Management systems resulted in rapid changes in some soil properties as soil respiration and bulk
density. Our results showed that the organic farming practices resulted in lower soil bulk densities and
higher soil microbial activity measured by soil respiration, and organic carbon. This was caused by the
higher inputs of organic matter an energetic substrate for the present microbial communities that were
activated to assure the turnover of applied nutrients.
Soil respiration evaluation in laboratory was based on the estimation of CO2-C evolution by an
incubation-alkaline absorption method [8]. The same points located for soil samples were used for
evaluation of soil respiration in field. The CO2-C was determined using an alkali absorption technique
[23]. The values were corrected to a 24 h basis and adjusted to equivalent at 60% WFPS through the
equation described by Parkin et al. [24]. The values in both soil respiration methods were expressed as
mg CO2 kg-1 soil day-1. Soil microbial biomass carbon (Cmic) was determined according to Vance et al.
[25] with extraction of organic carbon (C) from fumigated and unfumigated soils by 1 M K2SO4.
Organic C was measured using dichromate digestion and an extraction efficiency coefficient of 0.38 was
used to convert the difference in soluble C between the fumigated and the unfumigated soil in microbial