Qualitative mineralogy and chemical properties of a few soils from Sao Paulo, Brazil

Abstract

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.