Healthy Soil, Organic Methods Transfer Carbon from Atmosphere to Soil

August 20, 2015 - Agricultural soils could absorb enough atmospheric carbon to reduce the threat of catastrophic climate change, but only if farmers and ranchers worldwide abandon damaging practices and work to restore soil health, researchers say.

A recent report by the Northeast Organic Farming Association of Massachusetts, (NOFA-MASS), citing dozens of scientific studies, calculates that global grasslands and croplands contain ample capacity to absorb and store enough carbon to drop atmospheric levels from the current 400 ppm to 350 ppm. In theory, that change could take place within five years - if farmers worldwide immediately altered their practices.

The NOFA-MASS report, “Soil Carbon Restoration: Can Biology do the Job?”, marks the launch of the group’s Soil Carbon Restoration Campaign, quantifying the potential of farming and land management practices to reverse atmospheric carbon buildup. The report explains the process by which soil microbes and plants team up to restore carbon to the soil, and the importance of biodiversity to the sequestration process.

While much atmospheric carbon is the result of the burning of fossil fuels, land clearing and cultivation for agriculture has released an estimated 136 gigatons of carbon into the air since the commencement of the industrial revolution, according to the report. (A gigaton is one billion metric tons).

The top three feet of global soil still hold an estimated 1500 gigatons of carbon, with more leaking into the atmosphere each year due to soil-degrading agricultural practices such as repeated tillage, use of chemical fertilizers and erosion, the report said.

However, numerous studies have shown that carbon can be quickly drawn from the air and returned to the soil with the use of cover crops, perennial plantings, crop rotations, crop diversity, integrated livestock management, and low- and no-till management. Many of these practices are commonly used in organic forming, the report noted.

Carbon is drawn into soils by the combined actions of plants and soil microbes, which also add structure to soil. Farming practices that feed the soil and protect soil microbes pull tons of carbon from the air, reversing the carbon leakage caused by soil-degrading farming methods.

Well-managed pastures have also been shown to draw impressive amounts of atmospheric carbon into the soil. One study, of land converted from row cropping to management-intensive grazing, documented the addition of 3.2 tons of carbon per acre, per year, to the soil.

Organic practice incorporates most of the soil-building strategies needed to fix carbon in the soil. However, the report notes that reducing tillage remains difficult for many organic farmers, who rely on it for weed control. The report calls for more research into low- and no-till systems, especially those using minimally-disruptive planting equipment and roller-crimper machines.

Read the report here, or by visiting the NOFA-MASS website at http://www.nofamass.org/.

By Maria Gaura, OFRF Communications

Image of testing for soil carbon levels courtesy USDA