The soil beneath our feet is a living entity. It is home to many microbes on Earth responsible for crucial processes such as decomposition and supporting plant health.
Boosting soil organic carbon in the world’s agricultural land by that much could increase carbon capture by croplands and grasslands by approximately one gigatonne per year over the next 30 years
While this is still a good practice, this is not as easy as people seem to think it is.
if we only increase our soil organic carbon by 1% globally, we can solve climate change!
even a fraction of a percentage change in SOC is a big deal.
1% = 10,000 ppm = 10,000 mg/kg of soil.
Generally, when we consider soil fertility calculations, we refer to what is called a hectare furrow slice (HFS). It’s a 1 hectare (ha) area, 20 cm deep (20 cm is pretty reasonable for average topsoil depths).
The average bulk density of soil is ~ 1.2 Mg/m3… you see where this is headed. Math, that’s where (fml… I signed up for soils because I hated math…).
So, you 100 m x 100 m x 0.2 m HFS weighs 2,400 Mg.
2,400 Mg = 2,400,000 kg of soil/HFS
10,000 mgcarbon/kg of soil x 2,400,000 kg soil = 24,000 kg of carbon/HFS
Now, that’s assuming you’re adding pure carbon.
Assume 75% of your amendment is carbon; that means you’ve got to scale that number up by 25% to account for amendment purity. Oh, and we’re not even factoring loss into this yet…
So as you can see, even a slight change in SOC is a big deal. I used 1% because my brain is cooked, but my point remains, even if you change it by 0.1%, you’re still looking at adding 240 kg of pure carbon per hectare…globally. We’re going to need a lot of biomass.
Good article. Touches on all of the issues.
While this is still a good practice, this is not as easy as people seem to think it is.
if we only increase our soil organic carbon by 1% globally, we can solve climate change! even a fraction of a percentage change in SOC is a big deal.
1% = 10,000 ppm = 10,000 mg/kg of soil.
Generally, when we consider soil fertility calculations, we refer to what is called a hectare furrow slice (HFS). It’s a 1 hectare (ha) area, 20 cm deep (20 cm is pretty reasonable for average topsoil depths). The average bulk density of soil is ~ 1.2 Mg/m3… you see where this is headed. Math, that’s where (fml… I signed up for soils because I hated math…).
So, you 100 m x 100 m x 0.2 m HFS weighs 2,400 Mg.
2,400 Mg = 2,400,000 kg of soil/HFS
10,000 mgcarbon/kg of soil x 2,400,000 kg soil = 24,000 kg of carbon/HFS
Now, that’s assuming you’re adding pure carbon.
Assume 75% of your amendment is carbon; that means you’ve got to scale that number up by 25% to account for amendment purity. Oh, and we’re not even factoring loss into this yet…
So as you can see, even a slight change in SOC is a big deal. I used 1% because my brain is cooked, but my point remains, even if you change it by 0.1%, you’re still looking at adding 240 kg of pure carbon per hectare…globally. We’re going to need a lot of biomass.
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