Is it possible to measure CO2 effluxes in an arable ecosystem using chambers without soil frames?

The push-in chamber and chambers with alternative gaskets were tested under fi eld conditions in order to estimate the rates of under- or overestimation of the CO2 effl uxes measured with chambers placed directly on a soil surface (without collars). Th e experiment was conducted on a spring barley fi eld which was harvested just before the measuring campaign. Th e following were tested: 1) a pushed-in chamber with a sharp metal blade installed on the edge of the chamber walls which was inserted to a depth of 1–2 cm to the soil, 2) a chamber with a 10 cm wide and 3 cm high rubber gasket, and 3) a chamber with a 10 cm wide and 2 cm high neoprene gasket. Th e results indicated that the application of the pushed-in chamber led to overestimation of the fl uxes by 55%, while application of chambers with alternative gaskets led to underestimation of the fl uxes by 30–40% due to the leakage of the gas from the chamber headspace through holes beneath the gaskets. Our experiment confi rmed that soil frames should be applied in fi eld conditions to assure the tightness of the chambers. Other tested solutions increase the biases of the chamber measurements and increase the uncertainties of the estimated CO2 effl uxes