Hi carlson.
One of the concerns using galvanised anything is that the zinc leaches away over time into whatever surrounds it. Stainless is better, as I understand it. Zinc will poison you, your soil, and anything you grow out of it if the levels get high
enough.
My
experience in this vein is in building raised hugelbeets, buried wood and all, but many of the issues are held in common.
My concern, and I have heard this in many places and in many iterations, is that piles of wood chips make an excellent home for critters that also love to eat from your garden. I had little dogs that would chase the hell out of anything squirrel-sized, and so had no problems this way, but I have heard of the experiences of some fellow permies who had problems with critters eating their
root veggies from below, largely because they were adjacent to the new critter hugel-condo.
Another reason I think it possible I haven't had critter issues is method of construction. I made sure that I layered in composted manures, spent
coffee grounds, and mostly finished
compost heavily on any fresh wood, and sifted in mixed topsoil and mineral subsoil, such that there were no air pockets, and such that a serious amount of shifting and percolation of
water would have to happen for any voids to form.
I also peed around the perimeter of the bed regularly, and though I did this for added nitrogen, I believe it played into critters not wanting to visit my garden or set up shop.
For your needs, if you built the raised beds as you say and filled with wood chips, I would pack them in solidly. Water will carry soil through the wood chip pack gradually, and I think it preferable to minimise soil loss, but it
should also regularly fill in any possible animal habitation.
In your position, I would also
pee around the beds, directly into the wood chips. It will speed wood chip decomposition and you will need to add more over time, but it might also deter anything with a shred of predator wariness that might otherwise chow down on the candy buffet that is your garden. That, and the faster the chips decompose, the more organic matter you'll have in your soil.
I would also suggest thinking about the use of coffee grounds mixed in or layered overtop of the wood chip wall and watered into it. Worms
love coffee grounds, and they are also rich in nitrogen.
If it seems like I am suggesting you accelerate decomposition of the wood chips, I am. The less structure the wood chip mass has, the easier it will be for it to fall in on itself, collapsing potential critter burrows.
Great idea, though. I can't wait to hear others chime in on this one. Keep us posted, and good luck!
-CK
A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, take orders, give orders, cooperate, act alone, solve equations, analyze a new problem, pitch manure, program a computer, cook a tasty meal, fight efficiently, die gallantly. Specialization is for insects.
-Robert A. Heinlein
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