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Re: [APD] old soil substrate

But then using one coffee can's worth instead of 20 ought
to be good for one year to five years instead of twenty to
one hundred years? ;-)

If the soil suppplies decades worth of material, then it
seems that the idea with the soil is to have a
superabundance of the chems, but "sealed" down under the
gravel. If so, how much one uses doesn't seem all that
critical. Almost any amount is too much but hat's okay
because it's "sealed" as a *sub*strate.

Perhaps the fizzing out is due to lack of fish food.

Scott H.

--- Jim Seidman <js5 at seidman_net> wrote:
> Scott Hieber writes:
> "Based on Walstad's excellent treatise, doesn't it take
> many years for the
> soil to be depleted?"
> Aren't soils from diff places very diff?<<
> As Ellen said, a coffee-can full isn't much. Actually,
> Walstad explicitly
> makes the point that you can use much more soil (on a
> volume basis) than
> you can many substrate additives, so even if it's a less
> concentrated
> source of a particular nutrient you still wind up with
> more.
> That said, Walstad expects the soil to be a great source
> of traces, not
> macronutrients. I think that Josh Bjork's problem is
> limited
> macronutrients, which in the Walstad method would be
> provided by large
> amounts of fish food.
> As to the differences in soils, Walstad specifically
> recommends using
> topsoil from a well-drained area. While the specific
> composition will vary
> a lot, any topsoil capable of supporting terrestrial
> plants will of
> necessity have certain nutrients in it. Getting it from a
> well-drained area
> also tends to limit how much OM it contains. So yes, soil
> X may have a 20
> year supply of boron while soil Y has a 100 year supply,
> but either one
> would grow plants for a good long time.

S. Hieber

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