| Sumario: | Mineralogical analyses of clay, silt, and oat soils, and of total free iron oxides, provide some clues to the chemical properties of the staged São Paulo soils. The soy-yellow Podzolic soils, which contained some micaceous silicates in the clay and silt fractions, had more permanent negative charge and more exchangeable aluminum than the red-yellow Latosols and the red Latosols that did not contain micaceous minerals. The ratio of pH-dependent charge to permanent charge was highest in the red Latosols and lowest in the red-yellow Podzolics. The relative affinity of the soil for Ca in the Na-Ca exchange equilibrium was highest in the red Latosols and lowest in the red-yellow Podzolics. Phosphorus fixation was correlated with iron oxide content within the soil group, but the overall relationship for all soils did not show a significant correlation.
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