World’s Soil Resources

Figure 14.7 Soil organic carbon change in Canada 201. Source: Clearwater et al., 2015.
14.5.2 | Soil organic carbon change
The soil organic carbon (SOC) change indicator used in the national Agri-Environmental Indicators
programme assesses how organic C levels are changing over time in Canadian agricultural soils. The indicator
is based on the method used for the Canadian National Inventory Report (Environment Canada, 2014). The
indicator uses the Century model (NREL, 2007) to predict the rate of change of organic C content in Canada’s
agricultural soils due to the effects of land management change since 1951. These include changes in tillage
and summer fallow frequency, and change between annual crops and perennial hay or pasture. It includes
land use changes such as clearing forests for agriculture or breaking native grass for cropland, but does not
include the loss of C from the above-ground forest biomass.
No changes in SOC were assumed if there were no indicated changes in land use or land management. The
SOC change indicator does not consider soil erosion.
The SOC change indicator results are presented (Figure 14.7) as the percentage of total cropland that falls
into each of five SOC change classes expressed in kilograms per ha per year (kg ha -1 yr -1 ). Negative values
represent a loss of SOC from the soil and positive values represent a gain of SOC.
Status of the World’s Soil Resources | Main Report Regional Assessment of Soil Changes
463
in North America