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debstuart1

solarizing soil - how long to leave on?

debstuart1
17 years ago

I am extending my holding bed and decided to solarize the area before I transplanted things into it. It has been under plastic, sealed off well, for about six or seven weeks. I would like to uncover it now but wonder if this is long enough? It gets sun most of the day. I did black plastic with clear plastic over it.

thanks

Debora

Comments (4)

  • rhizo_1 (North AL) zone 7
    17 years ago

    By putting the black plastic over your bed, you've nullified the ability of the sun to heat up the soil enough to SOLARize! Sorry. Solarization requires sunlight penetration + moisture + time. No sun=nada.

    Your black plastic treatment may be enough to kill some vegetation (by sunlight deprivation) but will never, ever create enough heat to kill weed seeds, fungal organisms, nematodes, etc.

    The good thing is that perhaps this bed didn't need solarization, anyway. What were you trying to accomplish?

  • debstuart1
    Original Author
    17 years ago

    Sorry to be so long replying...Here's what I thought: I read that yes one should use clear plastic which I did, but also that it would be even more effective if there was also black plastic to use as a kind of heat sink (The clear is on top). I am making a holding bed and I know the small area has lots of weed seeds, as it's adjacent to an area where I did the same thing without solarizing. So I thought I'd do this as prep. It's not a tragedy if it doesn't completely work, but it'll be a great time saver if it does. Has anybody else heard of the two plastic approach??

    Deborah

  • debstuart1
    Original Author
    17 years ago

    Follow up...

    Well, we took the plastic off and things are looking good. Of course it'll take into next spring to really know. I have planted the bed up with daylilies and iris which I have thinned out and hope to sell next spring or trade. I took good care not to dig around, both so I wouldn't unearth deep weed seeds and also to preserve soil structure. I just put about 2 inches of good absolutely weed seed free compost right on top.

    Here's hoping! I'd still like to hear from others who have solarized successfully

    Deborah

  • rhizo_1 (North AL) zone 7
    17 years ago

    I have. And the process does not include black plastic. You've heated up your soil, mostly on the surface, and the air space between the clear and the black plastic. That 'heat steaming' effect can't be realized without the sunlight penetration into moist soil. This is called radiant heat.

    An inexpensive soil thermometer would have been a good little tool to use in your experiment. ;-)

    You might have been able to get the surface hot enough to kill some seeds resting on or near the top of the soil, but not to penetrate to much more than an inch or two (if that). Soil is a remarkable buffer against heat.

    Oh...there IS a 'two layers of plastic' approach. Two layers of heavy mill CLEAR plastic will do a much better job than on layer.

    Here is a link that might be useful: Soil solorization