Did you mix the wood chips in the soil? My first thought would have been that the wood chips would have resulted in less nitrogen to be available and thus less growth. It would be interesting to see the same comparison in a year from now.
Location: Bay Area CA zone 9
posted 7 years ago
The wood chips were dug into the soil. And wood chip mulch was used on both parts of the bed.
Fava beans fix nitrogen, so nitrogen depletion wasn't a problem.
I saw this same effect last year growing vegetables. Plants grew much, much better in beds with wood chips dug into the soil.
You just need to give it enough fertilizer to overcome the nitrogen depletion.