Developing a flow through chamber system for automated measurements of soil N2O and CO2 emissions

Continuous flow through chamber systems are recognized for their superiority in obtaining high resolution seasonal greenhouse gas (GHG) emissions data. In the current study, we combine Li-Cor 8100A CO2 flux system with the infrared N2O analyzer (Teledyne API, San Diego, CA) and a laser spectroscopic analyzer (Los Gatos Research Inc, Mountain View, CA) to design a robust setup for reliable concurrent measurements of N2O and CO2 emissions from automatic chambers and to obtain flux gradient N2O data from agricultural land. Field testing revealed considerable interference of moisture and temperature with the infrared N2O analyzer data, which showed a negative drift of up to 0.5 ppm at increased humidity (R2 = 0.76). Addition of desiccant column on line in an attempt to improve infrared analyzer N2O readings due to removal of moisture affected the N2O and CO2 baselines, likely due to flow modulation by the Li-Cor 8100A air pump. High precision output from the laser spectroscopic analyzer and stability of its baseline at variable temperature and moisture were preferable for combined automatic chamber and flux tower measurements. The total N2O produced at the site fertilized with 100 kg N ha−1 was 1.8 ± 0.7 kg N2O-N ha−1, and the total CO2 emissions were 4350 ± 1173 kg CO2-C ha−1 during the measurement period in the fall and spring. The high frequency of sampling and low labor intensity of the N2O and CO2 measurement setup allows for comparison of GHG emissions from short term events and across seasons, and establishes the basis for better understanding of emissions sources in agricultural systems.