AgreenSkills session, year: 1st session, 2016
Receiving laboratory: STEP group (Soil and Terrestrial Environmental Physics), ETHZ (Swiss Federal Institute of Technology), Zurich
Country of origin : France
Passive acoustic emission in soils: a new way to apprehend soil structure and monitor its dynamics?
Determining water and gas flows in soils, and thus physical and chemical environment for organisms, soil structure is essential for soil functioning. Appropriate soil structure management is needed for a sustainable agricultural production and environment protection. However, given its high variability in space and in time, partly due to climate and agricultural practice impacts, soil structure is still poorly defined and measured. New tools are used to describe soil structure in 3D), but they are still hard to access and too expensive to be commonly used. More in situ and quantitative methods are needed for this fragile element of soil. We thus propose the use of acoustic emissions (AE) to capture a new dimension of soil structure by passively listening to soil structural changes. Passive AE are produced in soils by various processes such as liquid bridge rupture, crack development, grain friction, etc. AE productions in soils are then due to particles movement; the hypothesis is that AE could be a useful tool to characterize the soil structure dynamics.
The aim is to develop AE-based metrics that would complement destructive sampling of soil aggregates and allow in situ assessment of soil structural status and dynamics under physical and biological processes of evolution. This would contribute to the development of a tool to easily and objectively determine soil structure in the field, and allow a better soil structure management in an agricultural context. Our results should also help understand soil structure dynamic and contribute to improve soil structure dynamics modelling.
Soil is a complex system, still unknown and too little considered by citizens, policymakers and land planners. I had my first experience in soil science research during my internship to obtain an Agricultural Engineer degree (Bordeaux Sciences Agro). I was then working on the digital soil parent material map of the French Brittany, and it confirmed my interest in soil science. In 2009, I decided to go further with a PhD (UMR SAS, INRA), during which I worked on soil evolution modelling at the landscape and century scales, at high resolution (2m), focusing on soil organic carbon dynamics and soil redistribution under water and tillage processes. In 2013, I pursued with a post-doc (US INFOSOL, INRA), working on the first high resolution (90m) 3D soil mapping for France, in the framework of the GlobalSoilMap project. In 2014, I was hired as a soil researcher (UR SOLS, INRA) to work on soil structure modeling from the plot to the field scale. Then, my work has always focused on the same subject, i.e. the soils. However, it has evolved as for the study scales and the considered properties. I am currently working on the potentiality of passive acoustic emissions (AE) by soils to characterize soil structure change; through a project I am leading. The first results are promising, and thanks to the AgreenSkills program, I have the opportunity to develop this very innovative topic by working with the STEP group (ETH, Zurich).
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* Lacoste, M., Michot, D., Viaud, V., Evrard, O., Walter, C. (2014). Combining 137Cs measurements and a spatially distributed erosion model to assess soil redistribution in a hedgerow landscape in northwestern France (1960–2010). Catena, 119, 78-89. DOI : 10.1016/j.catena.2014.03.004;
Lacoste, M., Minasny, B., McBratney, A. B., Michot, D., Viaud, V., Walter, C. (2014). High resolution 3D mapping of soil organic carbon in a heterogeneous agricultural landscape. Geoderma, 213, 296-311. DOI : 10.1016/j.geoderma.2013.07.002.