Allotment holders and vegetable growers across the country have been reporting crops failing and being killed following the addition of manure to the land. Some crops, like potatoes are very badly effected whereas others are less affected.
It appears that the problem is linked to a new herbicide (a hormone weedkiller) aminopyralid being used by the farmers.
The most sensitive crops affected are:
The list is not exclusive – these are just the plants most affected .
My understanding is that the product is licensed for use on grass land but is not licensed for use on wheat etc although anecdotal evidence suggests it is being used on cereal crops despite licensing restrictions.
You will appreciate that I am being careful what I say about a product that a large chemical company has spent more than $80 million bringing to market with a large and powerful legal department.
The active chemical, aminopyralid, is present in:
The residues are getting into the manure by two routes. Where grass land has been treated with aminopyralid containing herbicides and cattle or horses grazed on it, the chemical is excreted into manure. Dow actually state that ” Aminopyralid is water soluble and is excreted in urine relatively rapidly”
The other route is direct from straw used as bedding where the crop has been treated.
The net result is that we now have to treat manure as a potential problem. Stables and many cattle farmers buy in their bedding straw and, although they may be able to state they have not used the product on their grass, they may not know that aminopyralid has been used on the bedding.
What to do if Your Crops are Affected
If you think your plants are being affected then the first call should be to the person who supplied the manure. If possible they should try to confirm whether an aminopyralid product was used on any grass, hay or silage fed to the animals which produced the manure or on the bedding. They may need to trace the original source if the grass, hay, silage or bedding straw was obtained from elsewhere.
If you are reasonably certain that aminopyralid was used, then Dow AgroSciences should be contacted for further advice at firstname.lastname@example.org.
There is an FAQ on their website here
How long is the Manure / Manured Soil Contaminated
This is an incredibly potent chemical, effective in small amounts. How long it remains potent in manure is dependent on how much was there initially and other factors. Probably, and only probably, it is safe to plant in the third year after application.
If buying in manure that may be contaminated, then I would test it by mixing 50:50 with a known multi-purpose compost and trying a tomato plant or bean and seeing what happens.
If you think it is contaminated, compost for a year or three and re-try.
Are the Crops Safe to Eat?
Dow spent an awful lot of money getting approval in the USA and EU. They state that: “Aminopyralid does not bioaccumulate or build up in animal or plant tissue. ” They also state “Animals high on the food chain… are not expected to acquire concentrated doses of this chemical by feeding on contaminated plants or animals”
Even non-organic gardeners like me seek to minimise our uptake of pesticide and herbicide residues in our food and we have seen products – even medicines – heralded as safe withdrawn when unexpected side effects appear as the product goes into general usage.
When time-tested safe herbicides like Amcide (ammonium sulphamate) are de-licensed it is galling that a product that can have such devastating long term persistence and transmission via the food chain is approved. The irony is that this will particularly hit organic gardeners who use manure to avoid the use of direct chemical inputs.
Please note if commenting that I will edit / remove posts that could make me liable for legal action.
Finally thanks to David Hampsey of the NVS for his input and provision of some research materials for this article.
I’ve taken a few photos of the effects on a plot on our site to help with identifying the problem – Contaminated Manure Update