Carbon sequestration in soil describes capturing and long-term storing atmospheric carbon dioxide or other forms of carbon in plants, soils, topography, and the ocean. It has been proposed to slow down the atmospheric and marine accumulation of greenhouse gases to mitigate or defer global warming and avoid all the irreversible effects of climate change.
Soil carbon sequestration, also called “carbon farming” or “regenerative agriculture,” includes various ways of managing land, primarily farmland, so that soils absorb and hold more carbon.
Increasing soil carbon is accomplished in multiple ways:
(1) reducing soil disturbance by opting for low-till or no-till practices or planting perennial crops;
(2) changing the planting schedules or rotations by planting cover crops or double crops instead of leaving fields fallow;
(3) managed grazing of livestock; and
(4) applying compost or crop residues to fields. In addition to providing local environmental and economic benefits, these practices can capture carbon dioxide (CO2) from the atmosphere and save it in the soil layer, making them a form of carbon removal.
Potential Scale and Costs
Soils hold three times the carbon currently in the atmosphere or almost four times the amount held in living matter. But over the past 10,000 years, agriculture and land conversion have reduced soil carbon globally by 840 billion metric tons of CO2, and many cultivated soil plots have lost 50–70% of their original organic carbon. Because soils have such a large storage capacity, enhancing soil storage by even a few percentage points makes a big difference.
A recent expert assessment estimates that soil carbon sequestration could be scaled up to sequester almost 2–5 CO2 per year by 2050, with a cumulative potential of 104–130 CO2 by the turn of the century at a cost of nearly $100 per ton of CO2 and sometimes even less than that. (Source: American University, Washington DC)
Carbon Sequestration Impact
Regardless of the carbon sequestration methods, all conducted activities are targeted at active carbon sinking, and atmospheric CO2 pollution could be reversed via this long-term removal process. However, it is worth highlighting that, due to the incentives and cost-effectiveness, biological carbon capture and sequestration have also gained the interest of several stakeholders in the agriculture industry.
One such example is the carbon farming initiative. This initiative assists farmers and landowners to earn carbon credits for storing carbon successfully or reducing greenhouse gas emissions. It emphasizes that the agricultural community can achieve environmental sustainability in the food supply chain. It is an example of a new green business model.
Soil has the potential to be a powerful carbon sequester vehicle, by mitigating and even helping to reverse global warming, as revealed in various soil tests for agriculture. The rising interest in different soil restoration initiatives could also be a crucial avenue to reducing carbon emissions and empowering long-term storage underground.
Carbon sequestration in soil
Carbon sequestration potential may be determined by understanding the historic SOC stocks under natural vegetation before conversion to other uses and the impacts of those land uses on the carbon loss. Land uses and management that trim down carbon inputs or increase losses than natural vegetation result in reductions in SOC eventually, creating a soil carbon deficit relative to the extent of carbon that previously existed in the soil.
This deficit represents a viable opportunity to store carbon from land use and management conversions when those changes result in increased inputs or decreased carbon losses. For example, reforestation on a former crop field can reduce the carbon deficit caused by years of agricultural production and sequester the carbon through higher root productivity than crops. Likewise, the creation of wetlands and ponds can sequester huge amounts of carbon because decomposition is significantly reduced in waterlogged soils from lack of oxygen; this can result in carbon gains that surpass the deficits resulting from past land use.
Other management practices like irrigation of pasture or rangelands, may also increase the carbon levels beyond historic Soil Organic Carbon stocks if carbon inputs under new management exceed levels under natural conditions. However, these changes in soil carbon typically take many decades, making actual measurements of changes in SOC stocks difficult.
How can farmers enhance soil carbon sequestration?
Farming already captures a considerable amount of carbon through cropland, hedgerows and semi-natural habitats, which often contain big plants like trees, which capture CO2 more effectively. Soil carbon sequestration can be further achieved by improving land management and altering land use to capture more carbon.
Here are some simple examples:
- Choose plant/crop species with more excellent roots which can deposit carbon in much deeper layers of soil, where it is secured from tillage and erosion.
- Adapting crop rotations. Shifting from an annual to a perennial crop increases carbon sequestration via plant root growth and decreases soil disturbance levels.
- Use cover crops during the fallow periods to provide year-round carbon sequestration and prevent rapid soil erosion.
- Reduce tillage to decrease soil exposure to air, and preventing the breakdown of soil organic carbon that releases CO2 back into the atmosphere. This can be attained through new technologies like precision seed planting.
- Livestock rotation. Rotating livestock prevents overgrazing and subsequent soil erosion through loss of plant cover.
- Increase the abundance of hedgerows and woodland.
With climate change being a pressing global threat, exploring all possible mechanisms to mitigate the atmospheric greenhouse gas buildup is imperative. Carbon affects the health of the soil layer, which can determine its fertility and profitability for the farmers.
Many factors affect soil carbon, like temperature, weather, soil acidity, and geography, among other things. However, management decisions on the farm play a significant role as well.
Managing soil health is all about finding the right balance between carbon input and output. Minimizing soil disturbance, covering the soil, and cultivating crops in rotation are ways soil can be managed that account for soil carbon and, ultimately, soil health.
Building soil carbon gains takes time; long-term commitment is essential for healthy soils. Added incentives in carbon farming can offer short-term gains while upholding a long-term outlook on the sustainability of farmland soil health. To know more about this, please contact SoilOptix® today! Or visit https://soiloptix.com/ for more details!