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Sterilized Soil a Bad Idea?

Posted by SteveHillage BC (My Page) on
Tue, May 27, 14 at 21:53

Hi. New to garden forum. New to gardening.
I have so many questions.

I buy pre mixed soil. It's called Island's Finest All Pupose Potting Mix.

I believe it is sterilized and I heard some where soil sterilization can be bad if you use compost because it kills the essential bacterias needed to break down the compost.
Is this true? Organic fertilizer is a must for me, should I continue using sterilized soil?

Thanks


Follow-Up Postings:

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RE: Sterilized Soil a Bad Idea?

Starting seeds in sterilized soil is fine, but after the sterile soil joins compost it will add goodies to your sterile soil, but won't hurt the compost.


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RE: Sterilized Soil a Bad Idea?

All potting soil gains microorganisms over time. They blow in. If you'd like, you can hasten this by going outside, getting one pinch of good soil, and dropping that one pinch in your pot-plant.

Most people are not aware that there are literally millions of "critters" in each gram of soil, which equates to about a good pinch of soil. These "critters" are bacteria, actinomycetes, fungi, yeasts, protozoa, algae, and nematodes. They are microscopic organisms that live in the soil. It sounds terrible, but we exist today because of them. They are what give the soil life, which is necessary to grow plants, the backbone of our existence.

- Steve Jones, Master Rosarian


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RE: Sterilized Soil a Bad Idea?

Is this potting soil or "garden soil" you are referring to?
Potting soil is not soil but is a growing medium made of peat moss, coir, or finely ground bark, or a combination of those and the Soil Food Web will not be present in that for quite some time. That is one of the reasons many organic growers do not consider container growing to be organic.
Sterilizing garden soil could kill off most of the Soil Food Web which would mean time would be necessary for them to recover, a long time, like years, although putting good, unsterilized compost into that soil might help.


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RE: Sterilized Soil a Bad Idea?

There will be more microbes in fresh compost than in soil, and if you mixed compost into sterile organic matter the microbes will grow and spread. I don't think potting mix would actually be sterile, it looks like the finer bits are already composting so there must be microbes in there.

If you're just transplanting flowers or veggies into pots or containers, you certainly don't need sterile medium. Actually, microbes do a lot of the work of managing nutrients and feeding plants.


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RE: Sterilized Soil a Bad Idea?

kimmsr, I posted a study a little while back ... ah, here we go:

Seedlings were germinated in seven different sand- or soil-based and artificially based growth media. Seedlings grown in the HFC had fewer mycorrhizal short roots than those grown in the open greenhouse atmosphere. Furthermore, the proportion of seedlings from the HFC that were completely non-mycorrhizal was higher than that of seedlings from the greenhouse atmosphere. Seedlings grown in sterilized, artificially based growth media (>50% peat moss, vermiculite, and/or perlite by volume) had fewer mycorrhizal short roots than those grown in sand- or soil-based media.

Leads me to believe it happens fast. (The study is actually about reducing the effect, in order to maintain truly sterile conditions. They have to use "a high-efficiency particulate air-filtered chamber" ti achieve that.)

(The hat tip at the end to "sand- or soil-based media" is a bonus of course.)

Here is a link that might be useful: airborne ectomycorrhizal fungi


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RE: Sterilized Soil a Bad Idea?

Soil is terribly hard to truly sterilize, BTW. I used to work in a lab doing biodegradation studies on pesticides in soil. We were supposed to have 'sterile control' samples to gauge any non-biologically mediated degradation. We'd sterilize the soil in an autoclave, and the samples were incubated in sealed sterile jars, but after a few weeks there were always bacteria in the sterile ones. Fewer of them, but still a lot - maybe 10,000 per gram compared to 10 million in the unsterilized soil. I think you'd have to autoclave it several times, days apart to really kill it.


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RE: Sterilized Soil a Bad Idea?

I've spent a lot of time reading posts on Garden Web and some of the people posting here are pretty informative. Unfortunately, and it's not limited to this forum or these posters, but most of the time people don't answer people's questions.

Your answer: No, sterilized soil will not kill off bacteria added to it.


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RE: Sterilized Soil a Bad Idea?

"should I continue using sterilized soil? "
It is not necessary.


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RE: Sterilized Soil a Bad Idea?

It is actually unclear if the OP is mixing anything, or referring to the organics in their original mix as "compost."


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RE: Sterilized Soil a Bad Idea?

Upon rereading the OP's question I think the issue is actually whether the lack of microbes in sterilized soil (or potting mix, etc., doesn't matter) will result in an inability of that matrix to continue breaking down organic matter (compost) added to it. I would say no, because compost has loads of microbes of its own. I hoped that my statements about potting medium containing compost and it being nearly impossible to really sterilize these materials anyway, would have made that clear but perhaps not.


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