Picture of Karl Tupper

Karl Tupper

Strawberries & ammonia? The folly of chemical farming

My colleague Susan Kegley alerted me to a new study in Environmental Science and Technology (ES&T) that illustrates the absurdity of chemically-dependent agriculture — particularly the lengths we'll apparently go to keep the needle in. Scientists are actually studying injecting up to 32,000 lbs/acre of concentrated ammonia into the soil to counteract a fumigant pesticide's ozone-depleting effects.

At issue is methyl bromide — a neurotoxic pesticide used in strawberry production in California. Methyl bromide destroys the ozone layer, so it's being phased out under the Montreal Protocol, the international agreement that bans ozone depletors. Growers were supposed to stop using it by 2005, but they've been successful in winning "critical use exemptions" to the ban, arguing that it's impossible to grow strawberries without fumigants.

Going organic is apparently unthinkable, and so conventional growers have been clamoring for "alternatives" to methyl bromide. If you read GroundTruth regularly, you already know that California regulators recently approved methyl iodide as one such "alternative". (PAN Executive Director Kathryn Gilje has the details in her blog.) Rather than moving strawberry production towards more sustainable practices, this approval replaces one volatile, neurotoxic, ozone-deleting chemical with another volatile, neurotoxic carcinogen.

The article in ES&T represents another, almost equally absurd "solution". "Depeleting Methyl Bromide Residues in Soil by Reaction with Bases" proposes to use another layer of chemical applications to counteract methyl bromide's ozone depleting side effects. The idea is that methyl bromide would be applied as usual, and then after it's done its job, concentrated ammonia would be pumped into the field to destroy it before it could escape into the atmosphere and damage the ozone layer. There are a few problems:

  • The amount of ammonia needed is huge: If the proportion used in the ES&T paper was scaled up, a typical methyl bromide application of 200 lbs/acre would require from 13,500 to 32,000 lbs of concentrated ammonia per acre. That's a lot of ammonia, and we're talking about concentrated ammonia, which is a lot more noxious (and dangerous) than the diluted stuff you can buy for household cleaning.
  • The technique relies on special tarps, so called "virtually impermeable films" (VIFs), to seal the methyl bromide in the field and keep it from escaping into the atmosphere. VIFs are indeed impermeable to methyl bromide in the lab, but that doesn't translate in the field. The problem is that strawberries are grown in raised beds that are tarped individually and "sealed" by shoveling dirt over the tarp's edge. So no matter how good your tarp is, you still loose some gas out of the edges, and because rows are tarped individually, a strawberry field has a lot of edges.
  • It's expensive. Fumigation with methyl bromide is already costly, and adding tens of thousands of pounds of concentrated ammonia per acre isn't going to help.

"The significant problems we face cannot be solved at the same level of thinking we were at when we created them." Einstein was right, but we don't have to be Einsteins to see that the failings of chemically-dependent agriculture can't be solved with more chemicals (i.e. ammonia) or different chemicals (i.e. methyl iodide).

Picture of Karl Tupper

Karl Tupper

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