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Oyster Shell Substitute Ratio

bertbkill

New member
Hi Everyone,

So I am following the rock dust recipe below for my soil mix and the only oyster shell that they sell in my area is not in a powder form but 2-4 mm in size. I do not believe that in a 4 month grow this type of oyster shell will alter the ph of peat moss sufficiently so I have sourced limestone from the source in the link but I wanted to ask if the application rate would be the same as the oyster shell?
coot's mix is 1:1:1 base mix---peat, compost, aeration.

per cubic foot add

1/2 c neem seed meal
1/2c kelp meal
1/2c crab shell meal

1 cup rock dust
1 cup basalt
1 cup oyster shell powder
1 cup gypsum

Limestone%20Grade%20F%20Pulverized%20Limestone%20spec%20sheet.pdf
 

KIS

Active member
Just use agricultural lime. It's widely available and the exact same stuff more or less. Both are a mined product. You should be able to find a 50 lb bag for under $10. Keep in mind you want Ag Lime not dolomite or hydrated lime.
 

J-Icky

Active member
I use the oyster shell they sell for chickens, probably the same stuff you're talking about. You might be surprised how fast it breaks down and it's ability to stabilize your soil. Oyster shell is mostly calcium carbonate so as the soil becomes more acidic the faster it breaks down.

But since you're talking about a 4-5 month period it sounds like you won't be reusing the peat so honestly it won't break down much at all. The only time you really need to worry about peat making your soil acidic is over the course of a few seasons or in tlo gardens.
 
Just use agricultural lime. It's widely available and the exact same stuff more or less. Both are a mined product. You should be able to find a 50 lb bag for under $10. Keep in mind you want Ag Lime not dolomite or hydrated lime.

Hey KIS just wondering why the ag lime not dolomite or hydrated ?
 

Ratzilla

Member
Veteran
Dolomite is magnesium and calcium (calcium magnesium carbonate). About 11% magnesium.

Hydrated lime is calcium oxide or calcium magnesium oxide.

To add
While you need some magnesium in Organic gardening many peeps are getting away from using dolomite lime thinking the 11% magnesium tends to tighten ones mix up.
While hydrated lime moves the pH to rapidly and does great harm to organic soil life.
Ratz :tiphat:
 

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