Fractionation is conducted to elucidate the fate of organic matter in the soil. This can have several purposes, such as understanding processes of soil organic carbon (SOC) stabilization, quantification of potentially labile SOC or short-term plant available macro-nutrients, quantification of environmental changes on long-term SOC sequestration or calibration and initialization of carbon turnover models. Based on specific research questions and views of SOC turnover and stabilization, a myriad of different fractionation schemes have been developed and performed during the last three decades. Fractionation of SOC is often aimed at separating the bulk SOC into fractions with varying turnover rates.
This website will introduce the most common physical, chemical and combined (physical+chemical) methods, provide detailed guidance on how they have to be performed in the lab and provide background information on the purpose of the fraction methods and their advantages and disadvantages. This website is related to the publication “Isolating organic carbon fractions with varying turnover rates in temperate agricultural soils – A comprehensive method comparison” (under review in Soil Biology and Biochemistry) in which 20 different fractionation methods were compared with regard to isolating fractions with distinct turnover rates.
The following methods were tested in the mentioned study, and are described in detail in the guidelines:
|Density Sollins2||5||Ultrasonic||1.6, 2, 2.4, 2.8|
|Particles+Density Six||4||HMP, glass beads||1.85||0>53>2000|
|Particles+Density Shaymukhametov||5||Glass beads||2||0>20>1000|
|Particles+Density Diochon||5||Glass beads||1.7||0>5>53>250>2000|
|Particles+Density Balesdent||5||Glass beads||1||0>50>200>2000|
|Chemical||Oxidation Mikutta||2||NaOCl, HA|
|Combined||Particles+Extraction Soong||5||Glass beads||K2SO4||0>63>2000|
|Aggregates+Particles+Density+ Extraction Kaiser||10||Ultrasonic||Na4P2O7||0>0.45>53>250|
|with method class and ID, number of fractions isolated, dispersion method (HMP=hexametaphosphate), applied density [g cm-³], chemicals used for oxidation / extraction / hydrolysis (Ox/Ex/Hyd, HA=Hydrofluoric acid), and size ranges of the isolated particles or aggregates [μm]|
The guidelines are open to grow. New methods, or methods that have not been applied within the SOMfractionation initiative can also be displayed. Please send an email to firstname.lastname@example.org if you want to suggest additional material to be published on this platform.