Soil Carbon Dioxide Fluxes with Time and Depth in a Corn Field.

Soil CO2 efflux is an important component of the terrestrial carbon cycle that influences global climate. The amount of CO2 emitted from soil to atmosphere has significant effects on processes of the soil-atmosphere system. However, most of the work on soil CO2 has focused on the measurement at the inter-face of soil-atmosphere above ground. The objectives of this study are 1) to measure soil CO2 fluxes with time and depth in a soil profile of the soil surface and the soil subsurface, 2) to investigate the effects of row positions on soil CO2 fluxes. 3) to compare surface CO2 effluxes determined by the gradient and closed-chamber methods. Surface soil CO2 fluxes were measured directly with closed-chambers at the following locations within a corn field: bare soil area (BARE), within-row (ROW), between-rows with roots (BR), and between-rows without roots (BRNR), with two long-term chambers at each location.  Soil CO2 concentrations were measured at 0-, 20-, 50-, 100-, and 200-mm soil depths of BR and BRNR locations using solid-state sensors. Observed CO2 concentrations were used with estimated soil diffusion coefficient to calculate soil CO2 fluxes with time and depth. The surface and subsurface determination of CO2 fluxes enabled the determination of CO2 production with depth.