Hi,
I'm new to this group, though it has already helped me to build my first ever hugelkultur and start on my second one here in southern Japan. I had to dig through 50 cms of compacted 'shirasu', crushed volcanic rock from pyroclastic flows, and 40 cms of compacted soil before reaching the natural sandy loam below. I'm kind of new to gardening so please excuse if I get terminology wrong. I built the bed up to a height of almost one and a half meters, putting all the contents back along with recycled lumber (untreated), clippings from my hedges, composted manure, fallen leaves, bark, dried out bamboo, partially composted weeds, old logs and branches and straw. I only need to go down 50 cms in my new bed before reaching sand and, though it still has a layer of shirasu, it is not as compacted as before. All that was growing here before was lichen, though other parts of the garting were covered in some sort of bindweed, goldenrod and many other nameless weeds. We've (my wife and I) had the property for just 4 months, so still much to do and much to learn.
I'm not sure if this is all going to work out, but I'm having a lot of fun trying. I can see that some seed have already germinated, probably mustard seed, and this gives me hope. We've already had a lot of rain since I finished the first bed a couple of weeks ago and I'm pleased to see that the bed has held together well.
Regards,
Dave