The perils of bought potting compost

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Weedo
Barbara Good
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Re: The perils of bought potting compost

Post: #289406 Weedo
Wed Apr 19, 2017 11:02 pm

The pics Odsox posted don't look like herbicide damage to me - certainly not hormone type products (phenoxy's) or Glyphosate. While not discounting some of the other herbicide types, I would be very surprised if you could get seeds to germinate in the contamination levels were this high.. The interveinal chlorosis and necrosis seem more typical of severe nutrient deficiency, most likely Iron and Manganese (but could be more complex) Mushroom compost is almost all organic and "spent" material is normally very nutrient poor, at least for green things. I suspect that as the plant grew and you fed them, the problem lessened?

Personally, I would never buy compost from recycled garden waste or use spent mushroom compost as anything but an organic bulker with other materials.

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Odsox
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Re: The perils of bought potting compost

Post: #289410 Odsox
Thu Apr 20, 2017 7:53 am

Weedo wrote: I suspect that as the plant grew and you fed them, the problem lessened?

No, feeding did nothing and most of the plants died.
I don't agree that it was "severe nutrient deficiency" as all the plants were only a week or two old and were grown in seed compost with fertiliser added (by the manufacturer)
I've been growing my veg plants exactly the same way for umpteen years and last year was no different. So from when Adam was a lad up to 2014 I had no problems, 2015 slight problems, 2016 sever problems, 2nd sowing in 2015 with different compost and 2017, no problems whatsoever.
I would think that points to something untoward with the media rather than cultural ?
Tony

Disclaimer: I almost certainly haven't a clue what I'm talking about.

Weedo
Barbara Good
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Re: The perils of bought potting compost

Post: #289417 Weedo
Thu Apr 20, 2017 10:48 pm

OK
Part of my job has been investigating claims of off target herbicide damage on crops - I have never seen this type of damage as a result of herbicide overspray or contamination but will investigate other possible products further. Unfortunately there is no chance of a soil analysis.

Any ideas of what the culprit may be - potentially different products and usages in your patch compared to mine.

Weedo
Barbara Good
Barbara Good
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Joined: Thu Jun 30, 2016 4:47 am
latitude: 35.0886S
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Re: The perils of bought potting compost

Post: #289418 Weedo
Thu Apr 20, 2017 11:54 pm

A couple of questions if I may re potential herbicide damage
are the plants being grown indoors and with heat?
has any additional nitrogenous fertiliser been used?
are Triazones (not Triazines) still in common use in your patch?

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Odsox
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Re: The perils of bought potting compost

Post: #289423 Odsox
Fri Apr 21, 2017 2:48 pm

Weedo wrote:A couple of questions if I may re potential herbicide damage
are the plants being grown indoors and with heat?
has any additional nitrogenous fertiliser been used?
are Triazones (not Triazines) still in common use in your patch?


OK, I grow just about everything under cover, except maincrop potatoes and peas. The most affected plants were my tomatoes which were grown in 3 different locations; greenhouse, polytunnel and conservatory. No heat was used since taking out of my heated propagator immediately after germination.
I grow the tomatoes the same way every year, pot up using commercial potting compost and then some potted on in bigger pots and the rest planted out in the soil beds. I never feed until the first truss has pea sized fruit and then I feed once a week, but the damage seen in the photos was long before that stage.
I live on a very narrow peninsula and what farming there is consists entirely of traditional cattle out in small 1-2 acre fields.
The only application on the fields is an occasional lime dusting and a annual scattering of a general grass fertiliser.

As a comparison, here is a photo of my this year's conservatory tomatoes, in exactly the same spot as last year, grown exactly the same way I've grown them other years, except using a different potting compost.

Toms.jpg
Toms.jpg (159.39 KiB) Viewed 56 times
Tony

Disclaimer: I almost certainly haven't a clue what I'm talking about.

Weedo
Barbara Good
Barbara Good
Posts: 125
Joined: Thu Jun 30, 2016 4:47 am
latitude: 35.0886S
longitude: 147.1289E

Re: The perils of bought potting compost

Post: #289459 Weedo
Tue Apr 25, 2017 10:58 pm

Thanks Odsox, I think I know the culprit (at least the 2 chemical groups it would belong to) and it is a medium term residua that would remain in untreated green materials. I was a little thrown by the term "compost" as I would have expected the heat processes to breack most of it down - if the term is applied to "potting mix" it would contain both compost and other less treated materials that are more likely to retain the residuals.


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