I had not thought of it that way. We tilled the soil often on the farm where I grew up, of course, farmers didn't know as much then as they do now. So, this has me wondering how deep the mycelium network goes into the topsoil. Being in symbiosis with the plant's roots, wouldn't it go as deep as the roots? If so, it seems to me that the depth of tillage and the type of root growth would matter. I am wondering about it because I loosen the top inch or so of the soil around my plants. It gets hard or crusty from topdressing. I think the crusty soil surface reduces aeration and can make watering uneven.