Soil pH on arable is 5.8 - 6.2 lots of potatoes in rotations !Presumably you have deficiency in boron, copper and mag too?
What are you typical ph phil?
Grass land 5.4 - 5.8 !! Farmers treat grass like crap, not a crop
We are deficient in calcium, magnesium, potash, copper, zinc, boron and molybdenum. Soils are high in phosphate but not available to crop as it is not in solution. According many of my colleagues we have high magnesium levels, but when the but the figures through Albrecht they are all deficient.
I used to use a lot of Majik manganese but now use another manganese, not through choice !!!
The high magnesium is antagonising the potash so the application of gypsum or Calcifert S will help strip the magnesium out the soil.
As you will be applying quite a it of sulphur this will antagonise copper, but you have it covered with a foliar feed. Magik manganese with it's added potash will help as long as you put on with every application.
Another option would be Kudos from Headland.
I am busy doing work on potash on soils with indexes of less than one, and trying to update figures for maximum uptake for winter wheat crops in excess of 8t/ha (PDA figures)I am looking at 2 options a 3 year plan to raise to required index in 3 years or the fertiliser company pension scheme, little and often and never raise the index.