About a week after the respiration chambers are installed (pushed 15 cm into soil), the CO2 flush from the soil disturbance caused by the installation should have diminished. It is now possible to measure the amount of CO2 respired from a known surface area by trapping it into jars of 1M NaOH during 24 hours.

Pipette 20mL of NaOH solution into the glass jar, and place it on the tripod in the center of the selected cylinder. Immediately cover the cylinder with the plastic snug-fitting lid, and cover the entire setup with aluminum foil. Note time zero.

After 24-hour incubation, retrieve the jar, pipetting 20mL BaCl2 into it before covering with screw-on lid. Take the jars to the laboratory for titration, using the color indicator noted previously and the standard 1M HCl.

Note that control treatments are performed by incubating sealed jars of NaOH solution in the field.

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