soil organic carbon
a summarizing parameter including all of the carbon forms, from dissolved to total organic compounds in soils.  Soil organic carbon is a general term for the total of all the different non-living organic compounds in the soil (excluding dead plants and animals). The organic carbon in the soil is used by plants for nourishment as they grow, and the plants themselves replenish the resource when they decay after they die.
ISO. 2013. Draft international standard ISO/DIS 11074. 9 pp.
FAO (Food and Agriculture Organization of the United Nations); ITPS (Intergovernmental Technical Panel on Soils). 2015. Status of the World’s Soil Resources (SWSR) – Main Report. Rome, Italy: FAO. Available at http://www.fao.org/3/a-bc607e.pdf (accessed on May 26, 2017).