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Biomass to Soil Ratio  RSS feed

 
William James
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Location: Northern Italy
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Does anyone have a vague idea of how much biomass would be needed to create, say, 1 meter of top soil.

Assuming you are doing this on ground that has already 6-10 cm of topsoil, how much would you need to make a meter of good, well-draining, crumbly plant-loving topsoil.

I did a few searches and came up with nothing. Perhaps it is too dependent on climate and soil conditions. I'm in heavy clay slightly acidic, so maybe the objective of 1 meter of crumbly loam is just a dream.

It's like I can see topsoil being made on my sites, but then it seems to evaporate into the ether at some point.

Thanks,
William
 
Cesum Pec
Posts: 8
Location: Florida
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Here's an article that may prove helpful: weight of soil

If you use the general estimate that the top 6.7 inches of good, loamy soil is 2M lbs, one acre inch weighs roughly 300,000 lbs. with roughly 39 inches in a meter, you would need 11,700,000 lbs of biomatter to create an acre meter of soil. I'llleave it to you to do the heavy lifting with a really big wheelbarrow, and to convert to metric since I don't know if Italians even think in acres.

All the above is subject to so many variables in the types of materials, water content, decay rates, etc, that it is probably meaningless except to show that it takes a HUGE amount of material.
 
William James
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Location: Northern Italy
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Thanks for the reply.
This lead me to think (or reconfirm)....more wood, more roots, more plants don't need crumbly garden soil (shrubs, trees).

Grass clippings and the like, no matter how much, is adding nearly nothing to the amount needed to actually create soil. They might be good for their short-term nutrient value and soil-shading, but they aren't building soil. I heard it was a 20% loss from biomass-->soil. So would that be 20 meters height of biomass for 1 meter of soil?

I'll have to run those calculations based on acres and see what I end up with. I get your point that the calculations are pretty meaningless, due to all the factors you cite.

But on a very limited scale you might want to get a very deep, 1 cubic yard/meter-ish mound of great soil to plant annuals into. My problem is also compation, being in heavy clay. Where topsoil is in contact with subsoil, there is huge amounts of compaction and loss of drainage capacity. On occasion I have separated them (via hugelculture or even baled straw) and so far I seem to be getting good results with that, the soil seems better in general, more well drained, etc.

Thanks again,
William
 
Chris Kott
Posts: 796
Location: Toronto, Ontario
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If money weren't an issue, or if you could find both of these things in quantity for cheap, I would layer compost on a large scale using ramial wood chips from urban tree services and cattle/horse manure. Or, for ease of application, work them in windrows, perhaps tarps over them, and make sure there are lots of red worms and Black Soldier Fly Larvae. It could be done. I would like to know what BSFL and vermiculture do to persistent herbicides, because I know that heavy metal counts go down after worms pass through, for the reason that getting that amount of manure from organic sources would be rough.

But to make my point clearly, if carbon breaking down is your main problem, many tree services companies where I live will deliver ramial wood chips for free if you ask for enough of them. It's a waste product for them.

Or you could build a biochar kiln and get woodchips (if you can, I don't know where you are), and make really high-quality ammendment that will build soil structure and not break down. If I don't know what the most biochar you would want to use in terms of a ratio with your topsoil would be, but you could directly increase the your volume of topsoil and its structure that way.

-CK
 
William James
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Location: Northern Italy
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I did some remedial math and I came up with about 1,000 Kg (~2,200 lb) of biomass to create a cubic meter (~1 yard) of topsoil. It's actually 1,313 kg, but I'm assuming the spot is going to include a few centimeters or inches of topsoil already. Hugely rough estimate here, but it does get you thinking. That's like 4 of our big round staw bales. But if you add wetter stuff I don't think that would be impossible for small spaces. Maybe a grass+straw+manure+woodchip mix to get a good C:N ratio and get good structure.

Then there's the timing factor, since I'm sure this stuff breaks down and becomes sub-soil pretty quickly.

Unfortunately Chris, people here either own a mini wood chipper or they when there's more they burn the ramial wood. It's too bad because this area has a good amount of black locust, so the coppicing is, in theory, a sustainable practice.

I thought of going around with a mobile wood-chipping truck and asking to chip and run when I saw the people burning, but never got around to it. Finding biomass that doesn't contain yucky stuff is a huge problem for me. That's why I'm looking in the long run to grow my own biomass, which hopefully will include trees.

Another solution is to just lay the damn logs and whatnot on the ground and let the fungus work on it. I already do that as a mulch substitute with any branches I can break down into 6-10 inch bits.

Ho hum,
William
 
2017 Permaculture Design Course at Wheaton Labs
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