So.....does what I do count as foliar feeding???
I mix up a big batch of blue Kool-Aid/witch's brew (Jacks 20-20-20, ProTekt, Superthrive) and just fill my Japanese copper watering can and water the whole tree, leaves, roots and all. The leaves do take on a bluish cast. Seems to work for me and is completely anecdotal of course. Also, is it really the foliar part or the roots that is more effective? no way to know in my case.
Also, the amounts that remain on the leaves turning them bluish may just be a reservoir for the next few days [as I only fertilize once a week (if I remember..)] as I normal water (again leaves and soil, the whole tree) and perhaps some of that dried up fertilizer is washed off the leaves and dripping on the soil and may be adding to root uptake of fertilizer anyway. I'm not sure if I really need to know exactly what percentage goes in through the roots versus the leaves because I don't think it matters to me...