hi Dimitri, I have no answers but some considerations, I think it all depends on your budget. if I understand correctly you do not use micro sprinklers but drip tape and I think that with the microjet the water would be distributed much better. for the foliar I think that the right way is to focus on increasing photosynthesis as it would improve the microbial community that could make available the nutrients that are missing. have you done total soil tests to see if P and K are present in the geological profile? if the foliars are well designed you will use them less and less as they will stimulate the microbes to do the work for you. I would distribute the compost in the walkways to stimulate the roots to go looking for nutrients