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  • From: "Beth Spaugh" <lists AT rhomestead.com>
  • To: "'Market Farming'" <market-farming AT lists.ibiblio.org>
  • Subject: Re: [Market-farming] straw bales as greenhouse heat source??
  • Date: Tue, 17 Jan 2006 19:13:48 -0500

You need to subscribe to "Growing for Market" -
http://www.growingformarket.com/

The Oct 2005 issue had a couple articles by growers who heat or have heated
their hoophouses, and alternative fuels.

The Nov issue has an article on Winter greenhouse crops with info from John
Biernbaum at Michigan State U. Talks about light vs heat. What struck me and
made me go out and put rowcover over the greens in my hoophouse is that
"When the air temperature decreases, moisture from the air condenses on the
fabric. As explained previously, the moisture helps to trap long wave
radiant energy emitted by the soil or plants. Ice forming on the covers and
the plastic helps trap heat. We call this the cloud or igloo effect. We have
examples of temperature outside being 0 to -20F while temperatures under the
cover inside the greenhouse have rarely gone below 15F."

And further down in the article:
" Opening the covers in the morning on sunny days... it is important that
fabric covers are pulled back into place before air temperatures approach
freezing or the damp fabric will freeze together and tear when pulled
apart."

In the Dec issue someone has written in asking about cover vs light for
tomatoes. Biernbaum responded that most of his work was with cold-tolerant
[polyethylene or fabric] greens which are totally different than tomatoes.
BUT, the high humidity with covers may increase blossom end rot since the
plant isn't taking up as much water. And that it may not really matter just
how insulative the cover is as long as there is another cover.

He references Penn State tomato work. Since you are mid-Atlantic, why not
get info from Penn State?

Beth Spaugh
Rehoboth Homestead
Peru NY
http://rhomestead.com

-----Original Message-----
From: market-farming-bounces AT lists.ibiblio.org
[mailto:market-farming-bounces AT lists.ibiblio.org] On Behalf Of Allan
Balliett
Sent: Tuesday, January 17, 2006 3:43 PM


The inner covers don't hold that much heat. What is it? 5 degrees, or
something like that?

And what's a single layer hoophouse? 15degrees, or something like this?

This all becomes very important to me when I think of hoophousing
tomatoes in March in the Mid-Atlantic. It seems to me that 5 degrees
here and 5 degrees there ain't really going to make the difference in
the possibility of a 20degree night. Maybe I'm too flighty with this,
but I'm concerned that the margins aren't there for us.

With brassicas, the cover itself, as far as I can tell, protects us
from the physical damage of frost, and then you also have x degrees
of warmth, from the outer cover and, potentially, from an inner
cover.. With no protection other than the single layer of plastic on
our 40x96 hoop, I have BEAUTIFUL tatsoi and some fairly nice asian
greens (name escapes me) Nice and alive, but I don't think they have
marketable texture. THey have frozen solid a few times. It almost
seems like the tatsoi has NOT frozen solid (never seen it that way),
but that doesn't seem logical.

I'm in the process of building a manure hot box for starting
brassicas, etc, for planting out in March. I wonder if I'm being too
cautious with tomatoes?

Thanks -Allan
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