Its well known that well rotted manure is one of the best ways to improve soil structure and texture, adding bulk, nutrients and good drainage to the site and your growing plants but reports over the last few years have revealed growing concerns over the use of manure.
Specifically this has been due to the herbicide Aminopyralid, a hormone herbicide, manufactured by Dow Agroscience enabling farmers to apply it to large areas of land in order to protect crop, killing weeds such as Docks , Thistles and Nettles. In 2008 the use of this herbicide was suspended but the damage had already been done. Small businesses and even those with allotments have been affected as the food chain continued and manure sold on and distributed. Thus those that made their living selling plants and vegetables and those simply enjoying the delights of the allotment found crop destroyed and had to pay a high price to remove and replace organic matter and crop.
Quoting the Health and Safety Executive :
"Aminopyralid is an effective herbicide with a low toxicity to mammals. However residues of it can remain in grass from treated land and pass into the manure of grazing livestock, where it remains tightly bound to the plant material until it decomposes. Similarly, the substance can also remain in grass fed as hay or silage to horses and housed cattle, again passing through the animals into the manure.
If manure is applied to soil or crops before the plant material in the manure has fully decomposed, susceptible crops may be damaged.
Labels of products which contain aminopyralid therefore include warnings not to use manure from livestock…until all plant material had fully decomposed.
However it would appear that in the past the label precautions in respect of manure may not always have been followed when manure has been supplied to allotment holders and gardeners."
Recent reports from allotments in Edinburgh (June 2010) also traced contaminated manure that was being sold onto members of the public and further reports (July 2011) also reveal that Aminpyralid symtpoms have been found in vegetable crops within Britain. Nevertheless Dow Agroscience have reinstated the herbicide and Clopyralid, used for the same purposes mainly in France and the USA, is another herbicide still registered for use on grass, hays and grain crops. Roughly 60% of us use grass clippings in out compost, but is this safe? A source from the University of Washington stated ‘The risk of contamination of some animal manures with clopyralid remains’.
Despite restrictions, symptoms of aminopyralid damage were recorded on crops growing in allotments in Edinburgh, UK as recently as June 2010; enquiries traced the source of contamination to a farm supplying hay to the stables from where bags of manure had been obtained. Symptoms of aminopyralid injury to vegetable crops were reported by small farmers and gardeners in Britain in July 2011.
Signs of possible damage
The main signs are curling, twisting and deformed leaves as well as leaves appearing darker and fern like. Plants predominantly affected are Tomato plants, beans, Sunflowers and potatoes.
What can we do?
Firstly, sometimes us gardeners just have to hope for the best like with any yearly crop something always gets eaten or disease that wipes a whole crop out. We should not only be regularly checking are crops for possible signs of any pest or disease, whether it be related to a contaminated herbicide in out organic matter or not, but perhaps we should also consider where we buy or purchase manure from and what chemicals we use too. Checking labels to products and asking questions from you local supplier should be asked if you are worried or perhaps trying out use of a different organic matter could be the solution.
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