Killer soil

Herbicides are making their way into commercial compost, unbeknownst to consumers or often even the makers of the compost.

Mother Earth News reports this month that the herbicides clopyralid and aminopyralid—both produced by DowAgrosciences—can persist in hay, manure and compost for years. When used in an organic vegetable garden, growers are finding low yields and weak crops. Grab ’n’ Grow, a commercial compost maker in Santa Rosa, Calif., found residues of clopyralid in a batch of its compost in 2002. Grab ’n’ Grow manager Don Liepold told the magazine he’s been testing for and finding herbicide residues in a host of organic materials.

It’s hard to trace the source of these herbicides, with materials crossing state lines and no one knowing they’re laced with them. Testing is expensive—$350 or more per sample. Liepold says he spent $20,000 in lab fees in 2008 alone. The Environmental Protection Agency tested both herbicides before it was known how persistent they are in compost and before lab tests were able to detect residues at destructive levels, reports the article, which calls for the approval of the pesticides to be revoked by the EPA before more damage is done.