Our members should be aware of a problem involving some farmyard manure (FYM) supplies from certain sources. You are also advised to be careful when eating home-grown vegetables that may be contaminated by a powerful new herbicide that is present in FYM and is destroying some allotment and allotment crops across the UK. Whether some of the FYM that has been delivered to some plot-holders on our allotment site is contaminated I don’t know. The stuff I get from a local farmer is safe, it is suggested that you make enquiries before you use manure from an untrusted source.

It appears that the contamination has come about since grass has been treated with a relatively new hormone based systemic weed-killer containing aminopyralid (used to eradicate docks nettles and thistles in grassland since 2007).  Allotment and veg allotment crops that are grown in soil that has inadvertently had contaminated manure added to it have been wilting and dying . Experts say the grass was probably made into silage, and then fed to cattle during the winter months. Once in the animal’s gut, the grass is broken down and the chemicals in the weed-killer is passed through in the excrement and is especially concentrated in the urine. The herbicide remains present in the silage that is eaten; it then passes through the animal and into the animal's droppings and urine on bedding that is later sold as FYM to many unsuspecting allotment allotmenters! Horses and other animals fed on hay that has been treated with aminopyralid is also a channel.

Dow AgroSciences has sold the herbicide here since 2006 - 2007 and the label stated that manure resulting from animals eating products from treated pastureland should not come in contact with sensitive crops. Apparently the most sensitive vegetables are tomatoes, legumes, salad crops and potatoes. A few ornamental plants are affected, especially roses, phlox and delphiniums. This advice was generally ignored or overlooked by farmers. I personally wouldn’t fancy eating anything grown in this chemical muck (excuse the pun).

Once the scale of this disaster started to dawn, the manufacturer withdrew the product from sale and DEFRA revoked the licence for use pending a review. That of course is not the same as an absolute ban and who knows what similar “nasties” may in future come on to the market with similar problems.

Unfortunately this stuff will be coming through in manure until at least 2012 and probably 2013. That is, assuming the farmers returned any stocks they held and stopped using what was a very cost-effective product when it first appeared on the market.

How do you know it's contaminated?

To test compost, set up at least six 4-inch seed pots, and fill half of them with potting soil. Fill the other half with a mixture of two parts of the compost you want to test and one part potting soil, and be sure to label the pots. Plant the containers with peas (in cool weather) or beans (in warmer conditions). If pyralid herbicide residues are present, germination will be poor, and seedlings that do grow will have curled leaf edges.

To test manure, plant at least six seedling pots with peas or beans, and let them grow for a couple of weeks. Mix a slurry of equal parts manure and water, and strain off 2 cups of liquid. Drench half of the seedling pots with the manure water; water the others as usual. If the manure is tainted, symptoms will appear within a few days.