Contaminated compost

The other day I was singing the praises of some composted stable manure that I bought earlier in the year, but I have changed my tune now. I am fairly sure that it is contaminated with aminopyralid weedkiller. This type of weedkiller is used by farmers to control weeds on pastureland. Animals grazing this land ingest the weedkiller (which does them no harm), but it is passed through into their manure – some of which evidently makes its way into commercial compost!

I won’t attempt to explain the whole saga in detail, because that has been done before – most notably by Sue Garrett on her blog Our Plot At Green Lane Allotments - but I just want to provide some evidence that although this issue is supposedly a thing of the past, it isn’t. In theory, according to regulations introduced in 2010 manure which potentially includes this type of weedkiller should be retained on the farm of origin, but it appears that this does not happen in every case. I bought 12 bags of  composted stable manure in March of this year, and used most of it in the big pots I am using for growing tomatoes and potatoes. I also dug some into my raised beds as a soil-improver.

The main symptom of contamination is distortion and malformation of plants stems and leaves, particularly at their growing points:

The leaves are thin and spindly, often described as “fern-like”, and are curled inwards.

In potatoes the leaves adopt a distinctive “cupped” configuration.

It’s not all bad though, because the first truss on each plant seems to be forming OK. Many of my plants this year are Beefsteak varieities, well known for thier irregular shape, so I was fully expecting some ugly specimens! This, for instance is “Noire Charbonneuse”.

This is “Dinnye”:

And this is “Banana Legs”, which has elongated yellow fruits: