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Re: Solarizing soil

LMann76543@aol.com wrote:
> Isn't it the longer wavelengths of sunlight that more effectively heat the
> soil rather than the ultrashortviolet?  Trying to remember physics...

Hmmm, well yes, and no.

Yes, longer wavelengths (as in infra red) do heat more effectively, or
are at least associated more closely with heat. Thus red orange etc are
the "warm" colors. But, they are reflected more effectively by glass and
plastic (at any refractive index boundry actually) which is also the
reason that solarization works, and why sun shining into a room through
a window heats the room. Long waves are much more effectively reflected
on BOTH sides of the plastic. So the shorter wavelengths (ultra violet)
penetrate the plastic, get absorbed by, and heat the soil and the long
waves (the heat) that radiate back from the soil are kept in by
reflection from the plastic.

Now just to confuse things, micro waves, which are relatively short
wavelength radiation, are used in, TA DA, microwave ovens to heat
things. They are used because they can penetrate and heat from the
inside out as opposed to short wavelengths that are stopped at the



John                     | "There be dragons here"
                         |  Annotation used by ancient cartographers
                         |  to indicate the edge of the known world.

John Jones, jijones@ix.netcom.com
Fremont CA, USDA zone 8/9 (coastal, bay) 
Max high 95F/35C, Min Low 28F/-2C average 10 days each
Heavy clay base for my raised beds.

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