I plan to incubate 200 g of soil with different treatments for one month. I want to measure the gas flux of CO2, N2O and CH4 at time point of 0,7,15 and 30 days with static chamber method. A college told me the following method: at certain time point, take out 30 g of wet soil (water content was determined), incubate them into a glass jar (125 ml) and seal the jar with a lid (with a septa) for 16 h separately. After that, 10 ml of gas in the jar will be extracted by a syringe and injected into a vial for gas-GC analysis. The amount of gas released can be calculated as the concentration multiply (the space of jar minus the volume of soil). I do not whether this method could work because 16 h of incubation could result in anaerobic environment. Can anyone give me the answer?
There are a number of articles in Soil Biology and Biochemistry and Applied Soil Ecology that demonstrate replicable methods for quantification of soil respiration, if you can message me with exactly what you are trying to determine, I would be happy to suggest a couple. Generally, sealed vials are incubated for 12-24 hours in the articles that come to mind; can they go anaerobic? Yes, but that is necessary for methanogenesis (if you ignore influence of microsites, though that is another topic entirely). Anyhow, if you can measure oxygen (depending on your GC setup), that may be useful in your final analysis. Also, if you are concerned about anaerobic conditions but have soil and resources to run multiple time points (i.e. 6, 12, 18, 24 hours) on the same sample (but multiple jars to avoid vacuum in initial sample influencing soil respiration rates), you may find some interesting results!
There are a number of articles in Soil Biology and Biochemistry and Applied Soil Ecology that demonstrate replicable methods for quantification of soil respiration, if you can message me with exactly what you are trying to determine, I would be happy to suggest a couple. Generally, sealed vials are incubated for 12-24 hours in the articles that come to mind; can they go anaerobic? Yes, but that is necessary for methanogenesis (if you ignore influence of microsites, though that is another topic entirely). Anyhow, if you can measure oxygen (depending on your GC setup), that may be useful in your final analysis. Also, if you are concerned about anaerobic conditions but have soil and resources to run multiple time points (i.e. 6, 12, 18, 24 hours) on the same sample (but multiple jars to avoid vacuum in initial sample influencing soil respiration rates), you may find some interesting results!
Do you really need 16 hours incubation to determine fluxes? you should maybe do a range finder test to determine minimum time required to produce a measurable change in gas construction (as Ryan suggested you can measure O2 a the same time if needed and also follow precautions suggested by Ryan re vacuum issues). Certainly if there is N2O flux, concentrations will be measurable over much shorter period than 16 hrs. Also if you are looking at N2O and CH4 production, there may be an issue with collecting small aliquots from your bulk soil sample and what implications this may have for Oxygen flux into your smaller sample (with much bigger surface area to volume ration than your bulk). This also potentially affects target gas flux out of the sub-sample (ie not just flux from top surface). Also will you take a sample to the full depth of your bulk sample (conditions may vary through your bulk sample)?. It may be worth thinking about using small cores of soil (and keeping them in the core - then you only have flux through the surface. Anyway measuring the flux from a sub sample will need very careful thought if that indeed is the only way to go.
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