The stability of organo-mineral complexes is an important characteristic related to the soil chemistry and physics of tropical and subtropical soils. This study was aimed at identifing the variables related to the stability of organo-mineral complexes, evaluated by ultrasonic energy necessary to complete soil dispersion, of six soils from South and West-Center regions of Brazil with distint texture and mineralogy. The ultrasonic energy to complete soil dispersion varied from 239 a 2389J mL-1, and was positively related to the soil organic carbon concentrations (R²=0.799, P<0.05). The clay mineralogy had an important role to the stability of organo-mineral complexes, which were related to the content of low cristalinity iron oxides (R²=0.586, P<0.10), but did not had relationship with the total pedogenic iron oxides. The qualitative analysis of the clay mineralogy, by X-ray diffraction, evidenced that gibbsite and goethite are the main clay minerals related to the stability of organo-mineral complexes, reinforcing the importance of these minerals on the physical protection and coloidal stability of the soil organic matter in the tropical and subtropical soils.
ultrasonic energy; clay; organic matter; mineralogy
