Acoustic sensing and characterisation of soil organic matter

Dr Michal Kalkowski, UoS; Professor Tiina Roose, UoS
Rationale: 

How we exploit, treat, and manage soil is critical to the global carbon cycle and our resilience to global warming [1]. Lively soil ensures good crops and resistance to drought but is not easy to achieve [2]. For instance, adding organic matter to soil may, in the longer term, be counter-effective, increasing the CO2 emissions to the atmosphere. Recent research suggests that there is no 'one-fits-all' solution, and soil management should account for a broad spectrum of factors [2]. Effective soil management requires versatile measurement techniques for capturing soil condition in situ, preferably in a remote monitoring mode [3]. While some methods for determining soil organic matter exist, they are immature and either confined to laboratory settings or limited to large, regional scale. Acoustic sensing is a low-cost and versatile modality used extensively for monitoring and characterisation in various industries. This project aims to uncover how acoustic waves travel through complex soils with different forms and levels of organic matter and develop robust and field-applicable methods for measuring soil livelihood. Its outcome is pivotal for advancing soil management practices and learning their impact on the soil's health [3].

Methodology: 

While acoustic sensing is mature in various industry sectors, including geophysics, little is known about the effect of organic matter on wave propagation. Organic matter in soil can take numerous forms and originate either from natural processes or management practices. The project aims to explore several acoustic modalities to explore the effect of different forms of organic matter on wave propagation through the soil. These modalities include wave speed, scattering and attenuation for classical transmission/pitch-catch setups, and multi-sensor imaging based on array sensing. The project will measure the pre-selected signatures of interest in soil samples with controlled organic content over time (both by growing fine roots and adding organic matter) to look for trends promising for remote monitoring. Analytical and numerical modelling of wave propagation in complex media will underpin the experimental work by developing homogenisation techniques applicable to lively soil context and simulating the response with different material complexities. The project will deliver the first guidelines on using acoustic sensing in soil health management and combining it with other available or emerging methods.

 

Location: 
University of Southampton, Highfield Campus
Training: 

The INSPIRE DTP programme provides comprehensive personal and professional development training alongside extensive opportunities for students to expand their multi-disciplinary outlook through interactions with a wide network of academic, research and industrial/policy partners. The student will be registered at the University of Southampton and hosted at the Institute of Sound and Vibration Research. Specific training will

include:

  • Fundamentals of vibration
  • Finite element modelling
  • Signal processing
  • Vibration/acoustic measurement techniques
  • Lab training for preparing plant/soil samples

 

Eligibility & Funding Details: 

Please see https://inspire-dtp.ac.uk/how-apply for details.

 

Background Reading: 

[1] Govers, G.; Merckx, R.; van Oost, K.; van Wesemael, B. Soil Organic Carbon Management for Global Benefits: A Discussion Paper. In Proceedings of the Workshop organised by the Scientific and Technical Advisory Panel of the Global Environmental Facility‘Soil Organic Carbon Benefits: A Scoping Study’, Nairobi, Kenia, 10–12 September 2012

[2] Navarro-Pedreño, J.; Almendro-Candel, M.B.; Zorpas, A.A. The Increase of Soil Organic Matter Reduces Global Warming, Myth or Reality? Sci 2021, 3, 18. https://

doi.org/10.3390/sci3010018

[3] Sergei, C., Fu, S. Applications of physical methods in estimation of soil biota and soil organic matter. Soil Ecol. Lett. 2, 165–175 (2020). https://doi.org/10.1007/s42832-020-0038-2