Why mulch especially woodchip can be a problem if used incorrectly.
The two problems are acidity and nitrogen fixing which you may find in a woodland also. This is due to wood or harder organic matter decomposing under the soil where microbes take longer to digest the material causing nitrogen to be used up and acidity to increase. Alike to our stomachs.
The main solution comes with keeping the woodchip on the surface of the garden and not mixed in.
This comes from experience and the 4 hour version of the back to eden garden video as the shorter videos can seem misleading without the full video.
This is also why in a ‘collective garden’ there are layers and gradients of decomposition. The woodchip sits on compost not soil, I.M.O (microbes) are added, the woodchip has started to decompose prior to purpose, is sifted and is never mixed into the garden.
The main example i have seen of this mistake is on a big scale where woodchip paths between rows were cultivated into the garden and re-ridged causing extremely little growth in the garden from the next year onwards. The solution in this case would mean heavy fertilising and lime for a long period of time or re-purposing the plot
(Perhaps to an orchard or raised beds with brought in soil and compost).
Treadit Gardens 