I’m hoping to get some help with some apple bench grafts that we planted out this spring. Things started out generally ok, but about a month ago the growth seemed to be kind of stalling out, and I started seeing leaves curling and getting crispy. This crisping appeared primarily on the new growth, and especially at the tips and edges of leaves, though in the worst instances it seemed to be destroying new leaves before they could fully form. With the help of a link posted by @mamuang, I concluded that what I was seeing was a nutrient deficiency, probably potassium and possibly calcium as well.
Going with that, I dosed the trees with a fertilizer that my wife had picked up for her potted Meyer lemon (Espoma Organic Bloom, a 1-3-1 plus 1% CA formulation marketed for use with fruiting plants as well as ornamentals). I imagine that there are things that might have been more effective, but that was what I had on hand, and in the short term it seemed to do the trick, because I saw a good flush of new, undamaged growth following the application.
About a month out, however, I’m starting to see signs of the crisping coming back on the tips and edges of new growth. So, while things are still doing fairly decently, I figured I would ask for some help in coming up with a longer term solution.
A couple of more details about our situation: the trees are on G41 planted in an area of former lawn that I’ve turned into a temporary “nursery.” They are currently top dressed with aged compost around the trees and mulched with wood chips spread over newspaper between rows. Next year I’m hoping to plant them out to start forming a Belgian fence along the perimeter of our yard and garden. According to the USDA soil survey, the soil type is Hinckley loamy sand, which is described as being sharply draining (especially in the subsoil) and moderately to strongly acidic.
So, here are my questions:
Does the diagnosis of potassium/calcium deficiency make sense? If so, what, if anything, would people suggest that I do to help the trees out either in the short term (this year in the nursery) or in the longer term (preparing/caring for the soil where they will be going in the future)?
Does it seem likely that the other characteristics of our soil (acid, sharply draining) are contributing to the problems that I’m seeing? If so, what steps would you suggest taking to remedy the situation?
I am very new to doing this, so your suggestions are very much appreciated!