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Pesquisa Agropecuária Brasileira

Print version ISSN 0100-204XOn-line version ISSN 1678-3921


SOUZA, Rosinei Aparecida de et al. Quantitative and qualitative evaluations of soil microbes and biological nitrogen fixation in soybean. Pesq. agropec. bras. [online]. 2008, vol.43, n.1, pp.71-82. ISSN 0100-204X.

The objective oh this work was to define, for edaphoclimatic conditions of Brazil, acceptable levels of dispersion of some biological parameters, used in studies of environmental impact due to the adoption of new technologies with the soybean crop. Two experiments were performed in eleven counties, in six states and in the Federal District, with conventional and transgenic soybean. Evaluated parameters were: carbon and nitrogen of the microbial biomass, microbial respiration, microbial metabolic quotient, electrophoresis of soil DNA in denaturating gradient gel (DGGE), biological nitrogen fixation, number of rhizobial cells, nodule number and nodule dry weight, nodule occupancy by Bradyrhizobium strains, shoot dry weight, total nitrogen in shoot and nitrogen as ureides in shoot. The temporal variability for carbon and nitrogen of microbial biomass, microbial respiration and microbial metabolic quotient was adequate, and the maximum coefficient of variation was estimated at 35%. The homogeneity between replicates, treatments and harvests was confirmed by the DGGE method. In N-poor soils, the parameters of nodules and shoot dry weight, with maximum coefficient of variation 33 and 18%, respectively, were adequate for evaluation of biological nitrogen fixation, which contributed from 72 to 88% of total nitrogen in shoot.

Keywords : Bradyrhizobium; Glycine max; microbial biomass; DGGE; environmental monitoring; transgenics.

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