Soil is akin to a living organism, called the Soil Food Web, which is present in the soil. This takes composting organic matter (i.e. mulch) , moisture and air, then with the help of bacteria, nematodes, insects, worms and fungi. The fungi include Mycorrhizal fungi that symbiotically help tree by extending there root system.
Dirt is dead soil or soil seriously depleted of the Soil Food Web, it typically has no organic matter composting into it and can be compacted. It is very difficult to establish plants in dirt, unless inorganic fertilisers are used to replace the Soil Food Web. If compacted it will also need to be aerated. Once a soil is fertilised it is more problematic for the Soil Food Web to become established (even with composting organic matter), as it upsets the Soil Food Web.
We can aerate soils and add the complete Soil Food Web (apart from insects) and mulch to provide the best environment for your trees. This can be installed to existing trees and as trees are planted.