Soil CO2 concentrations and their implications in conventional and no-tillage agricultural fields

Abstract

Soil CO2 concentrations to a depth of 50 cm depth were monitored with Vaisala CO2 probes from June 2004 to May 2005 in conventionally plowed and no-tillage agricultural plots and found to be generally higher in the former than the latter. Soil CO2 concentrations were also higher in summer and lower in winter, but were modulated by harvesting and the application of crop residues. Analysis of diurnal variations in soil CO2 concentrations, soil CO2 effluxes, and soil temperatures revealed distinct differences between plots. The relative amplitudes of the variation in CO2 concentrations peaked at a soil depth of 5 cm. Soil CO2 concentrations were higher when there was higher soil water content after precipitation, while soil CO2 effluxes were lower under the same circumstances. These two results relate to the lower diffusivity at higher soil water content, which restricts CO2 efflux, leading to higher soil CO2 concentrations. Calculations reveal that in the shallower soil layer (0-5 cm), CO2 production was greater in no-tillage plots, whereas in the deeper layer (15-25 cm), it was greater in conventional plots.