Volume 2.2 Carbon
Soil carbon is probably the most important component in soils as it affects almost all soil properties. Soil laboratories are able to analyse different forms of carbon in soil.
Total carbon
Analysis and quantification of total soil carbon (TC) is necessary to estimate soil organic matter content, which is a useful parameter when evaluating the productivity of a natural system. Quantification of TC can be used to monitor soil carbon (C) stocks and to evaluate the role and effectiveness of C sequestration to mitigate climate change. Several methods are used to quantify TC.
The methods to quantify TC already harmonized by GLOSOLAN are the following:
Organic carbon
Carbon, as soil organic matter, alters the physical (e.g. structure), chemical (e.g. cation exchange capacity), and biological (e.g. microbial activity) properties of soils with impacts on plant growth and yield, biodiversity and the soil water retention capacity. The content of organic carbon of mineral horizons can be used also in soil classification, taking the textural class into account. However, the inferred organic carbon status of a soil should always be locally checked as it is only a rough estimate.
The methods to measure organic carbon are rather easy to run but a special effort should be made by soil analysis laboratories to provide the best possible quality data. This will allow monitoring of changes in SOC at both local and regional scales and also give a better idea of the future scenarios, not only for SOC content but also for atmospheric CO2 evolution. Did you know that the Global Soil Partnership launched a series of activities on soil organic carbon? For more information click here.
The methods to quantify SOC already harmonized by GLOSOLAN are the following:
Training video: Walkley and Black - titration and colorimetric method
Training video: Tyurin spectrophotometric method
Calcium carbonate
Calcium carbonate (CaCO3), dolomite [CaMg(CO3)2] and magnesian calcite [ Ca1-yMgyCO3] represent more than 90% of natural carbonates and play an important role in global carbon cycle. They are common especially in arid, semi-arid and sub humid soils where their amount and distribution influence the physical, chemical and biological properties of soils. For example; carbonates have a significant effect on soil pH, sorption-desorption, precipitation-dissolution and cementation reactions.
Soil carbonates are usually measured by dissolving carbonates in acid solution and then determination of either H+ consumption or Ca (and Mg) or CO2 production.
The methods to quantify the calcium carbonate content already harmonized by GLOSOLAN are the following: