Soil and water chemistry can also have a big impact on leafy garden vegetables: lettuces, spinach, choi, chard. It was a good read, I would have liked it to go into more regional detail but I'm sure there is material out there if I get a bug in my head about it. Ag colleges and universities in production areas will no doubt have done signifigant study and experimentation.
PS: Got me interested enough to look into tobacco seed. Rabbit hole...