Methodology for soil respirometric assays: Step by step and guidelines to measure fluxes of trace gases using microcosms

This methodology is proposed to measure the fluxes of trace gases among microcosms and the atmosphere. As microcosm respiration we include both aerobic and anaerobic respiration, which may results in CO(2), CH(4), NO, N(2)O, N(2), H(2)S and H(2) fluxes. Its applicability includes the assessment of products biodegradability and toxicity, the effect of treatments and products on greenhouse gases fluxes, and the mineralization of organic fertilizers. A step by step procedure; the complementary parameters and good practices that might be taken into account to perform a microcosm experiment; and the tools nowadays available that could be useful in this respirometric methodology are presented. We included a spreadsheet with calculus examples. Samples were taken at 1; 30; 60 and 90 min after closing the microcosms to determine the gases fluxes. The dilution effect was negligible, as we present. Besides CO(2), we have successfully quantified the fluxes of CH(4) and N(2)O from the microcosms in a broad range of concentrations. This method is useful in technical and scientific studies, for instances to test new products and improve the understanding of microbial processes, respectively. • Simple materials are required to set up the microcosm. • Examples of (pre) treatments are given regarding water availability, fertilizer doses, pH adjustment and nutrients amendments. • The method was suitable to directly measure multiple trace gases fluxes, either produced or consumed during microcosm respiration.