cmolckg

cmolckg is not a standard, widely accepted term in core scientific usage; it is typically encountered as a misspelling of the unit cmolc/kg, which stands for centimoles of charge per kilogram of soil. The correct notation cmolc/kg is used in soil chemistry to express cation exchange capacity (CEC) and the amount of exchangeable cations that a given kilogram of dry soil can hold.

Overview and purpose

Centimoles of charge per kilogram quantify the soil’s ability to retain and exchange positively charged ions such as calcium, magnesium, potassium, and ammonium. This property is a key indicator of soil fertility, buffering capacity, and nutrient availability. Soils with higher cmolc/kg values generally have greater capacity to supply bases to plants and to neutralize acidic inputs.

Measurement and interpretation

CEC is determined by replacing all exchangeable cations with a counterion (commonly ammonium) and then measuring the amount of charge displaced, expressed in cmolc/kg. Values can range widely: sandy, low-activity soils may be in the low single digits, while clay- and organic-rich soils can exceed a few dozen cmolc/kg and, in some cases, approach or surpass 50 cmolc/kg. Base saturation, calculated as the proportion of CEC occupied by base cations (Ca, Mg, K, Na), is often reported alongside CEC to indicate fertility status.

Notes

If you encounter cmolckg in datasets or literature, it is usually a typographical variant of cmolc/kg. The underlying concept remains the same: a per-kilogram measure of soil cation-exchange capacity.

See also: cation exchange capacity, soil fertility, soil chemistry, base saturation.