These shots are from a while back at one of the botanic gardens in town, under the canopy of a raintree
Albizia saman Curator was concerned about the overall health of the tree, excessive deadwood, live timber badly affected by longicorn beetle damage. In addition to the decompaction throughout the root plate we vertically mulched after a coprehensive set of soil tests.
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I quess they don't really show you much we put the Airknife in along a grid pattern about every 1.5/2m.
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Once the entire area was done then went around and vertically mulched into the holes created, with a mix determined by the soil testing I'd done there. You can see the overspill from the holes marking out the grid patern if you look closely.
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The idea for us is to penetrate down 300-400mm no deeper, especially if you're vertcally mulching since you don't really want to insert organic matter below 400mm in compacted soils.
More often we sheet mulch over the decompaction, this reduces the likelihood of recompaction occuring too soon, as well as providing the best microenvironment for the soil food web (so long as your mulch is the right stuff!!)
I know the science so far has not proved results as positive but I have to say that the plots used in the studies I'v seen don't reflect the reality in the urban forest I work in. Soils are grossly impoverished, heavily compacted very very dry and by a large comprised of fill or inverted horizons, in these conditions decompaction even if it does(and I accept it does) destroy a fraction of the fine root hairs, will have a positive impact on the health of the soil, when combined with the addition of appropriate organic material, and consequently the health of the trees growing in that soil.
We have to get the soil environment right, its the key to everything the soil food web has to be favourable for trees and from that long term tree health will follow..if we can stop people treating them as if they were big hedges!
SF