Characterization, Classification and Micronutrients contents of three Pedons overlying Calcareous Mudstone in a Tropical Rainforest of Nigeria

Abstract

Soils overlying calcareous mudstone in the tropics have peculiar characteristics and are rarely studied. The
study was designed to evaluate the soils based on their morphological, physical and chemical properties, and
relate these properties with soil micronutrients. The soils were also taxonomically classified using the USDA
Keys to Soil Taxonomy. Correlation analysis and descriptive statistics were adopted in the interpretation of
data using the R software. The contour map of New Netim was generated in the ArcGIS 10.8 environment and
the profile graph plotted out. One profile pit was sunk along each elevation range using free survey technique,
to represent soils in the highest (P1), mid (P2) and lowest (P3) elevations. The fairly deep to deep soils (60-163
3
cm) were loamy in texture with the dominance of silt and sand over clay, and low bulk density (1.2-1.6Mg/m).
Soil pH (HO) ranged from 7.1 to 8.04, while organic C and total N were 0.49-2.41 and 0.01-0.21%,2
respectively with values that regularly decreased with increased soil depth. The soil cation exchange complex
2+ 2+
was dominated by Ca (7.02-61.0 cmol/kg) and Mg (0.4-17.7 cmol/kg), while base saturation was > 50 %.c c
Available Fe, Mn, Cu, Zn and B were less than their respective world-wide agricultural and environmentally
acceptable values with ranges of 94.8-162.3, 21.5-159.8, 1.8-3.31, 2.6-4.8 and 1.6-2.34 mg/kg, respectively.
CEC and exchangeable Ca correlated negatively with extractable Zn (p<0.01), while total porosity correlated
positively (p=0.01, 0.05) with all the micronutrients studied except Boron. By the USDA System, P3 was
classified as Oxyaquic Hapludalf, while P1 and P2 qualified as Typic Hapludalf. P1, P2 and P3 were correlated
as Chromic Luvisol (Ochric, Profondic), Rhodic Luvisol (Ochric, Loamic) and Haplic Luvisol (Loamic,
Ochric, Profondic), respectively by the World Reference Base for Soil Resources System. The concentration of
available Fe, Mn, Zn, Cu and B were lower than world-wide ranges and are not likely to be injurious to crops in
the study area.