True Living Organics - The Ultimate Guide to Growing All-Natural Marijuana Indoors (2012)

Here are two types of oyster shell; ground on the left and crushed on the right
Much like phosphorus (and all other mineral elements particularly), calcium must be released
more slowly to match the speed at which the roots can actually absorb it. The goal in TLO is not to
cram nutrients down the plants’ throats. Too much calcium, or phosphorus, or anything else, basically,
is a bad thing. You cannot “fix” problems by just pouring more of any particular additive into your
plants’ containers. It is best to provide the calcium in TLO from multiple sources, like bone and bulb
food, feather meal, lime, and oyster shell. This is how I do it.
REV’S TIP
You have to look a bit for oyster shell products. I love the Down to Earth
brand of ground oyster shell (also known as oyster flour). Since I live on
the coast I also have access to crushed oyster shell, which is just a very coarse grade version of
the ground shell. This stuff is fantastic for several reasons; it’s pH balancing, the bacteria just
seem to go crazy with this stuff in the mix, and the worms love it too! It gives a very slow and
steady release of calcium, and it also serves as “artificial reefs” for the microbeasties to attach
to. I would go out of my way to find this stuff, or get a local nursery to order some for you.
Soft Rock Phosphate and Rock Phosphate
Don’t blow off the soft rock phosphate (SRP) and rock phosphate (RP) in your mix. The most
important thing you will want is the SRP, in powdered form, when mixing your own custom soil
mixes involving lime and high nitrogen. The SRP has a sort of magical (magical to me at any rate)
effect on a soil mix when a lot of powerful nitrogen like blood meal and/or bird/bat guanos, are