The Distribution of Silt, Clay and ExchangeableProperties of Aggregate Sizes of Four Soils

摘要

In this study the distribution of silt, clay and exchangeable properties of aggregate sizes of four soils were evaluated. The four soils studied were Entisol at Nsukka, Ultisol at Nsukka, Inceptisol at Eha-Amufu and Inceptisol at Ikem, all collected from four different sites in Nsukka area of southeastern, Nigeria. The land use types considered were fallow and cultivated. Soil samples collected from 0-25mm depth were air-dried at room temperature and were separated into five aggregate fractions 2.0-5.0mm, 1.0-2.0mm, 0.5-1.0mm, 0.25-0.5mm and < 0.25mm. Changes in the distribution of silt, clay and exchangeable properties of aggregate sizes of the four soils under wet and dried sieving of the four soils following cultivation were determined. The result of the study showed that Inceptisol had the highest silt, clay content in all the aggregate sizes among the four soils. The trend is Inceptisol > Entisol > Ultisol. Cultivation decreased the exchangeable bases, CEC and percent base saturation of those soils and their values were higher in the dry-sieved samples than wet-sieved ones. On the average acidity value of the dry-sieved samples were found to be higher than those of the wet-sieved samples. The variation in pH values of the aggregate fractions was found to be associated with the total exchangeable bases and percentage base saturation of the aggregates. Results obtained showed relative changes in the properties of dry and wet-sieving, even though their diameters are the same, implying that their loss during erosion will have differing effects on the soils.