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Mulch, compost and humus  RSS feed

 
Paul Cereghino
gardener
Posts: 856
Location: South Puget Sound, Salish Sea, Cascadia, North America
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puffergas wrote:
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?
 
        
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Trying to contact you.
 
Brenda Groth
pollinator
Posts: 4437
Location: North Central Michigan
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well as i was preparing my beds for my vegetable and orchard garden this spring..what i did was dug out the invasive grasses (quack and crab)...then forked the top layer of soil an raked it aside..i laid in to the depression any ammendments i could find, most of it was already partially rotted hardwood bark, as well as some compost and garden debris, then it was covered back over with the soil that had been raked aside and planted..when seeds begin to come up the entire area will receive mulch.

some areas have sifted compost on the top as well as a light mulch
 
Matt Ferrall
Posts: 555
Location: Western WA,usda zone 6/7,80inches of rain,250feet elevation
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It seems pretty site dependent to me.If I lived in the city,I would have more time than space and would want to use that extra time to maximize production per sq ft using/making compost,digging and growing annuals.With larger acreage such activities just dont seem to be the right scale(size)for the area you are trying to manage. It also seems soil type dependent.If I had clay soil,digging it would suck and nutrients/carbon seem less likely to go anywhere.My soil is a fine grey sand which leaches any organic matter away so charcol /slash and burn might be the best option(private property limits shifting cultivation though so the social structure reduces potential options like these).Carbon in my soil type is held mainly in living matter so I plant lots of trees to capture stuff as it rots.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".
 
Joel Hollingsworth
pollinator
Posts: 2103
Location: Oakland, CA
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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.
 
Matt Ferrall
Posts: 555
Location: Western WA,usda zone 6/7,80inches of rain,250feet elevation
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Do you think the caloric return for your efforts will be in the black? Today I tried my latest debri pile out.I made 8 piles 2`x2` evenly spaced in the garden area.I planted 4 comfry around each pile to smother the weeds that get thrown in.Then I refurbished that garden area and I didnt have to ever walk to dispose of a weed as there was always a pile within throwing distance.No digging,no walking,no hauling.weeding and fertilizing in situ.
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.
 
Paul Cereghino
gardener
Posts: 856
Location: South Puget Sound, Salish Sea, Cascadia, North America
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Interesting article - havn't dug through yet, but gist seems to be that Ca availability plays a role in formation of a stable soil carbon pool.

http://www.soils.wisc.edu/soils/courses/451/23.%20Oades%20Biogeochem%201988.pdf
 
                              
Posts: 63
Location: North West PA, USA
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My understanding is that an advantage of humus is its stickiness. It likes to stick to clay and fluff up the soil. I made a fuel that I call Fuelage and now I'm thinking it was made from humus. It did a good job of gluing it's self together as you can see in the photo at the bottom of the below link:

http://www.puffergas.com/fuelage/fuelage.html


Jeff
 
                              
Posts: 63
Location: North West PA, USA
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An interesting article comparing soil to a battery:

http://www.anlscape.com.au/files/soil_health/soil_-_the_battery_of_your_business.pdf


Jeff
 
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