There's room for a cubic foot of soil in the top of the sterilizer
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I've had a question from India, from a Mr Sondhi,
asking where he could buy a soil sterilizer, like the one that I've
mentioned in this diary.
This Camplex Soil Sterilizer, was my dad's. Although
it dates from the 1960s it still works well. |
There's a kettle element
in its base
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Cooking up Compost
I find that steaming the soil for 15 or 20 minutes kills all the
weed seeds. I wouldn't bother doing this when I'm mixing ordinary
potting compost - I just pull the weeds out as they appear - but
it's essential when mixing seed and cutting compost. The steam also
kills some bacteria.
A foot square (30 cm) perforated metal sheet (right) supports
the soil and allows the steam to rise through it. There's a hole
in the lid to allow the steam to escape.
I love that promotional plastic ruler! (c. 1970?)
|
 |
Homemade Solar Soil Sterilizer |
based
on a design by John Detka (see link
below) |
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|
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| 1.
Put a layer of crumpled newspaper two to three inches (5 to
8 cm) deep in the bottom of a large cardboard box. |
|
| 2.
Place a smaller cardboard box inside and fill the 2 to 3 inch
cavity between the two boxes with more crumpled newspaper, tightly
packed. |
|
| 3.
Cover the gap around the top with folded card and line the inner
box with aluminium foil, using a non-toxic glue. |
|
 4.
Paint the top rim of the box with matt black paint or cover with strong
black paper. You could try painting or covering the sides too, to boost
the absorption of heat from the sun.
5. Use a sheet of clear plastic as a lid.
6. Put your soil inside then use duct tape around the
edges to hold the lid in place with an air-tight seal.
7. To destroy weed seeds, the soil should reach a temperature
of at least 180°F . The oven should be capable of reaching 275°F.
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Note: I've never tried
making one of these; once you've worked out the principle
of the solar oven you'll be able to make your own improvements.
If you do try it, please let me know how you get on.  |
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Link
Making
a Cardboard Box Solar Soil Sterilizer by John Detka
(after a design by Barbara Kerr, 1976)
Soil
Sterilizers at Pro-Grow,
Wisconsin
Richard Bell, richard@willowisland.co.uk
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