Sampling guidelines and analytical optimization for direct greenhouse gas emissions from tropical rice and upland cropping systems

A meta-analysis of leading internationally/regionally recommended approaches to monitor agricultural GHG emissions is presented to put our sampling choices (e.g., chamber design, sampling intensity, sample storage and analytical corrections) into perspective.

Given our set-up, the sample retention capacity of polypropylene syringes and crimped glass vials with grey butyl-rubber septa was ∼6 hours and 10 days, respectively; and temperature correction of N 2 O and CH 4 concentrations was essential but plant volume correction did not affect the flux rates substantially. Optimization of gas flow rates, pre-column sample retention period, oxygen venting and temperature/current were found to reduce run time from >14 to 7 min per sample and enhance sensitivity by 30–40% while improving analytical precision from 15–30% to < 2% relative standard deviation (RSD).