how to sterilize soil

ellenrr(7a)May 9, 2013

someone told me I could get rid of weed seeds by baking the soil in an oven.
Anyone know how to do that?

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Put the dirt in a covered baking dish at about 200F for a couple of hours.

    Bookmark   May 9, 2013 at 12:12PM
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And be prepared to hold your nose and turn on every exhaust fan in your house! Baking garden soil is a very smelly activity. I only did it once! Much easier to purchase potting soil to start seeds or for indoor plants. And for all other gardening purposes it's not necessary or desirable to sterilize soil.

I've heard you can sterilize soil outdoors in your BBQ but you'd have to google for instructions for that. At least the odor would be outside.

    Bookmark   May 9, 2013 at 1:53PM
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Depending on the volume you want to sterilize, "solarization" might work.

You need a full sun, preferably hot day. The soil should be well moist, but not wet. You put the moist soil in a large clear poly bag, close and seal the top (tie it up), then then lay it flat in full sun. You can poke a probe/dial thermometer through the bag into the soil to get a temp reading. If the only interest is killing weed seeds, then you want > 145 ðF / 63 ðC for at least three hours. If it will get up to 160 ðF, then pretty much everything living will be wiped out. If the soil is dry when you heat it, the majority of seeds will survive.

    Bookmark   May 9, 2013 at 3:43PM
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I think someone mentioned using their barbecue versus their oven. Never done it myself as I have a soil sterilizer.


    Bookmark   May 9, 2013 at 8:56PM
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So, Lloyd, how long does it take to sterilize one of those windrows in that thing? ;-]

    Bookmark   May 9, 2013 at 9:34PM
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weird ... correcting a misplaced post

This post was edited by TXEB on Fri, May 10, 13 at 12:11

    Bookmark   May 10, 2013 at 2:40AM
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feijoas(New Zealand)

Ellen, what's your reason for wanting to sterilise weed seeds in the soil?
I assume that sterilising soil will also kill off the microorganisms...
I mulch thickly, and weeds don't generally make it through.
Some direct-seeded things like carrots aren't mulched, but the area's pretty small.

    Bookmark   May 10, 2013 at 4:24AM
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You can sterilize your soil in the oven, if you are prepared to have your house smell pretty bad for several days. Set the oven for about 200 degrees and bake the soil until the soil temperature reaches at least 180 degrees. You could also pour boiling water over that soil, a bit more dangerous but less smelly.
Sterilizing your soil will kill off the Soil Food Web as well as any unwanted seeds that might be there. A much simpler way to prevent them from germinating is to cover the soil with enough mulch to keep those seeds from getting the sunlight they need to grow. Sterilizing soils is of less importance for most of us then it would be in a commercial greenhouse.

    Bookmark   May 10, 2013 at 6:42AM
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toxcrusadr Clay Soil(Zone 6a - MO)

Unless you have a very small patch to work with, you're going to be at it awhile. And if it's just a small patch, you can pull the weeds before they re-seed, much more easily than baking all that soil. Besides, you'll end up with a soil pretty much devoid of microbes, which will take awhile to recover to a fertile state. If you do end up baking it, add some good fresh compost when you're done. But I wouldn't recommend it except under extreme circumstances.

I tried to sterilize potting mix once and it drove me right out'da house. :-p

    Bookmark   May 10, 2013 at 11:12AM
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nil13(z21 L.A., CA (Mt. Washington))

A huge pot out on the patio filled with soil and water boiling away over a propane burner will kill most everything, but for total sterilization you need a pressure cooker, or autoclave, capable of 15psi. I don't see any reason to sterilize soil though. I only every sterilize starting media and then only for the tougher stuff like fern spores.

    Bookmark   May 10, 2013 at 11:30AM
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Back to the question about getting rid of weed seeds. You can also "sterilize" (mostly) soil in ground via solarization. It takes sun, warmth and some time. Linked below is a Pest Note from UC Davis on how to do it. I'll add (they mention) for smaller volumes you can do both in containers as the illustrate as well as bags.

Here is a link that might be useful: SOIL SOLARIZATION from UC Davis

    Bookmark   May 10, 2013 at 12:15PM
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Lloyd: "" I have a soil sterilizer.""
Is there anything you don't have, LOL?
Anybody knows how long to do it in the microwave? I have done it once but it was a long time ago. It didn't smell but mind you, it was new mix that I needed to germinate rather hard to get seeds. Now I need to do it again but forgot how.

Here is a link that might be useful: FOUND IT!

This post was edited by otis11 on Sun, Aug 18, 13 at 13:45

    Bookmark   August 18, 2013 at 1:17PM
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