ABSTRACT

A detailed soil survey of a forest pedosite at Michael Okpara University of Agriculture, Umudike, Abia State, Nigeria was carried out. The forest.pedosite covered an estimated area of 1.8 ha. Two soil mapping units (FOPED I and FOPED II) were delineated in the study area and five pedons was sunk. Three pedons (MFP1, MFP-2, MFP-3) were situated within the forest while two (CS-1 and CS-2) were situated at adjacent farmlands (as controls). The pedons were sampled and studied for their morphology, physical and chemical properties. Mapping unit FOPED I (represented by pedons MFP-1, MFP-2 and CS-1) covered 86 % (1.548 ha) of the forest area. They were generally shallow soils with < 50 cm depth. Soil texture ranged between loam (sandy clay loam and sandy loam) and sandy clay. The forest pedons (MFP-1 and MFP-2) retained more moisture with mean moisture content at saturation (32.1 % and 38.4 %), and AWC (11.2 % and 16.7 %) than the farmland pedon (CS-1) having 19.1 % (saturated MC) and 8.54 % (AWC). MFP-1 and MFP2 had lower mean bulk density of 1.54 g/cm3 and 1.56 g/cm3 respectively than CS-1 having 1.94 g/cm3. The soils ranged from very strongly acidic - moderately acidic with pH (H2O) range of 4.60 - 5.80. ECEC ranged between 7.95 - 12.7 cmol/kg (moderate to high) across the pedons. Higher mean organic matter content was recorded in the forest pedon (MFP-2) 3.99 % than MFP-1 and CS-1 having 1.64 % and 2.60 % respectively. Base saturation ranged from 74.6 - 92.1 % (high - very high) across all pedons. Mapping unit FOPED II represented by (pedons MFP-3 and CS-2) covered 14 % (0.252 ha) of the forest area. They were deep soils > 100 cm depth. Soil texture was generally loam (sandy clay loam and sandy loam) across both pedons. The forest pedon (MFP-3) retained more moisture with mean"moisture content at saturation (40.6 %) and AWC (18.6 %) than the farmland pedon (CS-2) having 23.0 % (saturated MC) and 10.4 % (AWC). MFP-3 had lower mean bulk density of 1.37 g/cm3 than CS-2 having 1.81 g/cm3. The soils were very extremely acidic - moderately acidic with pH (H?O) range of 4.30 - 5.70. ECEC ranged between 5.88 - 12.8 cmol/kg (moderate to high) across the pedons. Higher mean organic matter content was recorded in the forest pedon (MFP-3) 3.36 % than the control CS-2 having 2.28 %. Base saturation ranged from 65.7 - 96.3 % (high - very high) across both pedons. Pedons under mapping unit FOPED I were classified as Lithic Udorthents (USDA) and correlated with Eutric Loamic Regosols (WRB) while pedons under mapping unit FOPED II were classified as Typic Paleudalfs and correlated with Stagnic Loamic Luvisols. Under the Fertility Capability Classification (FCC), both mapping units were dominated with Loamy surface and subsurface horizon ‘L’ they were acidic soils ‘h’ and had limitations of ‘m’ (low organic carbon). Mapping unit FOPED I was classified as ‘LR'mh’ indicating high erosion risk due to shallow soils while mapping unit FOPED II was classified as ‘Lmh’.