Sea Shield...a certain cherry grower uses 65 gallons per acre per yr. he also chucks a bunch of the shit that does not pass the screens on the ground. As far as I know no upper limit has been found. You can safely use a 1-3% solution. Personally I would use 1% more frequently.
It does lack Ca though. So I always use soluble gypsum with it
MAP is not an unreasonable choice. If you go that way add as many lbs of humic as you do MAP
I guess this is why people just throw on chicken manure or bio live and call it a day.