Carbon dioxide fluxes following tillage from a mollisol in the Argentine Rolling Pampa

Carbon dioxide emission from soil plays an important role in the global carbon cycle. Short term losses of soil carbon due to tillage are of a variable magnitude. Our objective was to evaluate the effect of plowing the soil on CO2-C emissions during summer in a coarse-loamy mixed thermic Typic Hapludoll from the Argentine Rolling Pampa. Temperature after tillage was higher in the plowed soil than under no-tillage, being higher the soil water content in the later treatment. Plowing the soil did not produce an immediately im act on soil surface CO2-C emission, but induced an important CO2-C flush few days later. A difference of 16 up to 25 kg C ha(-1) d(-1) in the CO2-C emissions was observed from the second up to the fourth sampling dates after tillage. Difference in total CO2-C emissions between the plowed soil and the no-tillage treatment was 580 kg C ha(-1), during the 40 days measurement period. This difference in CO2-C emission was partitioned between residue decomposition and humus mineralization. Carbon mineralized from humus was 270 kg C ha(-1) higher under plow tillage than under no tillage. This figure represented an important extra loss of 0.48% of the soil organic carbon content from the 0-30 cm depth, as consequence of plowing in the warmest season of the year. (C) 2001 Editions scientifiques et medicales Elsevier SAS.