@ Hasardine:
therefore, no significant damage to the spade !!!
No hasty deductions! The figures indicated are the maximum values in TCF (simplified cultivation techniques), but the ultimate objective remains direct sowing without tillage (say a simple surface scraping).
In gardening, a depth of spade is enough to considerably reduce the soil's pedoflora by bringing anaerobic bacteria into contact with the air and, conversely, by suffocating living animals usually on the surface.
The use of the grelinette allows deep loosening without inversion of the soil layers. Furthermore, after a few years, if enough organic matter is added, the soil dynamics are such that it is worked continuously and no longer requires any loosening work.
Another disadvantage of this type of interventionism in gardening is that one creates the conditions favorable to an "explosion" of weeds.
The more weed, the more we will have to do it: cry:, whereas with minimalist weeding it is easy to quickly forget this kind of constraint.
My garden is sandy, so very "messy", by adopting this course of action, plus a little mulching *, I no longer have any problems.
For example, I do not need to weed my strawberry plants, because when I pick my strawberries I pull (sometimes) the rare grass shoots. They often result, moreover, upwelling due to moles that I have learned to tolerate, or more.
* The earth with horror (if we can say!) Of being naked, on the other hand it needs a nourishment on the surface: a mulch of herbaceous, or better of woody realizes an excellent protection at the same time than surface composting.