To Shake or Not to Shake: Novel Approach for Lab Microcosm’s Incubation Experiments to Estimate CH4 Oxidation in Paddy Soil
Submerged paddy soil is considered as a natural source of the greenhouse gas methane (CH4) because it provide the optimal condition (anaerobic condition) and hotspots for methanogens which lead to CH4.
Controlled microcosms incubation experiments (CH4 injection into the microcosms' headspace and subsequent shaking of soil as slurry) is commonly used to estimate CH4 oxidation in soil, but there is uncertainties associated with this methods because transition of CH4 from air to water is a limiting factor for the CH4.
To overcome the problem, scientists from the Institute of Subtropical Agriculture (ISA) of Chinese Academy of Sciences in cooperation with University of Gottingen, invented a novel approach for lab incubation studies by using silicone tube located in soil and compared with the conventional headspace CH4 injection.
Therefore they developed a microcosm with a silicone tube ( inner diameter: 4 mm, wall thickness: 1 mm, surface area: 18.8 cm2, volume: 1.2 ml) fixed around a plastic cap and tied with stainless steel wires form both ends, one of end connected with a needle as a sampling port.
Then they conducted an incubation experiment with/without soil silicone tube and with/without shaking in addition to test the location of CH4 injection-into the headspace (with/without tube) or into the soil (with tube) and the CH4 oxidation rate with time.
Scientists found that net CH4 oxidation rate reached the maximum values (1.6 μg C g-1 dry soil h-1) between the 3rd and 7th with novel approach method, which was 1.5–2.5 times faster than the respective CH4 oxidation after headspace injection without shaking.
However, shaking accelerated CH4 oxidation regardless of injection methods by 3.2–3.7 times (most intensively on days 3–7)
Furthermore, they found an overestimation of CH4 oxidation due to shaking because it increased the incorporation of 13C from CH4 into soil organic matter and microbial biomass by 1.8–2.7 times compared with novel approach the static control without tubes.
They concluded that conventional headspace CH4 injection can be substituted by novel approach for lab incubation studies.
The study entitled "To shake or not to shake: Silicone tube approach for incubation studies on CH4 oxidation in submerged soils" was published in Science of the Total Environment. Details can be found at https https://www.sciencedirect.com/science/article/pii/S0048969718349301.
The study was supported by the National Natural Science Foundation of China, Youth Innovation Team Project of ISA, CAS.
Contact: GE Tida
E-mail: gtd@isa.ac.cn
Institute of Subtropical Agriculture, Chinese Academy of Sciences
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