PEDOGENESIS OF A LITHOSEQUENCE IN THE NORTHERN GUINEA SAVANNA OF KADUNA STATE, NIGERIA
PEDOGENESIS OF A LITHOSEQUENCE IN THE NORTHERN GUINEA SAVANNA OF KADUNA STATE, NIGERIA
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Date
2012-06
Authors
LEMUEL, MUSA MANIYUNDA
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Abstract
Lithosequence of soils developed on four basement complexes, namely Older
Granites (OG), Quartzites (QZ), Mica Schists (MS) and Migmatite Gneiss (MG) was
conducted on crest position in the Northern Guinea Savanna of Kaduna State, Nigeria
with a view to explaining their pedogenesis. Three pedons were dug on each parent
material. Soil morphological, physicochemical and mineralogical properties were
examined and classified for their sustainable uses. Results indicated that soil
morphological properties were generally similar, except for variation in depth and
structure. The soils were generally deep to very deep (135 – 190cm), but had
restrictions due to parent materials on quartzite and mica schist (QZ1, MS2 and MS3)
and presence of plinthite on migmatite gneiss. Dark brown colour dominated the
surface, while strong brown in subsurface horizons with wider variation in the deeper
subsurface horizons (10YR, 7.5YR and 5YR). Texture of surface soil was sandy loam
and was attributed to erosion and eluviation of clay resulting in textural variation with
soil depth. The subsoils had clay to sandy clay with sandy clay loam in the deeper
portion of the subsurface horizons. The soils were dominated by sub-angular blocky
structure except soils on mica schist which had platy structure in the subsoils. Sand
dominated fine earth portion of the soils (ranged between 271 and 691 gkg-1) and their
subfractions were significantly influenced by parent materials and horizon
differentiation. Particle density varied between 2.56 and 2.68 Mgm-3 and bulk density
between 1.34 and 1.79 Mgm-3 in the soils. Water retention difference was generally
slightly low and varied between 0.64 and 33.26 cm. Parent materials had significant
influence on some chemical properties such as exchangeable Ca, TEB, EA, CECs,
base saturation and ESP. Higher values of exchangeable Ca, TEB, EA, CECs and
base saturation were in soils developed on MS followed by OG and QZ and least
values were in soils on MG. These variations were attributed to leaching of bases and
difference in pedogenic development (age). The chemical properties of the soils
indicated strongly acid to neutral pH (5.30 - 6.90). Total exchangeable bases ranged
between 2.92 and 8.98 cmol (+) kg-1, cation exchange capacity (CEC - NH4OAc)
were low to high, and moderate base saturation dominated the soils. The values of
organic carbon (10.00 gkg-1) and total nitrogen (1.00 gkg-1) were generally low.
Micronutrients (available and total forms) were all in adequate quantity, with
available Fe, Mn and total Zn significantly influenced by parent materials. Parent
materials and pedogenesis significantly influenced pedogenic forms of iron oxide and
crystallization was in the order of soils on mica schist < quartzites < older granite <
migmatite gneiss, whereas forms of manganese oxides were significantly influenced
by horizonation. Kaolinite, diaspore, muscovite and illite dominated the mineralogy
of clay fraction of the soils. Nature and extent of weathering of parent materials
caused variation in mineralogy of the soil and their moderate pedogenic development.
Mineral composition reflected soils on migmatite gneiss as most weathered and those
on mica schist as least weathered. Contents of major and trace elements (total oxide)
in the soils were not significantly influenced by difference in parent material, except
for K2O (P < 0.05), TiO2 and Cr2O5 (P < 0.01). Parent materials significantly
influenced relative weathering intensity of most total elemental oxides, with
significantly lowest relative retention mostly in soils on MG and highest in soils on
MS, thus reflecting variation in their pedogenic development (age). Parent materials
and pedogenic age were prominent factors that affected soil properties, thereby
influenced their pedogenesis. The main pedogenic processes include weathering of
parent materials, relative accumulation and depletion of major and trace elements,
structural differentiation and plinthization, braunification, humification, melanization,
leaching, argilluviation, desilication, allitization and ferritization. According to the
USDA Soil Taxonomy, all the pedons on migmatite gneiss were classified as Typic
Plinthustalf at the subgroup level. Pedons on mica schists MS1 and MS2 were
classified as Typic Haplustalf, while MS3 was classified as Kanhaplic Haplustalfs.
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Soils on quartzite were classified as Lithic Haplustalf (Pedon QZ1), Kanhaplic
Haplustalf (Pedon QZ2) and Typic Kandiustalf (Pedon QZ1). Pedons on older granite
were classified as Typic Kanhaplustalf (OG1), Typic Haplustalf (OG2) and Kandic
Paleustalf (OG3). In the World Reference Base Classification System, all the pedons
on older granite and quartzite were classified as Haplic Lixisol, whereas those on
migmatite gneiss as Plinthic Lixisol. Pedons on mica schist (MS1 and MS2) were
classified as Haplic Luvisols, whereas MS3 as Haplic Lixisol. Management options
suggested include construction of contour ridges and bunds, and cultivation of cover
crops. Effective post harvest crop residue incorporation, application of farm yard
manure and incorporation of legumes in crop rotation fields, as well as use of organomineral
fertilizers will sustain the soils for crop production. Fertilizer application
should be timely in judicious quantity and by burying to remedy their deficiencies.
Description
Thesis submitted to The School of Postgraduate Studies in partial fulfillment of the
requirement for the award of the Degree of Doctor of Philosophy (Soil Science)
Keywords
PEDOGENESIS,, LITHOSEQUENCE,, NORTHERN,, GUINEA,, SAVANNA, KADUNA STATE,, NIGERIA.