Picloram damage on lettuce. Photo by Sue Colucci
I know the issue of persistent herbicides contaminating
manures and composts is important to many of you because you contact me by phone and email, send me pictures, and have lengthy on-line forum discussions about it, so I thought many of you would
be interested in this:
The US Composting Council has a position paper posted on
their website where they outline the damage that has been caused by persistent
herbicides in manure and compost. They are asking the EPA to address this issue
by halting sales of persistent herbicides in the U.S.. You can read that
position paper at http://compostingcouncil.org/?news=persistent-hebicide-issue-paper-now-available/ (it is
big and takes a few minutes to download).
This is a reminder to all of you who use manure, compost,
straw, straw bales, hay, and grass clippings in your gardens and on your farms.
Know where your material comes from before putting it on your soil. Ask
questions. If in doubt, do bioassays. How to do a bioassay is described in the
NCSU Herbicide Carryover leaflet found here http://www.ces.ncsu.edu/fletcher/programs/ncorganic/special-pubs/herbicide_carryover.pdf
. Katie Jennings, weed scientist, and I
are in the process of updating that leaflet.
Updates will include removing fluroxpyr and triclopyr from the
herbicides of concern AND expanding the length of time that the bioassays
should be done (at least five weeks). You can read my blog posts on the
bioassay experiments with tomatoes that made me change that here: http://ncalternativecropsandorganics.blogspot.com/search/label/herbicide%20carryover
Manure and composts made from manure are wonderful soil
amendments, but some people are steering away from using them because of the
herbicide concerns and the difficulty in finding out of the materials they want to use are clean or not.
Aminopyralid damage on tomatoes. Photo by Jeanine Davis
Pepper plant growing in soil amended with aminopyralid contaminated compost (top) and pepper plant from same group of transplants but planted in soil that was not amended with compost (bottom). Photos provided by home gardener.
Labels: compost, herbicide, herbicide carryover, manure