Examination of four methods for measuring soil respiration

We compared the accuracy of four methods for measuring soil respiration: the open-flow infra-red gas analyzer method (OF-method); the closed chamber method (CC-method); the dynamic closed chamber method (DC-method); and the aIkali absorption method (AA-method), using artificial soil medium (vermiculite with glucose and mineral nutrients) inoculated with Trichoderma sp. as respiring microorganisms. The CO2 emission rates from the medium were measured by the four methods once a day for 10 days. We compared the estimated amounts of glucose respired by Trichoderma sp. (EGR, an integration of measured CO2 emission rates for 10 days) with the actual amounts of glucose respired (AGR, calculated from weight loss of the medium during the same period). In the AA-method, the EGR value was 1.3 times larger than the AGR value, while in the OF-, DC- and CC-methods EGR values were almost the same as the AGR (0.95, 0.95 and 0.94 times respectively). Higher CO2 emission rates obtained by the AA-method were attributed to low CO2 concentration (20-250 mu l l(-1)) in the chamber, because at such low CO2 levels the respiration rate of Trichoderma sp. was enhanced by 20-70%. These results indicate that the OF-, DC- and CC-methods are more suitable for soil respiration measurement than the conventional AA-method. (C) Elsevier Science B.V.