Abstract
Increased population density has led to a lot of pressure on the limited natural/land resources of south-eastern Nigeria. This includes the need for laterite, sand, kaolin, gravel and clay for buildings, backfills and road construction. This has led to extensive unmoderated excavation of these resources, particularly in Anambra state. The excavation has in turns, culminated in increased intensity of land degradation in the state, underscoring the need to characterize and evaluate the land use potentials of such sites to better understand the nature of the soils and the impacts of the attendant land use. Samples were collected from the different horizons of the profile to evaluate the physical, chemical and morphological properties of the soils. Coefficient of variation was used to measure the soil variability within the profile. Land capability class was determined, which informed the land use and management recommendations. The results show that the soil is very deep (>21.5m). The soil texture ranged from sandy clay loam to sandy. Infiltration rate and saturated hydraulic conductivity decreased by up to 300 to 560 % with excavation. The soils were strongly acidic; organic carbon and total nitrogen was low but highly variable; Al, H, Ca, Mg, K, Na, and phosphorus were moderately variable while pH, CEC and base saturation (BS) were the least variable. The land capability class was IIIes. Given the evidence of erosion and preponderance of erodible Nanka sands in the subsoil, the site should be reclaimed as soon as the mining activities are discontinued.
Highlights
Excavation of laterite, sand, kaolin, gravel, clay etc. for building purposes is common in many parts of Nigeria
Infiltration rate generally decreased with time, prior to attaining the steady state (Fig. 5)
The results show that pH, cation exchange capacity (CEC) and % base saturation had low variability (CV ≤ 15 %) down the profile, as reported other researchers (Ezeaku et al, 2015)
Summary
Excavation of laterite, sand, kaolin, gravel, clay etc. for building purposes is common in many parts of Nigeria. The need for sand and laterite for building, backfills and road construction is on the increase due to massive infrastructural development in Anambra state, Nigeria. This has led to increased intensity of land degradation in the state. The environmental degradation extends beyond the excavation of both surface and subsurface areas of the soil. Disturbance such as excavation or land levelling would alter the soil profile by destroying vegetation, root channels and soil horizons which would affect the sustainable use of the soil. The open pit system/method used in the mining has resulted to land degradation and interference with alteration of the soil profile. This method generates material debris called overburden which reduces the quality of the land (Ladan, 2004)
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