An automated chamber system for measuring soil respiration

To quantify the net effect of agricultural systems on CO2 emissions to the atmosphere, the amount of carbon fixed (primary production) and emitted (so il respiration) under different agronomic management must be estimated. A d ynamic chamber system was constructed to automatically measure CO2 concentr ation in chambers and provide diurnal flux estimates of soil respiration. I n fallow, the mean respiration was measured over 4 d using four chambers an d ranged from 6.5 to 8.6 g m(-2) d(-1). During this time, the coefficient o f variation between chambers ranged from 9 to 18%. The mean daily soil resp iration in fallow was also measured over a second period (13 d) using both chambers and a Bowen ratio technique. The mean value from the chambers was 6.4 g m(-2) d(-1), which was not significantly (P > 0.05) different from th at Bowen ratio value of 7.1 g m(-2) d(-1). The chambers were also utilized to measure the impact of tillage on soil respiration for 11 d following til lage. During this period, the tilled plot lost 92 kg ha(-1) of carbon compa red with 52 kg ha(-1) from the untilled plot. Approximately half of the tot al tilage-induced carbon loss from soil occurred in the first 48 h.