Approximately 35% of global greenhouse gases (GHGs) come from agriculture. Some argues that human can reverse global warming by sequestering several hundred billion tons of excess CO2 through regenerative, organic farming, ranching and land use. Increasing the soil’s organic content will not only fix carbon and reduce emissions, it will also improve the soil’s ability to retain water and nutrients and resist pests and droughts.
To explore the potential of farmlands acting as a carbon sink without yield losses, Jiang Gaoming, a professor at the Chinese Academy of Sciences’ Institute of Botany, conducted an experiment on a temperate eco-farm in eastern rural China. Crop residues were applied to cattle feed and the composted cattle manure was returned to cropland with a winter wheat and maize rotation. Crop yield and greenhouse gas (GHG) emissions were carefully calculated according to the Intergovernmental Panel on Climate Change (IPCC) Guidelines for National Greenhouse Gas Inventories 2006.
This study showed that replacing chemical fertilizer with organic manure significantly decreased the emission of GHGs. Yields of wheat and corn also increased as the soil fertility was improved by the application of cattle manure. Totally replacing chemical fertilizer with organic manure decreased GHG emissions, which reversed the agriculture ecosystem from a carbon source (+ 2.7 t CO2-eq. hm-2 yr-1) to a carbon sink (- 8.8 t CO2-eq. hm-2 yr-1).