I try to make humus not compost. Compost isn't as stable as humus.
I have been pondering the fate of raw carbon lately.. what is the percentage of plant slash carbon that enters soil organic matter pools when:
As dead root in ground
As plant debris on surface
As compost on surface
As compost mixed in
A recent article I read described the increased efficiency of carbon conservation during decomposition through optimal C:N ratio. More carbon retained in the soil if C:N is at that magic 25:1 as the bacterial decomposers get the job done fast before volatilization can occur.
Another study suggested that in agroforestry systems surface slash results in less soil carbon than when incorporated.
Permie's seem to snub the compost maker out of reflex, preferring their surface litter. I always double dig, incorporating anything once living I can find when going from beaten earth to intensive production.
What say thee?
some areas have sifted compost on the top as well as a light mulch
Mt.goat wrote:I chose debri piles because Im highly suspicious of the caloric return of buirying woody debri.Have any pre industrial cutures done this sustainably?(sure Sep can take a forest and at great caloric expence get a lifetime of foood pruduction out of it but how productive will it be in 100yrs)I like to call my piles"the middens".
It sounds like these are deep enough that only a small proportion of the substance makes up the surface. I could easily imagine them transforming into well-mulched soil over the course of a couple years, depending on how they're built.
No one knows what process resulted in terra preta, but it has been suggested that worms played a major role in the incorporation of anthropogenic carbon into the soil ecosystem.
On a related note, I understand that a shallow lens of soil is often enough to establish plants on top of a slash pile.
Reading Steve Solomon, it seems like the challenge where I live will be to build fertility several feet down. Oakland has heavy clay soil and a Mediterranean climate, so I'll probably make it a priority when I get a longer-term garden, to build humus several feet deep, both as a moisture reserve for the driest part of the summer, and to offer nutrients when the top layers of soil have dried up and gone dormant.
One idea I had is to dig as deep as possible with a post hole auger (extending with pipe, if appropriate) and put in some fairly woody browns that will maintain ventilation all the way to the bottom (e.g. a bundle of sorghum stalks), plus a good mix of compostable materials. Ideally, the subsoil would absorb a fair amount of this organic matter over the wet season, and good access to air would both allow composting to happen, and help roots to survive deeper than they otherwise might. Gypsum has done amazing things for drainage in my current garden, so maybe some broken-up drywall in the bottom of the hole would help this setup not to drown early on. Ultimately, the idea is for the majority of deeply-buried carbon to be roots and other soil life that fled from dry conditions above, rather than the small amount that can fit in such a narrow hole.
It is posible to put a bit of soil on top and grow(and easily harvest) burdock and such.The biggest drawback to debri piles is slug habitat.They would work great in combo with ducks.