Grape Stumps, Gophers, and Nitrogen Solutions in Hugelkultur Bed?

I'm in the process of building my first hugel bed in an open west facing area in northern California. I've used scrap wood from around the property as well as partially decomposed grape vine stumps. I wonder if anyone has any positive or negative experience using grapes? Gophers are also a concern of mine. We are quite inundated and I'm worried that because I am not using large hardwood chunks that they may burrow up through it. Has anyone dealt with this issue before? The soil in the area is apartial clay. I dug down 4" in the area where I'm putting the hugel and am using the clay soil as my first layer to keep the wood together, pushing it in open spots between the layers of wood. This is actually working out quite well, and I think it will help potential erosion issues I've read about. My idea is to then cover that with leaf mulch from some near by shrubbery and die off from my tree collards, possibly another layer of soil (from where I plan to do a keyhole garden behind the hugel) then plant fava beans or something else nitrogen fixing, until I figure out what to plant in April. I may be able to throw on some chicken manure but it will most likely not be composted in time. My concern is nutrient availability for annual crops and perennial seedlings if I intend to plant this spring (3-4 mo. from now). I do not wish to bring in any material from outside the property. Any insight or ideas would be greatly appreciated. I also wonder what the average thickness of soil and other matter people tend to put on their wood piles. Thanks! Ashley

Not too sure how high you are going to make your hugelkultur bed but you are going to need alot of soil. The soil will have to fill the space between all the wood. Keeping in mind 1/2 the soil you have on top is going to settle and find its way down into the hugelkultur. I would guess that hugelkultur if packed properly with wood would need 1inch of soil/manure/compost for every 4inch of wood.
Give it a try and tell me how high you bed ended up with 4inches of soil after 3 deep watering.

If you add manure I would not be too worried about N-fixing plant. But it does not hurt to add more.
As for the gophers I dont think that they will like the hugelkultur any more or less than other areas.
However I have no experience with gopher (fingers cross), hopefully other with more experience will chime in.