December 18, 2015
It was a couple years back that I played with the combined
use of greenhouse film and Agribon 70 fabric.
Over the years I have found that fabric protects from cold
and also lowers day time highs. My thoughts were to create a temporary green
house that would not need to be vented on sunny days during the winter. Most
winters the sunny days coincide with windy days. Opening a greenhouse on such a
day, you could find the cover in Midland or Mexico depending on the wind
direction. It was important to do this without having to vent the structure.
I tried three different configurations to see if this idea
was plausible. In order to have something to compare it too I used a bed of
chard that was covered like I normally do, with 2 layers of agribon 19,
(Control). I used a remote thermometer to record temps.
The three beds were: just greenhouse film (only), Agribon 70 under greenhouse film (under),
and Agribon 70 over greenhouse film (over). On a cold night (11.8 degrees),
both the only and under recorded temperatures in the teens and the over was in
the twenties. Then on a 60 degree day both the only and under were in the upper
90’s and the over was in the mid 80’s. When the outside temperature got into
the 80’s both the under and only were up to 120+ degrees and the over was
around 100.
I only entered the structures to harvest and water,
otherwise it remained covered. Only 2 of the beds were planted with chard, the
control and over bed. Before I started my experiment the over bed was exposed
to severe freezing weather and did not look very good. It looked better after
it was pruned and cleaned up. Every two weeks I harvested the control and the
over bed. I harvested both of these beds on the same day and weighed the
harvested quantities. .
The results were really quite interesting. The first 2 weeks
more was harvested out of the control than the over, but I was seeing re-growth
in the over bed. By the second two weeks the beds were very similar in harvest
quantities, and then by the third two week period the over bed was out
producing the control. Shortly after the third two week period is when the 80
degree day occurred and I stopped the experiment.
To say the least I was very pleased with the results. Last
year I was going to try some more beds to see if I could replicate my results.
In order for passive greenhouses to work, you need sun and last winter remained
quite cloudy.
This year is looking better. The day time highs are getting
into the 60 degree range with the nights in the 30’s and 40’s, and not to
mention abundant sunshine!
Next week why the
need.
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