Abstract: Concentrations of CO₂ and H₂O are important indicators of farmland microclimate. When using CO₂ and H₂O analyzers to determine indicators in the field, the hose must be used to transfer the gas to the analyzer，but the material and length of the hose will affect the setting time and accuracy of the CO₂ and H₂O when they were determined. In this study, 8 hoses and 5 lengths were used to screen the best material and length for CO₂ and H₂O measurements. The results showed that the setting times of CO₂ in different material hoses were in 9.20−11.47s, and the setting times of H₂O were in 9.67−18.93s. The stability analysis of the setting time of CO₂ and H₂O using the AMMI model shows that in the CO₂ concentration stability, the fixed effect caused by the length was the largest, followed by the material, and the material and the length were mutually exclusive. The setting time of CO₂ concentration of the peristaltic pump tube in the material was the shortest; while in the setting time of H₂O concentration, there was a significant interaction effect between the material and the length, in which the fixed effect caused by the material was the largest, and the length in the second place, and the setting time of H₂O concentration of Polyvinyl chloride(PVC) pipe was the shortest. Different materials had different interactions with different lengths. Each material had its own special adaptability to different lengths. Therefore, in the test process, chose the material and length of the shortest setting time according to the required measurement indicators to ensure the accuracy and efficiency of the data.

Key words: CO₂ concentration, H₂O concentration, Setting time, Hose material, Hose length, Microclimate of field