Developing Chamber Measurement Protocols for Accessing Greenhouse Gas Emissions.

Management of agricultural soils can significantly impact the emission of greenhouse gases, especially nitrous oxide.  Chamber methods are widely accepted as an affordable means to access management impacts within plot-scale experiments.  However, careful planning is needed to design a sampling protocol that is appropriate for a specific study.  A range of approaches have been published, but the USDA-ARS GraceNet and the Global Research Alliance protocols have provided the most comprehensive guidance. Criteria for development of trace gas emissions protocol will be discussed. Selection of chamber dimensions should reflect crop spacing and height, with chamber height also coordinated length of chamber deployment time.  Sampling frequency will depend on the objectives of the study (i.e. estimation of annual gas flux verses response to N application or heavy rainfall).