Contaminated manure.

I had expanded my backyard garden last fall.  The new beds have been filled with a combination of shredded leaves and homemeade compost. Unfortunately there was not enough material to finish the job.  This spring I sourced and purchased a truckload of composted manure from an area farm that sold its compost locally.

I figured squash and potatoes would do okay in the roughly processed compost as it continued to age.  The potatoes were very slow to start.  Many didn’t emerge at all.  The squash seemed to do okay.  Some of the potatoes rotted in the ground so I thought it might be a bad batch plus the fact that we were having a cold spring and I did water the manure so, not ideal starting conditions.  I ordered some more seedling potatoes and planted again.  When the potatoes finally did emerge, there were still several gaps in the beds, and some potatoes were severely stunted.  The ones planted where there was no manure came up just fine.


Herbicide damage on potatoes.
Gaps in bed.

Fearing blight or a virus, I took pictures and researched online.  Long story slightly longer, I am fairly certain that the manure contains a persistent herbicide.  I don’t have the resources to find out which one but it follows the same patterns that other gardeners have experienced with aminopyralids and similar types.

Herbicide damage on potatoes.
Stunted growth.

I’m discouraged but thankful I’m learning about this now.  I think of the small market gardeners who had their entire growing area wiped out b/c of tainted manure.  The insidious herbicides do not break down in a ruminant’s digestive tract so if your animals got into treated ditch vegetation without you knowing, their manure could ruin your garden.  Farms or stables that purchase hay, manure, or compost may not know they have purchased product that contains these chemicals.  The seller may not know it themselves.  Furthering the frustration, legal challenges have ruled in favour of Dow Chemical, i.e., the company does not have any legal responsibility as to the use of its chemicals, that responsibility lies with good stewardship.  Canada has not banned these types of chemicals 

A couple of articles from many are available here:

from the Royal Horticultural Society

from Oregon State University

There are some crops that can be grown in this kind of compost, for example, squashes and grasses.  However, many vegetables are sensitive and will be stunted.  (nightshades, legumes, umbels) It will be several years before the microbial action will completely break down the herbicide.  It seems the best course of action is removal and persistent processing for at least a year.  For me, this was a stark reminder of three things:

  1.  how much I don’t know about the chemicals that go on or into our food systems,
  2. how small amounts of chemicals can affect systems many miles away, and
  3. how little recourse there is beyond individual responsibility.

It was a sobering lesson.


3 thoughts on “Contaminated manure.

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