationally. The weed species analyzed were fall panicum, giant foxtail, common cocklebur, common ragweed, common sunflower, ALS resistant waterhemp, giant ragweed, hemp dogbane, pitted morningglory, and velvetleaf.

<?ENTCHAR sect?><?ENTCHAR sect?><?ENTCHAR sect?> Prato and Woo identified 70 different profitable two-pass treatments, 25 profitable post-emergence-only treatments, and 17 profitable pre-emergence-only treatments.¹⁹ Atrazine was present in the majority of profitable pre-emergence-only treatments, but these were uniformly less profitable for farmers than post-emergence-only and two-pass treatments.

<?ENTCHAR ast?><?ENTCHAR ast?><?ENTCHAR ast?><?ENTCHAR ast?> Corn production data cited here are all for market years; e.g., 2009 means September 2008–August 2009.

<?ENTCHAR dagger?><?ENTCHAR dagger?><?ENTCHAR dagger?><?ENTCHAR dagger?> See http://www.ers.usda.gov/topics/in-the-news/us-drought-2012-farm-and-food-impacts.aspx.

<?ENTCHAR Dagger?><?ENTCHAR Dagger?><?ENTCHAR Dagger?><?ENTCHAR Dagger?> RFS mandate data from Ref.33; bushels of corn converted to gallons at 2·8 gallons of ethanol per bushel. Corn for ethanol data from Ref.32.

<?ENTCHAR sect?><?ENTCHAR sect?><?ENTCHAR sect?><?ENTCHAR sect?> We follow common usage in referring to elasticities with smaller absolute values as “smaller”; e.g., “less than 1” is understood to mean “less than 1 in absolute value” when discussing elasticities.

<?ENTCHAR ast?><?ENTCHAR ast?><?ENTCHAR ast?><?ENTCHAR ast?><?ENTCHAR ast?> The implied price elasticity is the ratio of these percentage changes: −4·4/8·0 = −0·55.

<?ENTCHAR dagger?><?ENTCHAR dagger?><?ENTCHAR dagger?><?ENTCHAR dagger?><?ENTCHAR dagger?> The $1·7 billion revenue gain to corn growers is partially offset by small revenue decreases in other crops, and by decreased payments under the Conservation Reserve Program (CRP), as some CRP land is pulled into corn production by the higher corn price. The gains in corn revenues, however, are much larger than these offsetting reductions. There is still a net increase of $1·4 billion in farm revenues from all ten crops combined (see appendix) plus CRP payments. (The decline in CRP payments, not shown in the appendix, is less than $50 million.) Similar but somewhat smaller results occur in Mitchell’s scenario in which glyphosate use increases.

<?ENTCHAR Dagger?><?ENTCHAR Dagger?><?ENTCHAR Dagger?><?ENTCHAR Dagger?><?ENTCHAR Dagger?> In technical terms, this would imply infinite price elasticity, since a non-zero percent change in quantity would be associated with a zero change in price.

<?ENTCHAR sect?><?ENTCHAR sect?><?ENTCHAR sect?><?ENTCHAR sect?><?ENTCHAR sect?> US Energy Information Administration, “Frequently Asked Questions,” http://www.eia.gov/tools/faqs/faq.cfm?id = 27&t = 4, accessed 2 April 2013.

<?ENTCHAR ast?><?ENTCHAR ast?><?ENTCHAR ast?><?ENTCHAR ast?><?ENTCHAR ast?><?ENTCHAR ast?> Marsh finds that a 1% increase in corn prices is associated with a 0·28% decrease in the quantity of cattle slaughtered, and that a 1% increase in cattle slaughtered is associated with a 0·59% decrease in the price of cattle.³⁹ The effect of a 1% increase in corn prices on cattle prices is thus equal to (−0·28)×(−0·59) = 0·165.

<?ENTCHAR dagger?><?ENTCHAR dagger?><?ENTCHAR dagger?><?ENTCHAR dagger?><?ENTCHAR dagger?><?ENTCHAR dagger?> Leibtag calculates that a 50% jump in corn prices would raise beef prices by 8·7%, implying a beef price increase of (8·7/50) = 0·174% per percentage point increase in corn prices.⁴⁰ His estimates of impacts on other corn-based foods are even smaller.

<?ENTCHAR Dagger?><?ENTCHAR Dagger?><?ENTCHAR Dagger?><?ENTCHAR Dagger?><?ENTCHAR Dagger?><?ENTCHAR Dagger?> February 2013 US city average, all uncooked ground beef, from US Bureau of Labor Statistics, http://www.bls.gov/ro3/apmw.htm, accessed 1 April 2013.