I'm building a bunch of hugelkultur beds from the blowdowns, branches, trimmings, and sticks we have scattered around the property. This weekend I built a 20' long, 5' wide, 2-3' high pile of (mostly old / half rotted) wood of various sizes (0.5" - 8" dia). It's a mix of species: pine, hemlock, maple, beech, birch (possibly small amounts of others). Other beds will be roughly the same dimensions and wood mix. This bed is not (and none of the others will be) trenched -- digging in this location is too much work because of rocky soil and/or ledge outcroppings. This bed is on a slope -- perhaps 5-8% -- some of the others will be steeper and a couple will be nearly flat. It's built across the slope, but not perfectly on contour so that water can flow (slowly) around it and downhill beds can get some water.
A selection of these plants will end up in these beds.
I plan to cover the beds with composted horse manure and soil. (Probably more the latter than the former, since horse manure is easier to come by than soil.)
The compost is mostly horse manure with wood-based bedding. The soil is loamy/silty with gravel mixed in. I won't have time/resources to screen the quantity of soil required, so all but the largest rocks will end up in the beds.
- How deep does the soil/compost layer need to be?
- Is there a mix/ratio of soil to compost that I should aim for?
- Is it better to layer soil and compost or to blend them? (If layering, in which order?)