How to determine the right amount of substrate (glucose) to induce priming. For example, add 50 ug C per g soil per day (based on soil weight) or 50 ug C per MBC per day (based on microbial biomass C)? Should the amount of substrate added be based on soil sample dry weight or soil microbial biomass C? If labeling the substrate with 13C, about 2% atom is enough for priming? Also, what is the appropriate length for the incubation/priming study? like 2 weeks, 60 days, several months?
Hi,
too many questions at once, but I can give some short hints: the amount of substrate should be based on microbial biomass C. The final amount to be added will depend on the aim of your research: if you are looking at real priming, than at least total added C should be more than biomass C to get increase. 2% of 13C enrichment could be not sufficient, but it depends on sensitivity of your analysers. Length of incubation depends on your aims, but for real priming 2 weeks is too short according to published data (see also review Blagodatskaya and Kuzyakov, 2008 in Biology and Fertility of Soils). Hope this helps,
Sergey
it depends on what kind of microorganisms you want to get. Several recent papers show that you do not get with the conventional substrate concentrations many of the taxa which only come up if you use, e.g., E. coli media diluted 1/1000 fold. Obviously, there are many so called oligotrophic taxa. Incubations should be definitely longer than 2 weeks more like 60 days or even longer
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