Soil as Carbon Storehouse: New Weapon in Climate Fight?

Post date: Apr 5, 2014 5:13:15 PM

Soils as carbon store house - to address climate change

The degradation of soils from unsustainable agriculture and other development has released billions of tons of carbon into the atmosphere. But new research shows how effective land restoration could play a major role in sequestering CO2 and slowing climate change.

The world’s cultivated soils have lost 50 to 70 percent of their original carbon stock – to the atmosphere, where it contributes to global warming.

What is soil carbon? Through photosynthesis, a plant draws carbon out of the air to form carbon compounds. What the plant doesn’t need for growth is exuded through the roots to feed soil organisms, whereby the carbon is humified, or rendered stable. Carbon is the main component of soil organic matter and helps give soil its water-retention capacity, its structure, and its fertility. Some of it can last thousands of years, in contrast to "active" soil carbon. When we have erosion, we lose soil, which carries with it organic carbon, into waterways. When soil is exposed, it oxidizes, essentially burning the soil carbon.

Top priorities should be restoration of degraded and eroded lands – we cannot feed people if soil is degraded - as well as avoiding deforestation and destruction of wetlands.

Storing carbon in soil; it is simple: it’s a matter of returning carbon where it belongs. There are so many options:

- We need better, regenerative agricultural practices can restore carbon in the soil while also boosting productivity and resilience to floods and drought; think of more permanent crops, cover crops, mulching (not burning), use of biochar, erosion control, better pasture management, and animal husbandry

- One promising strategy is adding beneficial microbes to stimulate the soil cycles where they have been interrupted by use of insecticides, herbicides, or fertilizers; plants with mycorrhizal connections can transfer up to 15 percent more carbon to soil than their non-mycorrhizal counterparts; to make this happen, the U.S. Department of Agriculture advises minimizing tillage and chemical inputs and using cover crops to keep living roots in the soil.

- As for agroforestry, greater species diversity matters.

- Making biochar (heating plant matter, manure, or other organic material in a zero- or low-oxygen environment) has potential to turn problem soils into productive soils while building soil carbon.

- Soil carbon is generally measured in the top 15 to 30 centimetres, whereas soil at depth may store carbon at much higher rates, for example, in land with deep-rooted grasses the soil can go down five meters or more: using deep-rooted perennial grasses can secure more carbon, and at a depth.

- Grasslands hold 20% of the world’s soil carbon stock. Much of this land is degraded.

Holistic Planned Grazing (HPG), where livestock are managed as a tool for large-scale land restoration, mimicks herding and grazing patterns of wild ruminants that coevolved with grassland ecosystems. Animals are moved so that no plants are overgrazed, and grazing stimulates biological activity in the soil. Their waste adds fertility, and as they move in a herd their trampling aerates soil, presses in seeds, and pushes down dead plant matter so it can be acted upon by soil microorganisms. All of this generates soil carbon, plant carbon, and water retention. HPG doesn’t require more land — in fact it generally supports greater animal density - so it can be applied wherever livestock are raised.

This news is related to the soon-to-be published book on this matter. Vetiver is discussed in one of its chapters. And currently more research is developed (by researchers from Ethiopia and South Africa) to further quantify the contribution of vetiver.