A new automated technique for measuring respiration in soil samples

An automated 36 place valve to provide continuous soil respiration measurements was constructed. The valve is fully computer controlled and can sample and purge the soil atmosphere as frequently as every 75 minutes. The concentrations, automatically measured by the valve, are essentially identical to those measured manually by gas chromatography in the concentration range of 0.1 to 1% CO₂, and are kept in this range by adjusting the mass of soil and the sampling frequency. Data are transferred automatically to a computer spreadsheet program for data handling and plotting on either a rate or cumulative basis. The system has proved reliable over many thousands of analyses and has made detailed analysis of microbial activity on a continuous basis possible.