Damged - and recovered - tomato plants.

Compost-herbicide damaged  young tomatoes but they out-grew the effect.  Should the compost  have been allowed for certified organic production?

In a recent ruling (June 20, 2016) the US District Court of Northern California nullified USDA’s National Organic Program NOP “Guidance Document” pertaining to contaminants in compost. The result of the ruling is likely to bring back into focus a long-simmering issue of herbicide residues inadvertently present in composts. The plaintiffs, the Center for Environmental Health, argued that formal rule-making would be required for USDA to issue such a “guidance” since it in effect “amended existing national organic food regulations”. The court agreed.

The NOP 5016 “Guidance Allowance of Green Waste in Organic Production Systems” (2010) permitted organic producers to use compost containing any accidental synthetic pesticides. The action was a result of the case against composter Nortech Waste LLC, brought by the California Department of Food and Agriculture (CDFA), which found that the compost product contained trace levels of an insecticide bifenthrin, interpreted in CA as making the compost non-permissible for organic farming.  However, USDA found no residues of bifenthrin in soil or crops when the contaminated compost was actually used in agriculture.

Unfortunately, the NOP 5016 guidance over-stepped a decade of experience with herbicide residues in composts which, if present above certain thresholds, can cause visible plant injury. Now, with the USDA guidance in disarray, focus is likely to return to residues levels in composts,- and what if any action to take. Recent research by Woods End Labs in collaboration with scientists at NCSU and Scott’s Miracle-Gro published in the Journal of Environmental Horticulture shows the high replacement value of dairy-manure compost in conventional growing media. “All bets are off on this excellent compost development if we have bio-active contaminants in planting media, regardless of what USDA may think”, says Brinton.


Woods End Lab’s herbicide bioassay establishes threshold levels for traces of herbicides present in composts. The result enables growers and composters to avoid ill effects.

Woods End Labs may have been the first to discover trace herbicide residues in compost in 1998 and wrote a proposal to OFRF (CA) to determine by bioassays if such levels were actionable. The proposal was rejected. Shortly afterwards, alarm was raised in the state of Washington, due to range-land picloram residues from the WSU campus operations showing up in a community compost-treated garden.
For Woods End lab, the answer has always been to perform careful bioassays, which its researchers developed and published. Such assays can determine what if any actionable thresholds exist, and using the information, help growers and composters navigate to a safe position. NOP staffers were present in WA when these events occurred so it is  surprising they attempted what appears to be a run-around ruling that sweeps a decade of careful scientific work under the rug.  Composters and growers can obtain a Wood End certificate of analysis for herbicides residues and guidance on best-use to avoid effects, by writing to the lab @ woodsend.com.