Iron Oxide Properties as Support to Soil Morphological Features for Prediction of Moisture Regimes in Oxisols of Central Brazil |
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| Authors: | P E F da Motta N Kmpf |
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| Institution: | P. E. F. da Motta,N. Kämpf |
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| Abstract: | The relation between iron oxide properties and soil morphology was tested in a catena comprised by a sequence of Anionic Acrudox, Plinthic Acrudox, Plinthic Acraquox and Typic Acraquox soils, for prediction of drainage classes and moisture regimes, in the savanna region of Central Brazil. Morphological features, as mottles, nodules and low chromas of soil matrix, with iron content increasing in the sequence matrix → mottles → nodules, are evidence of iron segregation. The polygenetic nature of these soils is interpreted from the gibbsitic-kaolinitic mineralogical composition associated to high Al goethites attributed to a former dessilication weathering stage, and low Al goethites related to a presently wetter moisture regime. The soil morphological features, the iron distribution, and iron oxide properties are products of the selective dissolution of hematite inducing a xanthization process at the upper sites, followed by dissolution of “primary” high Al-goethite and formation of “secondary” low Al-goethite in mottles and nodules at the lower sites. Iron oxide properties are useful to distinguish preteric from present features in pedoenvironments, supporting the use of morphological soil properties to predict drainage classes and estimate soil moisture regimes in low intensity pedological surveys of these regions. |
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