May 12, 2015

Soil Micro-Aggregate Bond Energies and Modelling Fragmentation

Rachel Efrat – British Geological Survey


  • Barry Rawlins
  • John Quinton
  • Andy Whitmore
  • Chris Watts


Micro-aggregates, clusters of soil particles less than 250 microns, are the elementary building blocks from which soil structure is composed. They provide an important indicator of soil quality and strength by determining key soil functions, such as porosity and gaseous exchange. They determine soil properties important in agriculture and are also responsible for the long-term sequestration (capture) of carbon in soils. This research will develop two techniques to further our fundamental understanding of aggregation processes to improve modelling of soil fragmentation. Although this research studies soil properties at a micro-scale, the impacts are broad, from applications in soil management and agricultural productivity, to improving our limited understanding of soils role in the carbon cycle.


Two novel techniques are being developed: the first method involves creating micro-aggregates artificially in a lab using a series of soil components in various ratios and combinations. The second technique will quantify and compare the stability of these aggregates by specifically measuring their bond energies with a combination of calorimetry (heat release), sonication (ultrasound energy) and a laser granulometer to monitor particle size distribution. This will improve the method and accuracy of standard aggregate stability tests widely used in soil science.

Why This Subject Matters to Them

“Global warming and climate change are at the forefront of government policy and development. Society is becoming increasingly concerned with protecting our planet and its resources for future generations. However, I believe soil generally remains unappreciated as the invaluable resource it represents. Soil is the food for our food. Not only do we depend on soil to grow food directly from, our livestock rely on it for food. It also presents a fertile medium to produce alternative energy resources (biofuels). It is essential we continue to research and attempt to document soil processes, functions, and properties, from the micro to field scale, to ensure we wholly understand and can sustainably manage this precious, highly biodiverse resource.”