Connie from Portland, Oregon writes
Manure in the PNW keeps coming up with this herbicide in it because of using on hay for feed. The professional compost facility said they had a hard time finding a source that tested negative for it and they were being tested weekly to regain their certification
Per the manufacturer for Black Kow Composted Cow Manure 0.5 - 0.5 - 0.5, clopyralids are of major concern on the West Coast, especially. Residues from these herbicides will dissipate if the manure is aerobically composted over a period of time. Black Kow composts their products for 10 to 12 weeks, then cures for an additional 6 to 8 months. They routinely perform growth tests and lab tests to check for contaminants, and they have never found herbicide residues in their products. They do not test every single bag, so they cannot guarantee 100% that there are zero residues ever. However, the manure is sourced from dairy farms which also have strict herbicide requirements to prevent consumption of residues. You can always perform a growth test in the following manner for exra security, if desired: Mix Black Kow 50:50 with clean sand. Plant 3 to 4 seeds, water, Plant 3 to 4 seeds in a sterile, peat-based potting soil. If seeds germinate in both mixes, then the compost is fine.
Answer last updated on: 11/03/2022
