Characterization And Classification Of Gleysoils On The Floodplain Of The Solimoes River (Iranduba And Manacapuru), Amazonas, Brazil

The floodplains of the Solimoes River are areas periodically flooded with predominance of Gleisols, where have lived a large number of small farmers of the region. The purpose of this study was to characterize and classify five profiles of Gleysoils distributed in three floodplain areas of the Middle Amazon basin, located in the municipalities of Manacapuru and Iranduba. After the morphological description, the soil horizons were sampled to perform physical, chemical and mineralogical analyses. Similarly, significant gleization was observed in all profiles of the soil matrix, with gray to gray-green color in the surface, and light to dark gray in the subsurface horizons, denoting iron reduction. The highest levels of the sand fraction in the subsurface horizons indicated the presence of different layers of fluvial deposition, while the high silt contents evidenced the nature of recent sediments and the low degree of pedogenetic development of these soils. The predominant soil cations were Ca2+ and Mg2+, with a percentage of exchangeable sodium (ESP), varying from 0.70 to 2.09. The organic carbon contents were lower than 80 g kg(-1), indicating recently deposited mineral sediments. The mineralogical composition of the clay fraction showed a significant presence of 2:1 clay minerals, but little variability among profiles. These results are reflected in high sum of bases and base saturation, characterizing eutrophic soils with high clay activity.