AaronTT

I have used all three, and now prefer gypsum. It can be broken down quicker with added bacteria. I am not a personal fan of bone meal, although it does work if you don't overdo it. I use it when I rarely add phosphorus. I keep phosphorus low, as it can prevent the uptake of other nutrients. If you keep adding the bone meal, over time phosphorus can build up in the soil and cause problems. The egg shells work, but not as good as I originally thought. Some say to cook the eggshells which I have not tried yet. The gypsum, added along with additional microbes, and worked into the soil with a small amount of nitrogen in the form of manure works best for me.
I personally grow 100 percent naturally. I focus on minerals in balance, including trace minerals not often considered such as selenium. In fact I have a few test plants planned for this upcoming season, where I will introduce certain rare minerals into the soil. Last year, I had some really good results with other minerals, which really made the plants look healthy and lush.
I like how gypsum does not interfere with absorption of these trace minerals, if used in the right amounts. Some of the others can change the soil ph unfavorably. Doing so can cause a lockout, and prevent uptake of other minerals.