Use of crushed oyster shells as a soil amendment

[Eric]

What are your views, everyone, on adding crushed oyster shells to the soil? My own thinking is that they would work well as a long-lasting supply of calcium and trace elements without directly affecting soil pH. The alkaline effects of individual flakes would extend only millimetres, if that, so I don’t think they would interfere with acid soil-loving crops like potatoes (pH 5), if a rotation scheme were to bring them to a bed containing lots of oyster shells. On the other hand, I think they would be appreciated by alkaline soil-preferring plants like peas (pH 6.5), since their roots could seek out the shells to benefit from the locally high pH and calcium availability. What do you think?

[charles]

Eric, you are thinking like a chemist, too much. Makes it so complicated.
Oyster shells, brilliant for everything, I know from seeing their use.
Potatoes thrive in my Ph 7.3 soil, your Ph 5 is not true.
Except in extreme soils, gardeners need not worry about precise Ph.

[Eric]

Thanks for your advice. True, I have a scientific background. Well spotted. In several decades of growing vegetables, though, I’ve never measured my soil pH, feeling that it probably doesn’t matter much in a well-tended and healthy soil. However, I didn’t want to add a potentially useful but unfamiliar material to the soil, in spite of the benefits noted in this scientific paper. Less unsure about it now!

[Stringfellow]

Hi Charles. If crushed oyster shells are a good way to increase fertility would they be another valuable addition to the compost heap?

[charles]

Yes a good idea Tris. Should help the shells decompose and spread their goodness.
And thanks for the link Eric.

[Don Foley]

Hi All,

I cant see how Oyster shells would decompose in either soil or the compost bin.
I do add egg shells to my compost bin but only after crushing them up to almost powder.
I dont doubt that they do add nutrient to the compost.
I still find pieces of shell in the soil years after they have been put there.
Im not bothered by this as I see them as a drainage aid.

Don

[Stringfellow]

I figure oyster shells in powdered form will decompose faster due to increased surface area, possibly quicker acting than if coarsely crushed. It’s not something I would go out of my way to buy, but if I came upon a cheap source it’s good to know it will have some value to organic veg growing.

I compost egg shells too Don and also don’t mind that they take some time to ‘disappear’.

[Eric]

Whole oyster shells do seem to take a long time to break down: archaeologists often find buried piles of them, even from as far back as Roman times, but I imagine small pieces would eventually dissolve, at least within my lifetime!

[Author]

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