More and more studies, including in Brazil, have suggested the use of microbial biomass carbon (MBC) as a bioindicator of soil quality. Most studies employ two methods: the pioneer of fumigation-incubation (FI), in which the MBC is estimated based on CO2 emission from fumigated and non-fumigated soil samples after 10 days of incubation and fumigation-extraction (FE), in which MBC is estimated based on C extraction from fumigated and non-fumigated soil samples after 12 h. However, in Brazil the correlation between both methods has been evaluated in three ecosystems only: in the Amazon, the Cerrado and three soils of the State of Rio de Janeiro. In this paper the methods FE and FI were compared in a typical Dark Red Oxisol in the North of Paraná State. The analyses were performed in a 12 year-field trial in Londrina with six treatments, including three soil managements (no-tillage, NT; conventional tillage with traditional ploughing and disking, CT; and NT using a field cultivator every three years, FC) and two crop management types (crop rotation, CR; or multiple cropping, MC) systems. Four soil samples (0-10 cm) were taken: after winter harvest (wheat in CR and lupin in MC), after summer ploughing (for CT and FC treatments), after summer sowing (soybean in CR and maize in MC) and in the summer crop flowering stage. In general the variability was low by both methods and the coefficient of variation was higher, the lower the MBC values. No differences between the FE and FI methods were detected when the four samplings at different stages as well as when all treatments were considered together. When all treatments were analyzed together, the correlation between FE and FI was positive and statistically significant. However, when each treatment was considered separately significance was observed for the treatments NT and CT in CR and MC, but not for FC. Results indicate that both methods may be used to evaluate MBC under similar conditions in Northern Paraná, however, they also indicate that more studies should be performed in Brazilian soils comparing both methods as a function of qualitative and quantitative changes in the organic matter contents as well as in the incorporation of crop residues.
organic matter; methodology; conventional tillage; no-tillage; crop rotation
