if garlic has a similar effect on the microbes legumes use, 12 inches seems to be working. My wife had never heard of this advice and planted the garlic in the same beds as the peas and beans. Both of which are growing like mad and blooming already.
Huh, I'm surprised to hear this. My beans grow far better around onions (and other aromatic herbs, such as dill) than they do without them, due to the beneficial predators attracted by the aromatics. I haven't checked the soil microbe levels. I'm eager to hear what you find.