You know your soil is calcium deficient in a few ways:
It will grow dandelions that will out-compete everything else (they have a long taproot that will grow deep down to get what they need, and bring it up)
Every time you try to grow a Solanum member of the family (tomatoes or potatoes) they stop growing, go yellow from the bottom leaves, and then suddenly die. Poor things literally starved to death -- they have high calcium needs!
Thank you! Based on this, it seems like there is still plenty of calcium in my soil... for now.