Kitchen Garden Forum

We have planted up 6 giant sized Tomorite grow bags with tomatoes in our plot greenhouse using the same brand of grow bag. The bags are side by side and have been given exactly the same treatment. We have used ring culture and filled the rings with compost from additional grow bags. Varieties are the same as in other grow bags.

The plants in five of the grow bags are growing well and are very healthy but in one bag the plants are pale and sickly and hardly growing at all so I can only assume that the grow bag compost with in the bag or used to fill the rings is to blame. They were planted up at the same time too and looked equally healthy at this stage.

More grow bags have been used in our garden greenhouse and again things seem to be growing well. I emailed the company but the response was more or less that it may be something other than the grow bag but the only different variable is the grow bag compost. I can't imagine a disease being so selective as to pick on the tomatoes growing in one bag and ignore those growing immediately alongside them. Incidentally the sickly ones are not the ones next to the door so any air-borne disease would have to pass other tomato plants to get to them. Has anyone else had a similar problem?

We have also have some poor germination from some of the seeds sown this year or once germinate the seedlings have failed to thrive. These have been planted in peat free multi-purpose compost. This time the company wrote that I should have used compost meant just for sowing seed. In the past we have always used multi-purpose compost successfully - I always thought that was why it was called multi-purpose!

One of my suspicions relating to non-peat composts is how much does one binful of lawn-weedkiller-treated lawn-clippings (for example) get diluted by appropriate material during the composting process. Could all the crap end up in a small number of finished product bags, both active and concentrated enough to cause problems?

This sounds like that, or poor mixing of good ingredients

I share that concern too Peter and raised it in an email reply to the company.

My question was:
" Another cause for concern is the use of green waste in composts which I notice you don’t mention. Is this because you don’t use it? If you do how do you ensure that persistent chemicals are not present in the green waste".

Their reply was:
"As part of the government initiative to reduce the amount of peat used in our composts, we are using other materials such as green compost in our mixes. Green compost is an approved input for organic farming, as described by the Soil Association. Whilst they understand that the green compost should ideally be produced on the organic holding they support the principle of green compost production by local authorities and allow the use of PAS100 compliant material. We can assure you that we buy only from PAS100 accredited producers and all of our compost mixes undergo vigorous testing at our research station for many years prior to release onto the market. Results of this research show that reduced peat and peat-free composts give the same, if not better results than composts containing peat".

It all sound good to someone who hasn't had the misfortune of finding out that organic doesn't always mean what we think it does? I'm not sure what a supplier has to do to be PAS100 accredited - I'll try t find out but I can't see how this can protect against rogue materials getting into the green waste. Any treatment given is unlikely to remove persistent chemicals such as aminopyralid or clopyralid. Goodness knows what ends up in LA green waste.

I've found this
http://www.environment-agency.gov.uk/static/documents/Business/Technical_report_for_compost.pdf

Nothing really reassuring there and this statement
"Horticultural Grade material: Compost following this route is not regulated. Generally speaking it is not in the public interest for the Environment Agency to take enforcement action unless there is a serious problem".
Seems to mean that anyone can sell anything for garden use.

This link mentions what is tested to conform to PAS100
http://www.eurofins.co.uk/our-services/agro-sciences/compost-testing-to-pas-100.aspx

By the way please don't tell me I can avoid this problem by using my own compost - we haven't enough to meet our needs!!

When I go down to the rubbish dump and see what is recycled in the wood waste......

Hmmm.

Being sufficiently educated to realise that one cannot test 25kg of compost for "anything that could cause a problem" and that it is much easier to test for a specific chemical that is suspected to be present, I can see what's happening here.
This is generic contaminated land type tests, those which would cover general land, as opposed to the specific tests that might be done on, let's say, an old gas works where creosote and other hydrocarbons might be present.

Believe me, I have great sympathy for these composters and bagged product producers. How they could economically test for every eventuality in every batch, when the contaminant(s) could be one step along the pile from the sample, heaven only knows.

Perhaps a better solution would be the blanket banning of environment-persistent biocides such as Sodium Chlorate, Aminopyralid, et al.

But how long would that take and how long before "that half-bottle I bought in 2011" is finally finished? My late parents shed had an original formulation can of SBK Brushkiller when I cleared it and if memory serves me right that was withdrawn/re-formulated last century so it would not contain traces of dioxin.

Sadly we will face the possibility of random contaminants for the forseeable future, with the only practical solution being lots of repeated batch or heap division and blending to spread any contaminants as thinly throuth the finished product as possible.

Regardless of the above a tighter definition of acceptable composting ingredients is obviously needed. Timber sawmill waste is fine but any artificially reconstructed wood products need to go for burning. e.g. plywood, particleboard, chipboard, mdf, any treated timber. That should be carbon neutral as both composting and burning release the carbon, but timber production is in Europe something like cut 3 plant 4.

Dear Gallotments,
have you checked to see whether all the holes on the underside of the growbag have been pierced? This is a more likely cause of poor performance in one growbag than contamination. Green waste is turned and stirred many times during the compost making process and thus any contamination would be spread amongst all the bags in a batch.
Regards Sally Wright.

Dear All,
I forgot to mention that germination tests are performed to see whether there is any chemical contamination. They will also do heavy metal tests. Being sued for selling something toxic is not good for turnover.
Regards Sally Wright.

I did some research into commercial composts after raising my post on "The contents of commercial composts". viewtopic.php?f=8&t=9614

When I found out how green composts are made from the rubbish put into council skips and the testing? for PAS100, I decided this was too depressing, so stopped and went back into the garden to get over it.

The bags do have holes Sally. The bags that we bought were not necessarily from the same batch. We could easily have had one bag that was from a completely different batch even if they were bought at the same time which they weren't as we can't transport all the bags that we use at once.

I realise germination tests are carried out as it says in the link but they can't test everything to the extent that any contaminant will be revealed or even test all types of seeds. Some will be more sensitive to contaminants than others. I'd also be interested to know how the tests are carried out.

I think it is very unlikely that a compost maker will be sued (from what has happened in the past they will realise just how difficult it is to prove any negligence) and it seems there is no likelihood of enforcement action as stated in the quote above.

From our experiences with aminopyralid contamination it difficult to prove or for anyone to trace where the contamination originates even if the will is there which doesn't appear to be the case.

sally wright wrote:...Green waste is turned and stirred many times during the compost making process and thus any contamination would be spread amongst all the bags in a batch.....

Good to hear, the only method I have seen involved 6' to 8' high & wide rows under wall-less barns come bikesheds. Not sure how the rows were initially created, but they were turned inside out regularly by a heath-robinson machine like a cross between the business ends of upright vacuum cleaners, combine harvesters and a giant corkscrew attached to a wheeled and powered football goal that ran down row one, up row two etc.
Not mixed much beyond the initial blend of grabfuls from different heaps other than by being loaded & unloaded for transport, available by the bag or bring your own lorry (minimum load size) both straight by front loader to truck or bagging machine from the finished product pile.

Thinking about it these moves will mix quite a bit, but is it random enough or will the same cubic metre make it through from one end to the other of the process or not?

Plus what if a many lorryload pile of farm manure were one ingredient and their feed had included the dreaded aminopyralid?