Nitrous Oxide and Carbon Dioxide Emissions from Aerobic and Anaerobic Incubations: Effect of Core Length
Guo, X.; Drury, C.F.; Reynolds, W. D.; Yang, X.; Fan, R.
Soil Science Society of America Journal 77(3): 817-829
ISSN/ISBN: 0361-5995 DOI: 10.2136/sssaj2012.0292
An important approach for elucidating soil respiration and denitrification processes includes laboratory incubation of uniformly repacked soil cores that are sealed at the base and maintained at constant temperature and water content; however, few studies have considered the impacts of core length on emission of the main respiration and denitrification gases, CO2 and N2O. Hence, aerobic and anaerobic incubation studies were conducted to evaluate the effect of core length (2.5, 5.0, 7.5, 10.0, and 15.0 cm) on CO2 and N2O emissions, using sieved (<= 4-mm) and uniformly repacked Brookston clay loam soil maintained at field capacity water content. The shortest core length (2.5 cm) appeared to enhance O-2 diffusion unrealistically, and as a result, N2O emissions under anaerobic conditions and CO2 emissions under aerobic conditions were probably overestimated. A boundary between aerobic and anaerobic respiration apparently occurred at the 8- to 10-cm length due to gravity redistribution of water within the core, and consequently, the 10.0- and 15.0-cm core lengths probably created artifacts by depressing CO2 emissions under aerobic conditions and by stimulating both denitrification and N2O reduction to N-2 under anaerobic conditions. Hence, core lengths of 5.0 to 7.5 cm may provide the most realistic CO2 and N2O emission results for repacked clay loam soils incubated at near field capacity water content. It was concluded that the most appropriate length for bottom-sealed incubation cores depends on soil type and water content and that unregulated core length can induce important artifacts into incubation estimates of CO2 and N2O emissions.