How to start a compost pile
From:
Jack Rowe
Date:
May 07 17:43 UTC
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Hi Robert,
Rock Phosphate and gypsum both come from organic gardening stores, usually
Payne's in SF has them both, also the one on Ruffina whose name is escaping
me... a first application of gypsum might be 10 to 40 pounds per 100 sq ft (I'd
make that decision on how long I'd been gardening in the spot and whether I was
using city water, well water or rainwater... point being salt buildup, with
well water being saltiest and rainwater least... the gypsum acts to counteract
the effects of the salt, which in this context are basically to pull water away
from roots because the salt is hydrophilic... salt is the Southwest gardener's
worst enemy, especially over the medium to long terms). If you've been using
groundwater and gardening in the same spot for 5 or more years, you should be
able to see a visible difference between watering with groundwater and
rainwater (in how much the plants perk up).
Rock phosphate you can add at maybe a cup or two per 100 sq ft, couple cups if
first time and less subsequently. Bone meal would act similarly, but is more
expensive usually and not as long-lasting (on the other hand, quicker to become
soluble if a first application). Too much rock phosphate will raise pH too high
and render itself (and some other nutrients) insoluble. Good organic matter
will lessen/buffer this effect.
Wood ashes should also be used sparingly (same reason, easy to raise pH
excessively) and mostly supply potassium which isn't usually much of a problem
anyway, I'd do a cup or two/100 sq ft.
.