SPATIAL VARIABILITY OF MINERALOGICAL ATTRIBUTES OF AN OXISOL UNDER DIFFERENT RELIEF FORMS. II - CORRELATION BETWEEN MINERALOGY AND AGGREGATION

Kaolinite, gibbsite, goethite and hematite are the main clay fraction components in Brazilian Oxisols. The abundance of these mineral influence the physical-chemical properties of such soils, which is thought to depend on the relief This study aimed to characterize the spatial dependence of the crystallinity of kaolinite, gibbsite, goethite and hematite and aggregates of an Oxisol under sugar cane and to assess the spatial correlation between the attributes. In a grid with regular 10 m intervals 119 samples were collected from a depth of 0.2-0.4 m. in an area of 1 ha, where the relief variations were mapped. The mean geometric diameter and the percentage of aggregates in the classes > 2 and < 1 mm of the samples, and mineralogy of the clay fraction was characterized by X ray diffraction These results were analyzed statistically and geostatistically. Cross semivariograms were established to correlate stability and the different aggregate size classes with the crystallinity of soil clay minerals. It was observed that the goethites with lowest crystallinity are related to the largest mean geometric diameter and size of aggregate, and that the attributes studied and their relations depend on the relief forms.