Hi Allan -
Here is the excerpt on sand from the publication itself. I think
it explains it pretty good and brief. I once made the mistake
of purchasing fine sand for greenhouse production instead of
course sand, and you definitely want the course type for
improved drainage etc.
Want to try something interesting with potting mixes? See my
slides on organic greenhouse vegetable production; starting on
about slide 43 is the shallow bed method of production for
raising sprouts in a greenhouse and for produciing transplants
outdoors; i.e., those are Russian farmers laying plastic on the
ground, it is then covered with about 3 inches of a manure or
compost-based potting mix, then seeds are sown via dribble
or broadcast; thus you can raise thousands of bare root
transplants in a small area without the hassle of plastic plug trays
to one day dispose of; a secret revealed, though not commonly
done, is that you can also raise certain crops to maturity and
never transplant out of the shallow bed; e.g., lettuces, greens,
beet tops, etc... and if you stake the plants up, you can also
do shallow bed production of tomatoes, peppers, and cukes;
altogether, an intensive method of production in a small space.
I believe the Russian farmers used aged manure, sawdust, and
sand. Wood is an abundant resource up north, and sawdust
was commonly used in potting mixes / shallow bed mixes.
In my view, a geotextile weed barrier would make a nice
ground cloth as an alternative to plastic mulch; thus, another
use for super low-maintenance weed barriers in agriculture.
Organic Greenhouse Vegetable Production slides [2960K PDF]
http://ncatark.uark.edu/~steved/ogvp-print.pdf
Interestingly, the Russian farmers were *totally* into the Mittleider
method; one of the farmers had attended a Mittleider workshop
and that is how they went about organizing their approach to just
about everthing: bed production, plant spacing, fertilizing,
greenhouse design, etc. They were doing truck farming on
a 6 bed + drive row + 6 beds pattern making up about 10
acres, and those shallow-bed-raised-bare-root transplants
were hand transplanted into the field using a marker stake
to set out twin rows of broccoli, cauliflower, beets, etc. If you
live in Alaska, on a parallel lattitude with Russia, you know
that selection of crop variety adapted to *long* daylight
conditions is critical; otherwise the cole crops will button, and
that sucks more than a elephant getting a drink of water after
a hot day on the Zambezi Plains. A garden rake, perfectly
sized in width, was used to create a well in the center of the
bed running the full length of the field, thus creating a grow bed
and also to create a reservoir for irrigation. So the Mittleider
method goes beyond soilless grow boxes, which is what you
get by looking at books like More Food From Your Garden,
though I know a few hoop house farmers who still find those
books doublely inspiring as an early model of hoop house
production.
The Mittleider Method -- Food for Everyone Foundation
http://www.growfood.com
Best,
Steve Diver
Excerpt from Organic Potting Mixes for Certified Production
Sand. Choice of sand in a growing mix can make a difference.
Coarse sand -- called builder's sand -- adds air space to the
potting mix. Fine sand settles into the spaces between other
ingredients and makes a dense mix that tends to exclude air.
Clean, washed sand has a near-neutral pH and little if any
food value for plants. Sand is much heavier than any other
ingredient used in potting mixes. The added weight is good
for tall, top-heavy plants that might blow or tip over, but
it is not the best choice for plants that will be shipped or
moved a lot. Sand is the least expensive and most
readily available larger particle material.
