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Old 11-07-2019, 12:00 PM
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Trapping carbon and returning nitrogen to the soil


I wonder if there is a composting method available that could return nitrogen to the soil while trapping the carbon without composting it? I see a lot on the hemp industry right now and how they are using it to make wood products. But I would also imagine it depletes the soil of nitrogen. It seems like hemp might be a useful plant for trapping carbon if it could be grown continuously without adding much fertilizer.
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Old 11-07-2019, 02:04 PM
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I'd think your best bet would be to rotate between hemp and some sort of plant that fixes nitrogen, such as clover, legumes, etc... Grow the hemp and do whatever you want with it, then grow the other plant, except at the end of that season, till it in to act as natural fertilizer for the next hemp crop. No additional nitrogen needed.

However, you'd still have to keep your eye on the potassium and phosphorus levels, as well as the micronutrients like iron, magnesium, sulfur, etc...
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Old 11-07-2019, 03:49 PM
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Originally Posted by HoneyBadgerDC View Post
I wonder if there is a composting method available that could return nitrogen to the soil while trapping the carbon without composting it?
It's not clear to me whether you think that composting doesn't return the carbon to the soil. Properly done, applying compost does return carbon, and presuming organic matter is increasing over time due to its use, does sequester it. Are you trying to come up with a way to remove the carbon in order to do something else with it?
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Old 11-07-2019, 05:09 PM
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It's not clear to me whether you think that composting doesn't return the carbon to the soil. Properly done, applying compost does return carbon, and presuming organic matter is increasing over time due to its use, does sequester it. Are you trying to come up with a way to remove the carbon in order to do something else with it?
I was under the impression that the carbon was eaten up by bacteria and released as c02 back into the air. I knew some of it stayed in the soil.
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Old 11-08-2019, 10:31 AM
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A good method of returning carbon and nutrients to the soil is adding fall leaves to your lawn and garden. I routinely mow over leaves in the fall to shred them and help them incorporate into the lawn, and use some shredded leaves for mulching perennials and fruiting plants.

Composted leaves eventually turn into leaf mold, which also is excellent for improving soil quality.
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Old 11-08-2019, 10:44 AM
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Composting is not a good long-term method for fixing carbon to the Earth. Maybe some small percentage stays, but the bulk will return to the air in the form of CO2 over the long term.
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Old 11-08-2019, 12:19 PM
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Composting is not a good long-term method for fixing carbon to the Earth.
Composting leaves beats hell out of burning them or dumping them in the landfill.
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Old 11-09-2019, 08:26 AM
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Composting leaves beats hell out of burning them or dumping them in the landfill.
Composting leaves and burning leaves have essentially the same effect, in the long run. The carbon is oxidized to CO2, either by direct burning or by the biological action of slime molds and other organisms. Sure, the composted leaves return minerals to the soil, but those minerals exist in the ashes of the burned leaves, they are not destroyed by burning.

Dumping them in the landfill has the potential of sequestering the carbon for much longer periods if the landfill is designed to keep the contents relatively dry so decomposition does not occur as quickly.
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Old 11-09-2019, 09:05 AM
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Dumping them in the landfill has the potential of sequestering the carbon for much longer periods if the landfill is designed to keep the contents relatively dry so decomposition does not occur as quickly.
While true, you must also take into account the fossil fuels that are burned in transporting the leaves to the landfill.
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Old 11-09-2019, 11:41 AM
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It seems to me that if we used fast growing plants to suck the c02 from the air that it would rapidly deplete the nitrogen in the soil so turn out to be a not very long term solution. If we had plants such as legumes that took nitrogen from the air then it might be more practical.
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Old 11-09-2019, 11:50 AM
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Is the assumption that all the carbon that was locked up in underground oil was once free carbon in the atmosphere correct?
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Old 11-09-2019, 11:50 AM
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Another factor in using shredded leaves in lawn and garden applications is that feeding the soil in this way lessens dependence on commercial fertilizers, which require large amounts of fossil fuels to produce and introduce plenty of CO2 into the atmosphere.

