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Originally Posted by Michaelangelica
Quote:
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Originally Posted by malcolmf
Originally Posted by malcolmf
This is a key point in relation to your beasties, Michael. Models of the soil carbon cycle (e.g. Colorado Uni's Century) usually allow for such pools as fast (1 year), slow (decades) and stable (centuries / millennia) turnover rates. However, even these are approximations: some papers on mycorrhizae suggest their turnover time can be as little as five days, as compared to the glomalin they produce which seems to join the slow pool.
The headline is that, once creatures get hold of carbon, it is as good as gone, back to the air. This implies a trade-off between the two main goals of carbon burial, namely removal from the air and agricultural productivity. The former does not want creatures to access the carbon, the latter does. We have to examine our motivations for making terra preta, and the two camps might choose very different methods as a result. I suggest that atmospheric goals might require high-tech, high-volume, highly recalcitrant carbon while soil goals might require something much closer to Amazonian practices or RBlack's carbon-compost approach.
Your history is in compost, isn't it? How do you feel about the potential conflict of goals between atmosphere and soil?
M
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Well I've had a BIG THINK and it didn't help.
Does anyone know the answers to your questions?
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Sorry I missed this earlier:
I think I have a point that somewhat answers the question regarding respiration and the "atmospheric goals."
The respiration is indicative of growth and reproduction of the wee beasties in the microbiome.
While much of the carbon is respired for energy, a proportion is incorporated into the growing biomass.
It is the maintenance of a large healthy stable biomass that is the leveraged advantage of bio-char enhanced soils.
For instance, you could bury a pound of char in the desert and you'd have sequestered a pound of carbon.
....But if you add a pound of manure, three pounds of water, and a pound of inoculated char, to 10 lb. of desert dirt (total =15 lb.),
suddenly you'll have 20 lb of rich healthy soil.
[numbers and timeline may not be accurate 
]
...but for the purposes of illustration....
That (magically appearing) extra 5 lbs comes from the increase in living biomass within the soil.
That's 5 lbs of CO2 that is not floating around anymore, regardless of how much CO2 was cycled from the atmosphere to their food and back to the atmosphere--a proportion, equal to 5 lbs, was co-opted for growth and reproduction.
Feed this 20 lb of soil an extra pound of manure and you might get up to 25 lbs total (keeping moisture content at 3 lb). ....There's another 4 lb CO2 sequestered.
Now if you let the soil dry out or starve, then the 9 lb of biomass would die back and release most of their stored carbon.
...although given enough time as healthy soil, there would be a good bit of glomalin left behind.
Char does increase the soils resilience to starvation and drying, but there's limits to that of course.
Remember there are lots of algal species in the healthy soil biome also. Think of soil as an organism that breathes in CO2 during the day and exhales CO2 at night, while a small proportion of all that CO2 gets incorporated into its growing biomass.
The biomass isn't eating the char for food (much), but is eating SOM (CO2 from the atmosphere) or fertilizer (also CO2 from the atmosphere).
The same is true for nitrogen, nitrates, etc. although only about 1/5 the weight of biomass/ lb.CO2, if I recall correctly.
A lot of these experiments on amending soils with biochar, which report plumes of CO2 (or NOx's), are just snapshots of a bacterial bloom within the life of the biome, and/or the release of gas from the subsequent die-off of that bloom.
Results need to measure the long-term effects and stability, rather than the immediate reaction to the addition of something like char or fertilizer. Think about how fishtank chemistry fluctuates after a change in buffers, nutrients, or populations--soil would be similar.
This is also similar to the "iron fertilization of oceans" problem. They can "fertilize" and cause an algal bloom, sequestering CO2; but unless the bloom is stabilized or incorporated into the food chain, the CO2 will only be sequestered as long as the bloom lives.
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...and speaking of compost:
Even composting temperatures, moistures, and inoculants can be managed to minimize release of gases and maximize incorporation into biomass.
And remember, don't sweat the snapshots. Respiration is carbon neutral in the long run, but biomass is like gold (as long as we steward life everlasting).
~
p.s.
...hmmmm. Do all these blanket statements and overgeneralizations come together to paint a picture?
Does the focus on respiration now seem secondary to the long-term health of the microbiome?
~Thanks
