About Carbon Sequestration:
- Carbon is found in all living organisms and is the major building block for life on Earth.
- Carbon exists in many forms, predominately as:
- Plant biomass, soil organic matter, and as the gas carbon dioxide (CO2) in the atmosphere and dissolved in seawater.
- Carbon sequestration is the long-term storage of carbon in oceans, soils, vegetation (especially forests), and geologic formations.
- Oceans store most of the Earth’s carbon.
- But the soils contain approximately 75% of the carbon pool on land.
- This is three times more than the amount stored in living plants and animals.
- Therefore, soils play a major role in maintaining a balanced global carbon cycle.
- Soils contain more carbon than is contained in vegetation and the atmosphere combined.
- Agricultural carbon sequestration has the potential to substantially mitigate global warming impacts.
- At the same time, employing methods to enhance carbon sequestration in soil will increase soil quality.
How is Carbon Sequestered in Soils?
- Through the process of photosynthesis, plants assimilate carbon and return some of it to the atmosphere through respiration.
- The carbon that remains as plant tissue is then consumed by animals or added to the soil as litter when plants die and decompose.
- The primary way in which the carbon is stored within soil is as soil organic matter (SOM).
- SOM is a complex mixture of carbon compounds, consisting of decomposing plant and animal tissue, microbes (protozoa, nematodes, fungi, and bacteria), and carbon associated with soil minerals.
- Carbon can remain stored in soils for millennia or be quickly released back into the atmosphere.
- Climatic conditions, natural vegetation, soil texture, and drainage all affect the amount and length of time carbon is stored.
Methods that significantly enhance carbon sequestration in soil include
- Conservation tillage (low till / no-till farming):
- It is the process of minimizing or eliminating manipulation of the soil for crop production.
- This includes the practice of mulch tillage, which leaves crop residues on the soil surface.
- These procedures generally reduce soil erosion, improve water use eﬀiciency, and increase carbon concentrations in the topsoil.
- Conservation tillage can also reduce the amount of fossil fuel consumed by farm operations
- Cover cropping:
- It is the use of crops such as clover and small grains for protection and soil improvement between periods of regular crop production.
- Cover crops improve carbon sequestration by enhancing soil structure, and adding organic matter to the soil.
- Crop rotation:
- The process of planting diﬀerent crops on a rotating pattern of years (e.g. corn-oats-clover).
- It will reduce the loss of carbon from the soil and with some additions (e.g. manure- lime-phosphorous) will add carbon to soils.
- All of the methods above are more widely used in organic farming than in conventional farming. Carbon stored in soils oxidizes rapidly.
Benefits of Soil Sequestration of Carbon:
- Removing CO2 from the atmosphere is only one significant benefit of enhanced carbon storage in soils.
- Improved soil and water quality,
- Decreased nutrient loss,
- Reduced soil erosion,
- Increased water conservation, and
- greater crop production may result from increasing the amount of carbon stored in agricultural soils.