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Contaminated compost Hampers Spring Planting
By Kevin McEnnis
(Kevin McEnnis owns Quetzal Farm near Santa Rosa and is CAFF’s North Coast Regional Coordinator)
 The author in his greenhouse, examining young pepper plants that will make up part of his planting mix n Quetzal Farm this year.
(photo: Will Stockwin)
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Spring planting is in full swing in California. Farmers, like myself, are stocking up on truckloads of compost to build soil organic matter, retain moisture, and add nutrients. This year is different, however, the compost that we assumed was contaminant free after an intense process of microbial decomposition has turned up with a few ugly surprises. I learned this one April morning when I went to my local compost supplier to order a load of quality compost for this year’s crops.
The mood was not a cheerful one when I stepped into the office of Grab and Grow Soil Products. On the first day of spring the results of a test for clopyralid had indicated a positive result. The compost that I use and depend on to build soil organic matter contained a detectable and possibly harmful level of herbicide. As an organic farmer and activist for sustainability and recycling, I had to question whether or not I could buy the product. The brief fact sheet my compost dealer gave me raised even more concern. Some of the most clopryalid-susceptible crops, peppers and tomatoes, are two of my most profitable crops. And their field was due for a heavy application of compost in a few weeks. I did not buy compost that afternoon. I needed to learn more about what several parts per billion of a chemical would do to my farm and my organic status.
The discovery of herbicide residues in finished compost is a very recent problem. In May of 2001, an organic farmer in Washington State had his compost tested after most of his tomato plants failed to grow, and those that grew were stunted and deformed. A weed killer called clopyralid was detected. Simultaneously, Washington State University began publishing reports of contamination with the herbicide in their compost. Clopyralid, the active ingredient in many herbicides used to kill broadleaf plants such as star thistle and clover, does not break down significantly in the composting process. Clopyralid was first identified in the green waste received for composting, especially grass clipping from lawns were treated to selectively kill broadleaf weeds. Clopyralid is also used extensively on rangeland to kill star thistle. When livestock eat pasture treated with clopyralid, the chemical passes through their digestive system unharmed.
Effects on Farm Crops
Farms and gardens in Washington State have seen some damage to crops from the use of clopyralid contaminated compost. There has not been extensive testing of what concentrations will cause damage to plants, but there are reports of stunting and deformities at around 10 ppb. To find some answers, I spoke with Will Bakx, one of the owners of Sonoma Compost. Bakx is the chairman of the California Compost Quality Council, on the board of California Organic Recycling Council, and the Executive Committee of the California Compost Coalition. Bakx and others have been looking hard at clopyralid’s effect on the compost industry in California. He and most compost suppliers in the state are greatly concerned about clopyralid. Their very industry is at stake. Compost contamination with clopryalid would have ripple effects on the farmer’s who use compost and California’s efforts to reduce the amount of material going into landfills.
His information allayed some of my immediate fears. In our county and many others, Agricultural Commissioners and municipalities have called for an immediate, although voluntary, discontinuation of clopyralid. They are also trying to educate clopyralid users to not send treated feedstock to be composted. Bakx thinks that this program will start to show an impact in a few months. Speaking about his customers, he was optimistic that they would participate in a voluntary program to reduce the use of clopyralid. “Most people that leave green waste buy it back again as finished compost,” he said. There have been no reports of crop damage in California where clopyralid has been used since 1997. According to Bakx, the incorporation of one to two inches of compost containing 5-10ppb of clopyralid should not pose much risk to even the most sensitive plants such as clover, peppers, tomatoes, beans, or lettuce. He pointed out that compost has probably been contaminated for the last three years and they have received no reports of crop damage.
Organic Certification Worries
John McKeon at Grower Certification with the California Certified Organic Farmers was able to give me some sense of what effect clopyralid will have on farmer’s organic status. “Technically it won’t endanger certification – depending on the nature and the quantity of the application.” When I pushed the issue further and asked what happens if a farmer applies compost known to be contaminated, he indicated that the farmer would probably not be decertified, but that they would not recommend applying the product because of the potential impact on crop yields. In the short term, it does not look like applying compost this spring will damage your organic status in most situations. There simply are no answers about the effects of clopyralid in the long term.
Legislation on the Way
The California Department of Pesticide Regulation has initiated cancellation proceedings on clopyralid products registered for residential lawns. Assemblyman Fred Keeley has a bill in the California State Legislature that would convene a committee to look at persistent herbicides and direct the California Environmental Protection Agency to study and possibly take away the registration for persistent herbicides such as clopyralid. The California Certified Organic Farmers and the California Compost Coalition have endorsed the bill. Dow AgroSciences and the Cattlemen’s Association are opposing the bill. (For more information on this bill, see “State Cancels Clopryalid Herbicide Use on Residential Lawns.”)
In my efforts to find answers to my compost questions, I was left only with more questions. I decided to use the compost that I purchased last fall, even though this year’s vintage has tested positive for clopyralid at 5 ppb. I have decided not to buy new compost this spring and rely on organic fertilizers. I will wait and see if residue-free compost will be available in the future. I fear that my decision to wait, along with many other farmers doing the same, will affect the compost businesses in my area. If we don’t buy their product this year, will they be here next year when we look to buy another load of “black gold.”
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