Evaluation of microbiological alterations in Allic Red-Yellow Latosol, under Eucalyptus sp. Monoculture in comparison with angico (Piptadenia sp.)

Abstract

Three groups of microorganisms were studied in cerrado soils (Red-Yellow Latosol), in order to check the probable alterations caused by eucalyptus monoculture. The quantified groups (bacteria, actinomyces and fungi), present in eucalyptus soils, were compared with those under Piptadenia sp. (angico) and under native cerrado vegetation. The largest microbial population found was that of the actinomyces, with fungi being the least frequent. Bacteria resistant to low levels of streptomycin (20 mg/ml) were encountered in greater numbers in eucalyptus soils, mixing with a high actinomyces population. In addition, under eucalyptus, the number of bacteria resistant to streptomycin was positively correlated with the Al³⁺ content of the soil. Under angico, there was a negative correlation of these bacteria with organic matter content. Soil under eucalyptus presented a lower organic matter content and a greater Al³⁺ saturation when compared with the soil under angico or even under cerrado vegetation. However, it should be stressed that clay contents were always greater in soil under angico.