Submitted to: Brazilian Soil Science Congress
Publication Type: Proceedings
Publication Acceptance Date: 6/30/1997
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: The physical structure of soils results from the complex interactions between soil mineralogy, chemistry, and microbiology. Minerals make up most of the mass of soil aggregates. Oxisols are dominated by minerals with variable surface charge, primarily kaolinite, goethite, hematite, and hydroxy-interlayered vermiculite or smectite. Thus, the structural stability of Oxisols is likely to be more sensitive to changes in pH and ionic strength than soils dominated by minerals with a net permanent charge. Mineral surfaces can be modified by sorbed organic and inorganic species and there is evidence that sorbed organic matter may make kaolinite and goethite in Oxisols negatively charged at all normal soil pH¿s. Aggregation by soil organic matter plays a major role in Alfisols and Mollisols, but may be less important in Oxisols where aggregation by iron oxide minerals is relatively more important. Mechanical disruption of Oxisol aggregates appears to release clay-sized minerals from the aggregate interiors which are more easily dispersed than the minerals on the outer surface of the aggregates. A full understanding of soil structure formation and alteration in Oxisols will require an approach with integrates the mineralogical, chemical, and biological aspects which lead to soil aggregation or dispersion.