On Tuesday, September 6, 2016 at 1:56:31 PM UTC-4, Danny D. wrote:
On Tue, 6 Sep 2016 09:53:42 -0700 (PDT), Cindy Hamilton wrote:

Forget your own soil.
Buy enough of this to fill the planters:
http://www.miraclegro.com/smg/goprod/miracle-gro-moisture-control-potting-soil/prod70262?locale=en_US

I was remiss in not mentioning the whole point is to teach the kids.
It's best to teach them using their own stuff.
That's why we're using "our" soil.
And that's why we're using "their food waste".

Sure, we could buy seeds and buy potting soil; but that defeats the
scientific purpose.

Yes, it'll cost you money. But it'll idiot-proof your grandchildren's
gardening experience.

It's ok if we fail - but it's not OK if we don't understand WHY we failed.
We want to understand the soil first - which is my main question.

Then, we want to understand how to improve the soil second.
That's my second question.

If you cheap out and try to add fertilizer to gravel, failure is guaranteed.

Ah, this is the second *assessment* of the soil pictures.
The first assessment was that it was "crap" and your assessment is that
it's "gravel".

I certainly would agree that half of it is "gravel"; but I already sifted
out that half, so, now it's all *not gravel*.

Is the not-gravel which is left still *gravel* in your eyes?

Well, it's not what I would call a prime growing medium for plants.

Organic matter is required for plant growth. There's symbiosis among
plants, soil bacteria and other organisms, and dead plant matter in soil.

This is a key point!
I don't *see* any organic matter in this soil.
Would I normally be able to *see* organic matter in decent soil?

NOTE: Back east, years ago, I remember the black soil full of bugs and
roots; but *this* soil is not that way at all. Very brown. No roots.
Dunno if that's a clue (but it probably is).

It definitely is.

How do I get *organic* matter into soil?
Do they sell organic matter as such?

I just googled "compost near me" and got some reasonable hits. I
live in the lush environs of southeast Michigan. Our municipalities
collect yard waste (which is illegal to dump in landfills here), compost
it, and sell it back at a reasonable price.

A user-friendly description of this is available in the novel, "The Martian".
Heh heh ... funny you mention this because the *movie* with Matt Damon is
partially what inspired this experiment.

We want the kids to understand their own soil, their own food waste, and to
understand how to improve their own soil to grow their own food.

It's a learning experiment. Failure is an option, but not learning is not
an option.

So, that's why I asked for an *assessment* of the soil that I pictured.

It's hard to tell from a picture. I'd definitely try the county
extension service.

You certainly should be able to see stuff that clearly used to be plant
matter: leaves, twigs, and random partially rotted dross. Evidence
of insects is also good. If worms don't find it congenial, then plants
won't, either.

Amending soil with organic matter involves rounding up a bunch of
composted plant parts and mixing it in. Gardening in containers
is tough (harder than Mark Watney made it sound), which is why
I suggested buying potting mix. Too much water, and plants die.
Too little water, and plants die. The organic matter acts like a
big sponge, and is loaded with soil bacteria.

I've got pretty poor soil; a couple of inches of topsoil over 12
feet of clay (not the caliche of the Southwest, but still pretty
heavy). Every year I plant a few dozen heads of garlic. I've
got two frames that I made from untreated cedar fence pickets,
so they're about 3 ft by 6 ft by 6 inches. I plop them down
in the garden, fill them with topsoil and compost that I bought
in big bags from Home Despot, use a garden fork to mix it with
what was left from last year, and poke in the cloves of garlic.

Sorry, I'm getting a little "stream of consciousness" on you.
It just occurred to me that if there wasn't already anything
growing in your soil, it's very unsuited to your purpose. It'll
take a whale of a lot of amendment to get it to grow heavy
feeders like vegetables.

Best of luck.