Soil carbon: multiple functions benefiting societies and the environment

Soil organic matter (SOM)—and thus organic carbon which accounts for over 50% of its mass—has a key role in the overall behaviour of soils and the agroecosystems they support: soil physical qualities, stimulation of soil biological activity, water and nutrient storage and availability for plants and pollutant regulation. The soil organic carbon content is generally considered to be the prime soil quality indicator, with respect to its agricultural and environmental functions.

The organic carbon content is naturally low in dryland soils—less than 1% of the soil mass—whereas in temperate regions it is 1–2% in cultivated soils and 4–5% in grassland and forest soils. Loss of organic carbon or SOM inevitably results in soil quality degradation and alteration of the soil’s associated functions, creating a vicious circle whereby soil degradation prompts a reduction in agricultural productivity and an increase in food insecurity, malnutrition and famine, etc. Conversely, increasing the SOM directly enhances soil quality and fertility, thus contributing to agricultural resilience and sustainability and, in turn, food security of societies and carbon sequestration.