Interesting ideas about using drywall. Gotta ask, what else is used to make drywall? Just wondering if any other ingredients could impact plants or fruit. Remembering from years ago all that drywall from overseas that was making people ill in their homes. Seems there was more than gypsum in that stuff.
Its just gypsum,water and paper in the big sheets.
But the square ,small size plates used for ceilings do contain chopped fiber glass.
There are also big sheets that are thin and bendable wich also contain fiberglass( you can recognise these because they have no paper on them and on cloose inspection you can see the hairs like looking fiberglass).
Also ,drywalls from demolition that are painted ,contain various types of paint and somme paints can have antifungal chemicals added to them .
Probably mycorrhyzae wont like them.
Best of the best and its also dirt cheap ,is to use fresh gypsum,not hardened stuff like those expensive bags wich are same like the garbage from constructions.
Fresh,non hydrated gypsum mixes with the soil and acts like a weak cement maintaining the soil loose after you tilled.
Its good to fix soil that gets compacted and cracks.