The aim of this study was to evaluate, in the field, the soilrespiration and bulk density underconventional and organic farming plots. The evaluations were made in different plots established as conventional farming system and organic farming system with six, nine, twelve, fifteen, eighteen and twenty one months old. Plots were divided in four transects (subplots) and ineach subplot were evaluated soil respiration, bulk density and porosity. The soil respiration was significantly greater in organic farming system with fifteen, eighteen and twenty-one monthsold as compared with conventional farming. Soil bulk density decreased fifteen months afteradoption of organic system. Theresults showed that the adoption of practices in organic farming plots increases microbial activity and decreases soil bulk density over time.