Here's a quick comparison of fava beans growing in a hugelkultur bed. The beans were planted in November, about 4 months ago.
The bed pictured, just beyond the fence, is 12'x3'. The 4' of the bed on the right was my first attempt at hugelkultur. It has mostly horizontally buried logs with no wood chips dug in. The rest of the bed was dug with vertical stumps and wood chips.
No fertilizer was used.
Notice how the fava beans grew much better and thicker in the part of the bed with wood chips and vertical stumps.
Here's a closeup of the favas in the vertical stump & woodchip part of the bed. The stalks are much sturdier and thicker here.
Here's a closeup of the favas in the mostly horizontally buried log portion of the bed.