Answer: That is an interesting question and is something I have never heard of! I would imagine the idea behind it was to add some minerals to the soil but they won't dissolve any time soon in water so that wouldn't be helpful in any immediate sense. Sometimes they are recommended as a deterrent for slugs, but in that case they are crumbled and sprinkled on the soil surface. I think it would be better to add the eggshells to your compost pile and then use the compost.
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