SOIL AGGREGATION, STRUCTURAL STABILITY, AND ORGANIC CARBON CONSERVATION IN A DARK-RED LATOSOL UNDER DIFFERENT MANAGEMENT SYSTEMS IN THE BRAZILIAN CERRADO

Abstract

Management systems modify soil aggregation processes and directly influence organic matter conservation and structural stability in Oxisols. This study evaluated the influence of different management systems on soil aggregation, structural stability and organic carbon conservation in a Dark Red Oxisol under Brazilian Cerrado conditions. The evaluated systems were native Cerrado, Eucalyptus plantation, Pasture, No-Tillage, Heavy Disk Harrow and Disk Plow. Structural stability was determined by the wet sieving method proposed by Yoder, using mean weight diameter (MWD) and macroaggregate distribution as structural indicators. Organic carbon contents were determined using the Mebius method. Pasture presented the highest percentages of macroaggregates, whereas the highest MWD values were observed in native Cerrado. The highest organic carbon contents occurred in native Cerrado and No-Tillage. Correlations between MWD and macroaggregates ranged from 0.83 to 0.99, indicating a strong relationship between aggregation and structural stability. The absence of significant correlations between clay content and macroaggregates demonstrated that soil texture was not the main controlling factor of aggregation. The results indicate that structural stability depended more on organic matter and biological processes associated with management than on clay content. Organic carbon conservation resulted from the combined action of physical protection mechanisms provided by aggregates and organomineral protection mechanisms associated with the mineral fraction of the soil.