Soil Organic Matter Physical Fractionation Device

Automating Soil Separation by Density

At a Glance

Researchers at Colorado State University have developed a laboratory instrument able to perform soil organic matter (SOM) physical fractionation on several soil samples sequentially without stopping between samples. The instrument fully automates the process and only requires a user to load and unload samples. This instrument will significantly lower the cost and operator skill set requirement, while largely increasing throughput. The device will allow for larger scale adoption of soil analysis that is essential in fighting climate change across the globe.


The world’s soils are increasingly recognized as a key battleground in the fight against climate change, nutrient pollution, and other pressing global challenges. Soils have the capacity to store vast amounts of soil organic matter (SOM), which aids in the provision of multiple ecosystem services and is widely recognized as a viable component of a diversified strategy to address the UN sustainability goals. Managing SOM stocks to effectively address global challenges requires a deep understanding of SOM formation, persistence, and function, which in turn requires separating SOM into a light and a dense fraction (POM and MAOM), see Figure 1.

Current laboratory methods used to perform SOM physical fractionation (separating a soil sample into light and dense fractions) is very labor-intensive, manual process that requires highly trained personnel, see Figure 2. Even with the use of skilled personnel, the procedure has a very low throughput with an estimated rate of 20 samples per week. Because of the low throughput and high labor cost associated with this process, analytical test facilities are reluctant to offer SOM physical fractionation.


The automated SOM physical fractionation device is designed to perform all the functions of the manual method automatically and to process multiple samples continuously without user interaction. The device contains a chain of sample holders that are fed through the SOM light fraction extractor station one at a time. Different filter cups are used for each sample to allow samples to be stored separately and eliminate the user interaction between extractions, See Figure 3.

The device has a full control system and user interface. The control system uses a combination of sensors to progress the sample chain from one sample to the next and locate each sample accurately within the extractor station. The user interface allows laboratory personnel to adjust certain parameters of operation prior to starting a cycle such as number of samples, volume of rinse water used, etc.


  • Designed to perform every function of the manual SOM physical fraction method.
  • Can process up to 20 samples continuously in current configuration.
  • User interface allows lab personnel to adjust various parameters of operation.
  • More compact iterations with higher throughput are contemplated.


  • Automate process so different soil analyses can be performed on the products.
  • Soil Science Research Laboratories.
  • Federal laboratories.
  • Soil Testing Laboratories.
Last Updated: October 2023

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