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Journal of Tropical Agriculture, Food, Environment and Extension

ISSN 1119-7455
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Article No 6 of Volume 3.1 (2004)

N. N. Oti

Deptartment of Soil Science and Technology

Federal University of Technology, Owerri



This study was conducted to evaluate the effect of natural in-situ erosion on soil physico-chemical properties and to identify indicator variables associated with various degrees of erosion on a Southern Nigeria Ultisol.  A preliminary survey conducted in 1997 had delineated four erosion phases on a contiguous sloping land within a watershed.  The erosion classes were Non-eroded (NE), Slight (S), Moderate (M) and Severely eroded (Sv) based primarily on Ap horizon thickness. Field experiments and laboratory analysis were done in 1998/99.  Definite consistent relationships that were statistically significant were observed between erosion class and some soil physical and chemical properties of surface 0 – 10 cm layer.  Among these were silt/clay ratio which ranged from 0.29 in NE to 0.19 in Sv; fine sand/coarse sand ratio were 0.33 (NE), 0.31 (S), 0.17 (M) and 0.19(SV).  Soil organic carbon (SOC) declined from 1.01% in NE to 0.60% in Sv, and (Ca + Mg)/(Al + H) ratio used to infer nutrient imbalance also decline from 1.23 in NE to 0.43 in Sv.  Aluminum saturation percentage increased from 33% in NE to 60% in Sv, and Ca/Mg ratio from 1.14 (NE) to 1.62 (Sv). Pedotransfer functions suggested that erosion – induced soil alterations are more process based than simple factor dependent.     It is therefore recommended that in this environment the prediction of erosion hazard and the identification of erosion classes be based on discriminant analysis derived from silt/clay, fine sand/coarse sand, Ca/Mg, and (Ca + Mg)/(Al + H) ratios.  Soil organic carbon and Al+++ saturation are equally important indicator variables.

Key words: Erosion, Degradation, Pedotransfer Functions and Classification

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