Stability of aggregates of some weathered soils in south-eastern Nigeria in relation to their geochemical properties

The stability of some highly weathered soils of the tropics is controlled by their organo-mineral substances. Highly weathered soils from 10 different locations were sampled from their A and B horizons to determine their aggregate stability. The objective of the study was to determine the aggregate stability of the soils and their relationships with geochemical constituents. The major geochemical elements of the soils are quartz and kaolinite, SiO₂, Al₂O₃ and Fe₂O₃, while the dithionite extractable Fe and Al was greater than their corresponding oxalate and pyrophosphate forms. The mean-weight diameter from dried aggregates (MWD_d) and their corresponding wet mean-weight diameter (MWD_w) were related significantly (r = 0.64*). The dithionite extracted Al and Fe or the crystalline forms of these elements were outstanding in the stability of the aggregates. However, this did not diminish the influence of SOC reduced to third order level in the stability of the soils. The influence of SOC in these soils, however, indirectly manifested on the role of Fe_p and Al_p in the aggregation of these soils. The crystalline Fe and Al sesquioxides were very prominent in the aggregation and stability of these soils.