Spatial and temporal variability of soil respiration in agricultural fields

Abstract

Chamber measurements of CO2 evolution were made on bare soil, and in maize (1988) and wheat (1989) crops in order to study the spatial and temporal variability of soil respiration (Rsoil). Semivariograms showed no definite structure of spatial auto-correlation on bare soil when measurements were made along transects. Spatial variability was shown to occur at a scale smaller than 15 cm. In a maize crop, Rsoil in the row was significantly higher than in the interrow when the soil surface was dry due to the contribution of plant roots. Under wet soil conditions, Rsoil in the interrow compacted by the tractor wheel was lower than on noncompacted soil and no significant difference was found between rows and interrows. This was due to the role of microbial activity which was dominant except in the compacted interrow where lower airfilled porosity caused lower Rsoil. The maximum Rsoil during the growing season coincided with the period of maximum growth of both crops. A post-rainfall Rsoil burst is also described. -from Authors