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Updated: Mar 13, 2026

Aerobic Biodegradation Testing of Materials Using a Natural Marine Seawater Inoculum and Closed Loop Respirometer
Published on: October 24, 2025
Microbial respiration, but not biomass, responded linearly to increasing light fraction organic matter input:
Yichao Rui1, Daniel V Murphy1, Xiaoli Wang1,2
1Soil Biology and Molecular Ecology Group, School of Earth and Environment and Institute of Agriculture, The University of Western Australia, Crawley, WA 6009, Australia.
Abstract:
Rebuilding 'lost' soil carbon (C) is a priority in mitigating climate change and underpinning key soil functions that support ecosystem services. Microorganisms determine if fresh C input is converted into stable soil organic matter (SOM) or lost as CO2. Here we quantified if microbial biomass and respiration responded positively to addition of light fraction organic matter (LFOM, representing recent inputs of plant residue) in an infertile semi-arid agricultural soil. Field trial soil with different historical plant residue inputs [soil C content: control (tilled) = 9.6 t C ha-1 versus tilled + plant residue treatment (tilled + OM) = 18.0 t C ha-1] were incubated in the laboratory with a gradient of LFOM equivalent to 0 to 3.8 t C ha-1 (0 to 500% LFOM). Microbial biomass C significantly declined under increased rates of LFOM addition while microbial respiration increased linearly, leading to a decrease in the microbial C use efficiency. We hypothesise this was due to insufficient nutrients to form new microbial biomass as LFOM input increased the ratio of C to nitrogen, phosphorus and sulphur of soil. Increased CO2 efflux but constrained microbial growth in response to LFOM input demonstrated the difficulty for C storage in this environment.
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