Berkeley, Calif.-Researchers believe they have found that ammonia fertilizer may degrade methyl bromide, which is on the verge of being banned internationally as a soil fumigant because of what it’s doing to the ozone layer and the health of farm workers. The U.S. Environmental Protection Agency planned to phase out the neurotoxic pesticide by 2005, but farmers pressured the agency to grant special exemptions to use methyl bromide on certain crops, such as strawberries. A recent article in Environmental Science & Technology reported that earlier studies had already found that the fumigant degrades quickly to harmless methanol and bromide under alkaline conditions, which are present in fields due to agricultural lime and ammonia fertilizer. Laboratory tests by USDA Soil Scientist Scott Yates and others found ammonia works about 16 times faster than other substances, and under simulated field conditions degraded more than 99.5 percent of the methyl bromide after just eight hours. The study shows that farmers could cut methyl bromide emissions so effectively that the end result would appear as if the pesticide had been banned, suggested Robert Rhew, biogeochemist at the University of California, Berkeley. But he wondered if the process will work in the field. Rhew and Susan Kegley, principal scientist at the Pesticide Research Institute, a company that consults on pesticide use, pointed out that the plastic tarps used on fields do not provide the tight seals available in a lab because the tarps are frequently blown off by the wind or pierced by roving deer and birds. Kegley also wondered about pursuing this path since this research does not take agriculture in a more sustainable direction. “The risks for applicators remain high,” she cautioned. “Research efforts are better directed to non-chemical methods of soil pest control, rather than attempting to perpetuate a system that utilizes highly toxic fumigants.”
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