Soybean is the most important oilseed cultivated in the world and Brazil is the second major producer.
Expansion of soybean cultivation has direct and indirect impacts on natural habitats of high conservation
value, such as the Brazilian savannas (Cerrado). In addition to deforestation, land conversion includes the
use of fertilizers and pesticides and can lead to changes in the soil microbial communities. This study
evaluated the soil bacterial and fungal communities and the microbial biomass C in a native Cerrado and in
a similar no-tillage soybean monoculture area using PCR-DGGE and sequencing of bands. Compared to
the native area, microbial biomass C was lower in the soybean area and cluster analysis indicated that the
structure of soil microbial communities differed. 16S and 18S rDNA dendrograms analysis did not show
differences between row and inter-row samples, but microbial biomass C values were higher in inter-rows
during soybean fructification and harvest. The study pointed to different responses and alterations in
bacterial and fungal communities due to soil cover changes (fallow x growth period) and crop
development. These changes might be related to differences in the pattern of root exudates affecting the
soil microbial community. Among the bands chosen for sequencing there was a predominance of
actinobacteria, -proteobacteria and ascomycetous divisions. Even under no-tillage management methods,
the soil microbial community was affected due to changes in the soil cover and crop development, hence
warning of the impacts caused by changes in land use.
