Kitchen Garden Forum

In the light of my recent ‘accidental’ test of peat and non-peat where I sowed 2 trays of Sweetcorn, one in peat and one non-peat (see Tweet for Peat) I wonder if the KG magazine, via its readers, could possibly conduct further tests, maybe next year. Thus sow 2 trays of the same seeds, one in a peat-based compost and the other in a non-peat compost and monitor progress and give details of both composts. If enough people did this then it would start to give a much better picture of the real situation as to the merits of both types of compost. Oh – and exclude municipal composts.

Also, I would be interested in knowing what the actual costs of production are of the various types of compost and the profit margins. Possibly sensitive commercial information, but KG might have enough clout to get the producers to at least give orders of magnitude. Who knows, we might even begin to move towards standards.

Hi Colin

A good suggestion. I foresee two problems, however:

Those who reuse to use peat will not participate

I assume in my semi-ignorance that all the peat-free composts which contain "green waste" could contain municipal compost materials - for example this well known brand.

Hi Alan,

Point 1 - those who refuse to use peat. Don't think that matters particularly if enough people participate.
Point 2 - yes, that is a problem, so maybe I was wrong to exclude them. If the source is stated then a picture should emerge and it may also give us some idea as to how good these municipal composts are - a sort of third category.

And it would be interesting if the cost of the compost were stated so that we can see where customers are being- how shall I put it - 'overcharged'!

Another problem is we have used the same compost brand for all our potting on etc and have variable results from different batches of the same type of compost.

It's been one of our biggest problems for the last year or two - inconsistency of a product

I can only quote a current problem I'm having as to how confusing the results might be. This year I have sown leeks, kale, celeriac, kohl rabi, cucumbers, courgettes, peppers, chillis, beans & tomatoes from a bag of New Horizons peat free compost left over from last year. I've had good results from everything, despite my normal habit of of using a peat based compost, except for tomatoes which I fear are going to be a disaster.

So I can hardly blame the compost for poor results overall. I do agree that compost quality can vary massively, even under the same brand and type from batch to batch, but is it possible that some vegetables will thrive and some will not in the same brand?

Interestingly, this particular bag of compost which I've used this year has contained lots of live thriving worms. Now where on earth have these come from, I wonder? It's the first time I've ever come across worms in a bag of sealed compost.

According to what the much maligned Alan T said in his statement - some seedlings are particularly susceptible to impurities in compost.

We know tomatoes are a sensitive plant through problems with aminopyralid so maybe there is something in this. However we have two batches of brassicas grown in the same brand compost - different bags and one lot are thriving and the others pathetic, so it isn't that simple. We're going to try feeding the pathetic ones to see what happens.

Beechgrove gardens (BBC Scotland) did a compost trial last year and are doing another again this year

In gardening there are often many variations without apparent reason. The hope is that, with large enough numbers, some patterns will emerge, including inconsistency within batches or brands. Of course storage and age could be other factors.

Looking at the New Horizons non-peat spec I was struck by the fact that no mention was made of the proportions. I'm not in favour of over-regulation, but I do think that a case can be made for some minimal standards here.

I've just taken 3 of my tumbling tomato seedlings out of their non-peat based compost & replanted them in a soil based compost to see whether they pick up & there is any improvement in the way they perform. Kill or cure

glallotments wrote:
Beechgrove gardens (BBC Scotland) did a compost trial last year and are doing another again this year

Here's the Beechgrove fact sheet -

http://www.thebeechgrovegarden.com/fact ... eet_20.pdf

The Which Association has done this very test.

This has profoundly influenced the peat / non-peat debate on this forum, as the headline shows that peat-free can equal and outperform peat based composts.

I had forgotten that I have a subscription to Which so when I remembered I decided to have a look. and their method of testing and results make interesting reading.
Unfortunately, apart from their headline results and best buys these are hidden as member only items. So in the interests of information dissemination here are my potted versions of the results.


Sowing seeds:
- best performers (4* or 5*) all contain peat
- middle range performers(3*) either
- Don't buys(1* or 2*) all peat free


Growing on young plants:
- best performers all contain peat
- middle range either
- Don't buys all peat free


Container plants - best performers either
-middle range either
poor performers either

The container plants test tested potato yields and Busy Lizzie flowering. As one might expect some composts give good results in one area and poor in the other.



Interestingly, the Best Buy Peat Free compost for container plants (a well known "organic and peat free" multipurpose) appears not to have been tested for seeds and growing on as it's name does not appear in the lists so we have no indication of its performance as a multi-purpose.


To illustrate the danger of relying on tests and headlines such as these when all you want is a general purpose multipurpose compose for your small back garden,
One of the items tested in all three categories with a similar name as the above mentioned best buy scored 3* for seed sowing, scored 4* for potato yields and 3* for Busy Lizzie flowers but was a Don't Buy for growing on (although best peat free on test)


I will now state that I am not in any way connected to the compost industry or Which?.
I would further suggest that If you are more interested suggest you take out the cheap trial offer for Which? and check for yourself. (don't forget to cancel before the end of the period).
This will also enable you to check that if my conclusions are erroneous or not.

It is also worth noting that the composition, safety and user friendlessness of the composts was not tested.


MikA

The Beechgrove tests showed that peat compost outperformed any non peat based product. Their factsheet explains finding http://www.thebeechgrovegarden.com/factsheet/factsheet.php?fact_id=364 scroll down to handy hints

Glallotments

A small chastisement on the use of words:

The Which tests clearly shows that a peat free compost CAN perform as well as peat based for particular purposes within the parameters of their test. To use the word TOO at the end of your sentence about the Beechgrove tests is incorrect.

When I have time I will look at the Beechgrove link to make my own conclusions.

MikA

OK I've removed the too so I don't mislead anyone. The too wasn't really intended to necessarily refer to the Which reports though more generally other peoples comment about their observations.

The problem with the Which tests is that they are actually a very small sample. And we all know how variable plants can be, for no apparent reason, not to mention the problem of controlling the growing conditions - moisture, light, temperature, etc.

I must also confess to a degree of scepticism regarding Which tests. Back in the early 80's I had series of articles on growing tomatoes published in Garden News. Thereafter for a while at least, Gardening Which sent me articles to comment on.

Then there is the problem of consistency from batch to batch, year on year. Whether larger scale 'public' trials will achieve anything is also debatable. So I come back to my original comment that without some minimum standard, there can be no definitive answers.

I note that JW has posted another Google-enhancing link on the other topic. Can't really see how admonishing Alan Titchmarsh adds anything factual to the debate.

Colin

I share your scepticism about the Which trials but your topic asked for people to conduct a peat v peat free test which the trials do in a reasonable albeit limited way.

I agree on the need for a standard and a model already exists:

The British standard for topsoil (BS3882:2007) requires tests for PTEs (Potentially Toxic Elements) which could be what make some peat free stuff so useless. I am sure it would not be beyond the skill of producers to carry out testing as required for topsoil on all their composts and if they did I would heartily endorse their products.