Flow‐Through Incubation System for Monitoring Aerobic Soil Nitric and Nitrous Oxide Emissions

Formation and escape of the gaseous products of aerobic soil N transformation processes such as nitrification are logically studied in the laboratory using an incubation system that neither interferes with the diffusive transport of gases within the soil nor allows accumulation and further reaction of gaseous intermediates after their escape through the soil surface. In addition to satisfying these criteria, our flow‐through incubation system provides for continuously monitoring soil emissions of nitric oxide, nitrous oxide, and carbon dioxide, while also permitting soil analysis as frequently as required to characterize changes in the pool sizes and transformation rates of precursors involved in the production of these gases. Treated soil is placed both in the bottom of each incubation jar and in the eight (maximum) sample vials contained therein. The former serves as a continuous, undisturbed source of the measured gases while the latter provides convenient, preweighed samples for periodic chemical or microbiological analysis. Other features of the incubation system include (i) provision for anaerobic and sterile treatments, and (ii) automated air analyses and data acquisition controlled by a programmable timer that provides the flexibility to quickly and easily tailor the system's sampling, analytical, and recording functions to meet the specific needs of each experiment. Because the yield and composition of gases produced during soil N transformation processes is sensitive to incubation conditions, we propose that important features of this system be adopted by other laboratories to facilitate the comparison of research results by eliminating differences due to methodology.