TITLE:
Assessment of Dithionite and Oxalate Extractable Iron and Aluminium Oxides on a Landscape on Basement Complex Soil in South-Western Nigeria
AUTHORS:
Olayinka Olakunle Olatunji, Yetunde Oyeyiola, Gbade Oyewunmi Oyediran
KEYWORDS:
Plinthites, Sesquioxides, Toposequence, Dithionite Extractable, Oxalate Extractable
JOURNAL NAME:
Open Journal of Soil Science,
Vol.5 No.11,
November
23,
2015
ABSTRACT: The study investigats the morphological, physical and chemical
characteristic of a toposequence on basement complex in Ejioku area,
south-western Nigeria on latitude 07°28.675'N;
and longitude 004°07.219'E; 180 m above
sea level at the upper slope. It terminates at the valley bottom on latitude 07°28.756'N; and longitude 004°07.229'E; 175 m
above sea level. The topography of the site is moderately slope (not
greater than 10%). The aim is to examine the two forms of sesquioxides
(crystalline-dithionite extractible Fe & Al and amorphous-oxalate Fe &
Al) and their distribution on the toposequence. The crystalline form of Fe
oxide dominates all the positions and ranges from 7.2 g/kg at the valley bottom
to 444.3 g/kg at the crest compared to the amorphous forms that range from 2.7 g/kg
to 10.9 g/kg. The crystalline and amorphous aluminium oxide contents of the
soils are low (2.9 g/kg - 43.3 g/kg and 1.3 g/kg - 8.7 g/kg respectively).
There is significant negative relationship between Fed and Fed/Feo (r =-0.15; P n = 16). There is also a
correlation between Feo and Ald (r = 0.63; P n = 16), FeO and FeO/Fed (r = 0.44; P n = 16),
signifying a high level of weathering. The relatively high amount of Fed virtually at all the horizons indicates that the crystalline and less active
forms of the oxides exist more on the landscape and may be responsible for the
non-availability of some nutrient like phosphorus that may be sorbed to their
crystals lattice. All forms of Al in the soils are low especially, the oxalate
extractable forms, when compare with the dithionite extractable forms. However,
there is a significant correlation between Ald and Feo/Fed (r = 0.57; P