I have tried alfalfa meal, but not in this formula.
This is probably more than I put in (2 tbsp/gallon) but that's OK, because I don't think I put in enough. It contains a fair amount of magnesium, so I was trying to lessen my need for cal/mag. (Result: don't give up the cal/mag!)
It does not seem to be a hot nutrient source, It didn't cause any burn or anything, so experimenting with it is quite forgiving.