crushed oyster-shells

[Andybear]

Can I put crushed oyster shells into my tomato growing soil or will it affect the ph?

[RayR]

Since oyster-shell is mostly Calcium Carbonate, the simple answer is yes it can raise soil PH, but the simple answer doesn't always mean it will since different types of soils have different buffering properties.

Read here about soil PH management

[greentiger87]

What are you putting them there.. for? Crushed oyster shells can be really high in sodium, so watch out for that too.

[RayR]

Originally Posted by greentiger87

What are you putting them there.. for? Crushed oyster shells can be really high in sodium, so watch out for that too.

Oyster shells are right around 95% Calcium Carbonate, the remainder is trace minerals. You would think that if there were any Sodium salts that they would be on the outside of the shell.

[greentiger87]

Well yeah, I guess I could have been more clear. Bagged, crushed oyster shell tends to have a lot of leftover salt residue. I really damaged a couple of potted plants once trying to use it as an amendment.

[RayR]

I think you are right there, in order to use oyster shell in horticulture, they have to be washed thoroughly to remove the salt residue or left outside exposed to the elements for some time and let the rain do it.