In a 19-year study, scientists dug roughly 6 feet down to compare soil carbon changes in different cropping systems. They found that compost is a key to storing carbon, a strategy for offsetting carbon dioxide emissions.
By moving beyond the surface level and literally digging deep, scientists at the University of California, Davis, found that compost is a key to storing carbon in semi-arid cropland soils, a strategy for offsetting CO2 emissions.
For their 19-year study, published in the journal Global Change Biology, scientists dug roughly 6 feet down to compare soil carbon changes in conventional, cover-cropped and compost-added plots of corn-tomato and wheat-fallow cropping systems. They found that:
- Conventional soils neither release nor store much carbon.
- Cover cropping conventional soils, while increasing carbon in the surface 12 inches, can actually lose significant amounts of carbon below that depth.
- When both compost and cover crops were added in the organic-certified system, soil carbon content increased 12.6 percent over the length of the study, or about 0.07 percent annually. That's more than the international "4 per 1000" initiative, which calls for an increase of 0.04 percent of soil carbon per year. It is also far more carbon stored than would be calculated if only the surface layer was measured.
Full details can be read here