ABSTRACT
Soil organic matter may be differentiated into humic and nonhumic components. Humic
components or humus are the highly transformed, dark brown to black materials that are
closely associated with the mineral fraction. Nonhumic material includes both particulate
matter (e.g., dead roots) and simple soluble components that are part of the soil solution.
Although the definition is straightforward, the consistent separation of humic and nonhumic
components is problematic. It is a challenge to develop experimental methods that consist-
ently and definitively separate humic and nonhumic fractions.
