Posted: 13/08/2014 at 15:00
I am surprised in some ways that the apples are perfect, magnesium deficiency goes hand in hand with Bitter pit (Calcium deficiency). Still, how much is more difficult, Never had to use it myself. The recommended dose as a foliage feed is 1 tablespoon to one gallon of water for each foot in height of the tree. Work that one out!
I would also suggest that you test the pH of your soil as that can effect the uptake of trace elements from the soil.
Best of luck!