"The production of mineral and synthetic fertilizers, especially nitrogen using the Haber–Bosch Process, uses large amounts of fossil energy, mainly natural gas, releasing around 465 Tg carbon dioxide into the atmosphere each year (International Fertilizer Industry Association 2009)."

http://ncbi.nlm.nih.gov/pmc/articles/PMC2935130/

Shredded leaves are not an ideal fertilizer (partly because there's an initial depletion of nitrogen utilized by microbes to break the leaves down), but I like the idea of using less or no fertilizer plus the beneficial effect of leaf mold on soil composition.
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Old 11-09-2019, 12:40 PM
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Another factor in using shredded leaves in lawn and garden applications is that feeding the soil in this way lessens dependence on commercial fertilizers, which require large amounts of fossil fuels to produce and introduce plenty of CO2 into the atmosphere.

"The production of mineral and synthetic fertilizers, especially nitrogen using the Haber–Bosch Process, uses large amounts of fossil energy, mainly natural gas, releasing around 465 Tg carbon dioxide into the atmosphere each year (International Fertilizer Industry Association 2009)."

http://ncbi.nlm.nih.gov/pmc/articles/PMC2935130/

Shredded leaves are not an ideal fertilizer (partly because there's an initial depletion of nitrogen utilized by microbes to break the leaves down), but I like the idea of using less or no fertilizer plus the beneficial effect of leaf mold on soil composition.
Leaf mold is some powerful stuff, I have a large Chinese elm in my front yard that covers my lawn in small leaves. I switched to a mulching lawnmower and within a few months my entire lawn had turned to dichondra which I didn't even know I had.
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Old 11-09-2019, 12:48 PM
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Composting leaves and burning leaves have essentially the same effect, in the long run. The carbon is oxidized to CO2, either by direct burning or by the biological action of slime molds and other organisms. .
Hmmm, research needed. Pretty sure I've seen studies showing long term sequestration under at least some circumstances, but can't now remember just where. I may come back to this.

I will say rapidly that soils with a high organic matter percentage would be holding more C than soils with a low percentage, and that compost is a good way of raising soil organic matter. There may be however a limit depending on type of soil; so this might work better with depleted soils than with soils in good tilth to start with.

-- OK, here's a couple of cites, at least:

https://www.futurefarmers.com.au/you...on-in-the-soil

Quote:
Some of the practices that increase soil organic carbon include conservation farming (reducing or eliminating tillage and retaining stubble from previous crops), improving crop management (e.g. through better rotation), maintaining and improving tree/forestry management, improving grazing management and adding organic materials such as composts and manures.
http://nmsp.cals.cornell.edu/publica...actsheet91.pdf

Quote:
Adding organic amendments such as manure or compost can directly increase soil carbon, and also result in increased soil aggregate stability.
Those links are both to general information sheets for farmers; if anybody wants the studies they're relying on, that might take me a while longer to locate.
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Old 11-09-2019, 03:13 PM
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Originally Posted by thorny locust View Post
Hmmm, research needed. Pretty sure I've seen studies showing long term sequestration under at least some circumstances, but can't now remember just where. I may come back to this.

I will say rapidly that soils with a high organic matter percentage would be holding more C than soils with a low percentage, and that compost is a good way of raising soil organic matter. There may be however a limit depending on type of soil; so this might work better with depleted soils than with soils in good tilth to start with.

-- OK, here's a couple of cites, at least:

https://www.futurefarmers.com.au/you...on-in-the-soil



http://nmsp.cals.cornell.edu/publica...actsheet91.pdf



Those links are both to general information sheets for farmers; if anybody wants the studies they're relying on, that might take me a while longer to locate.
I think those methods slow down the release of carbon but eventually it will degrade back into C02. Oil reserves permanently captured the carbon until we decided to release it.
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Old 11-10-2019, 10:21 AM
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I think those methods slow down the release of carbon but eventually it will degrade back into C02. Oil reserves permanently captured the carbon until we decided to release it.
Once soils reach the organic matter level that's maximum for that particular soil, yes, carbon levels above that will return to the carbon cycle. But there are very large areas of soil that have degraded far below the level of organic matter they can hold. Raising all that soil, or significant quantities of it, back to its proper organic matter levels will increase for the long run the amount of carbon held in the soil to a great deal over the amount that's held there now.

If crop is being routinely taken from the field and shipped off elsewhere, this will require continuing effort by the farmers to keep the organic matter levels in those fields high. There are, however, significant additional benefits to the farmers who do so -- soils with high organic matter handle both drought and excess rain better, allow better root penetration and easier planting, and to the extent that tillage is necessary make tillage easier.

It's not the only thing we need to do, of course; nor is adding compost the only technique to use in order to accomplish it. But it's one of the things that needs doing; and applying compost is one of the ways to help accomplish it.
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