Chemical properties and mineralogy of soils with plinthite and petroplinthite in Iranduba (AM), Brazil

Revista Brasileira de Ciência do Solo

Cira Hortensia Pérez Garcia¹  Hedinaldo Narciso Lima²  Francisco Weliton Rocha Silva¹  Afrânio Ferreira Neves Junior¹  Wenceslau Geraldes Teixeira¹  Rodrigo Santana Macedo¹  Sérgio Guimarães Tavares¹ 

[1] ,UFAM Department of Soils and Engineering

关键词: Plinthosol;    soil fertility;    XRD;    weathering degree;    Central Amazon;    Plintossolo;    fertilidade do solo;    grau de intemperismo;    DRX;    Amazônia Central;   

DOI  :  10.1590/S0100-06832013000400011

来源: SciELO

【 摘 要 】

Large areas of Plinthosols with ferruginous materials such as plinthite and/or petroplinthite are fairly common in the Brazilian Amazon basin. This work was carried out to investigate the chemical behavior, mineralogical composition and weathering stage of four representative soil profiles with plinthite and petroplinthite, in Iranduba, AM (Central Amazon). Three well-drained soil profiles at high elevations were studied (P1, Plinthic Vetic Ferralsol; P2 and P3, Vetic Endopetric Plinthosol) and a contrasting poorly drained soil (P4 Haplic Plinthosol), located at low elevation. After profile descriptions, soil samples were collected from each horizon, air-dried, sieved (2 mm), and analyzed for particle-size distribution, pH, exchangeable cations (Al3+, Ca2+, Mg2+, K+, and Na+), as well as available P and total organic carbon (TOC) content. The minerals present in the clay and sand fractions, as well as in the ferruginous materials were identified by X-ray Diffraction (XRD). The weathering stage of these soils was assessed by means of Ki and Kr indexes, and the amounts of free and amorphous Fe and Al oxides by using dithionite citrate bicarbonate (DBC) and ammonium oxalate dissolution procedures, respectively. The results showed that all soils were extremely unfertile, with pH levels ranging between strong and moderate acidity, very low sum of bases and organic matter content, and of available P. The mineralogy of the soil profiles was very similar, mainly of the well-drained soils, with predominance of kaolinite and quartz in the clay and sand fractions, respectively. In the poorly-drained P4, 2:1 clay particles were also observed. These profiles can be considered highly developed according to the Ki index, however, the Ki value of P4 was higher, indicating that this soil was less developed than the others. In summary, these profiles with plinthite and petroplinthite can be characterized as highly developed and infertile soils and are, with exception of P4, well-drained.

【 授权许可】

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