cmolc

cmolc is a unit used in soil science to express cation exchange capacity (CEC) and related soil charge properties. It stands for centimoles of charge and is typically reported as cmolc(+)/kg of dry soil. The unit conveys the total amount of electrical charge that soil exchange sites (clays and organic matter) can hold and exchange with the soil solution.

In practical terms, 1 cmolc/kg equals 0.01 moles of charge per kilogram. This is equivalent to 10 milliequivalents of charge per kilogram, and also equivalent to 1 meq per 100 g of soil. Such relationships help connect cmolc with other common soil fertility units like meq/kg.

Common uses of cmolc include describing cation exchange capacity, base saturation, and exchangeable acidity. CEC values vary with soil texture, organic matter content, pH, and management practices, and are central to understanding nutrient availability and lime or fertilizer requirements. Although expressed in a charge-based framework, cmolc is often converted to other units for reporting and interpretation, depending on laboratory practices.

Measurement generally involves equilibrating a soil sample with a known salt solution to displace exchangeable cations, followed by quantifying the displaced ions. The resulting sum is reported as CEC in cmolc/kg. While the concept can be technical, cmolc provides a standardized way to compare the exchange capacity of different soils and to guide fertility management decisions.