Characterization and classification of soils along a toposequence in Eziama Ikeduru, Imo State, South-Eastern Nigeria

Inherent physical, chemical and morphological properties of soils in a place greatly determine the agronomic activities carried out in the place. Soils with high ECEC, high base saturation, low bulk density, high organic matter content, high silt clay ratio, etc. show high soil fertility. The toposequence in Eziama, Ikeduru which was formed from coastal plain sand was delineated into three physiographic units, summit middle slope and valley bottom. One profile pit was studied in each of the units. The profile pits were described with the procedure as recommended by Food and Agricultural Organization and soil samples from identifiable horizons were subjected to laboratory analyses. Coefficient of variation was used to measure the variation amongst selected properties. Selected soil properties were also correlated to measure the relationship existing between these properties. The data obtained showed that the color varied from dusky red (2.5 YR 3/2) to red (2.5 YR 5/8) and generally became brighter down the profiles. The texture ranged from sandy clay loam at the B horizons to sandy loam at the A horizons. The silt clay ratio ranged from 0.039 to 0.549, showing that more advanced weathering has taken place in the soils of the studied area. Organic carbon ranged from 1.2 to 13.6 g/kg and generally decreased down the pits. Total nitrogen was generally low and ranged from 0.34 to 1.1 g/kg. The ECEC of the area was also low, indicative of effects of leaching which is predominant in soils formed on coastal plain sands. The percentage base saturation ranged from 23.3 to 66.98%. The pH ranged from 5.37 to 4.82 (strongly acidic to very strongly acidic). The C:N ratio ranged from 3.4 to 16.59. The fertility status of the soils was generally low due to the low Ca:Mg ratio, low K:Mg ratio, high C:N ratio, low pH., the soils belong to the soil order Ultisols. The soil at the summit was classified as Inceptic hapludult, that of the middle slope as Typic hapludult and that of the valley bottom as Arenic paleudult.