An Open-flow Chamber with a Multiple CO2-Gas Analyzing System for Continuous Measurement of Soil Respiration in a Greenhouse

An open-flow chamber equipped with a multiple CO2-gas analyzing system (MGA) was developed for the continuous measurement of the soil respiration rate in a greenhouse. Two fans attached to the chamber facilitate airflow through it. The air from the inlet and outlet of the chamber is sampled, and then, its CO2-gas concentration is analyzed by the MGA, which consists of an infrared gas analyzer, an air pump, a flow meter, and a programmable data logger. The rate of soil respiration is evaluated based on the difference in CO2 concentration between the inlet and outlet air, and on the air flow rate. The chambers were installed into the ridge and the furrow, and the characteristics of soil respiration were then analyzed. The hourly change in the soil respiration rate was almost constant, and it was higher in the ridge (3.2 μmol m−2 s−1) than in the furrow (0.5 μmol m−2 s−1), which can be attributed to the small amount of surface soil in the furrow. On the other hand, the soil respiration rate on a greenhouse scale was roughly estimated and compared with the rate of CO2 loss from the greenhouse to the ambient air. The rates were nearly equal when the CO2 concentration in the greenhouse was constant. These results suggest that the soil chamber with the MGA is a useful tool for the dynamic analysis of soil respiration in greenhouses.