I am using 0.5mm limestone grit from local quarry, have been told to go up to 10mm. All this helps create environment for uncinatum to produce the black fruit. I expect most of the orchards planted in the Uk have a good proportion of the fungi nodules on the root system but the next stage is depended on the environment. Lime is wonderful for encouraging insect , which in turn provides a natural food for the truffle. Also keeps other competing mycroyzia at bay. I am using hebridean sheep to graze around trees at a low stocking rate one to the acre and we have lots of grass in somerset. I used to hunt the hare many years ago and you got the feel of which field she would be lying up ;really its same with the truffle,its a living breathing animal and like's the sort of place we might. I don't think planting truffle impregnated trees in soil with correct ph is enough I think you have to become abit more mad and imagine your a truffle and start to try and create that same environment.