I planted some places that were a bit low on calcium and phosphorus and when I planted the seed I put down some gypsum and bone meal.
Both of those will add Calcium, and Bone Meal will add Phosphorous.
It helped them out some I think. They looked really good the first couple of years, but have not made a whole lot of progress since then. Still quite small.
I put down gypsum on them each spring, but not sure it has helped a whole lot in those locations.
I have other locations that had better Ca and P soil test, and had some wild seng growing there already, and that is where my plantings have done best.
If the location and soil is not quite right, and there is no wild growing there naturally... I think it is sort of a long shot that you will have much luck.
I hope yours does well... but I would advise anyone not to go to big at it in questionable locations, until you see good results in year 3 or 4. If they are making 3 prongs and starting to produce berries in year 3 and 4... then I think you have the green light to go all out.
Good luck !
TNhunter