Toledo, a climate that is very similar to the climate on the family hunting camp / blueberry farm in southwest Michigan. If you ever get over to the South Haven, or Kalamazoo area, If I'm on the farm then, drop in.
About zero nitrogen fertilizers. These are a pet peeve of mine, in that their use really should be discontinued. Long explanation, but if anyone recommends zero nitrogen fertilizers they did no research. That is a now debunked left over from research done for vegetables and perennial outdoor flower beds at the Royal Botanic Garden at Kew, England way back in the 1880's. The results observed were valid because at that time London had a major smog problem from people heating homes with coal. All the nitrogen needed was being deposited by acid rain, rain pulling the various nitrates, and sulfates out of the smog as it fell. So yes, if you have heavy smog, you don't need nitrogen. BUT if you do not have heavy smog, if acid rain is not an everyday issue, you MUST add nitrogen to keep your fertilizer balanced to the needs of the tree. Michigan State University, Lansing has a series of articles published for the wholesale potted plant industry discussing plant nutrition. All plants need the same nutrients in the same relative proportions year round. The total quantity needed varies with temperature, growing season, but regardless of season they need fertilizer that is roughly 12-1-4, this is ''balanced'' in terms of what the plants use. If a person took as much Vitamin D as Vitamin C the Vitamin D would kill them. The plants do not use all nutrients at the same rate, so a 10-10-10 fertilizer is NOT balanced. A 12-1-4 is balanced.
Once caveat. Potassium is actively used to absorb nitrate, NO3-, and many modern fertilizers use all nitrate as the nitrogen source instead of using ammonia, or urea. In this case an all nitrate for nitrogen fertilizer should be about 12-1-12. This is a balanced all nitrate fertilizer formula.
Unless you are in a continuous feeding program, or a hydroponics set up, in which case, even if you are using a nitrate sourced fertilizer you should use a 12-1-4 to prevent excess potassium from stalling out growth.
Hope this helps. I do have references PM me if needed.