ABSTRACT

Two forms of sesquloxides, DCB — Fe and Al and oxalate Fe and Al were analyzed to determine their distribution on pedons along a typical toposequence located in the coastal plain sand parent material of south Eastern Nigeria. The pedons were located at the crest (1), upper slope (2), middle slope (3), lower slope (4) and valley bottom (5) positions. The oxalate — extractable Fe oxides values ranged from 0.03 to 1. 14%Fe2O3with a mean of 0.28% Fe2O3while the oxalate — extractable Al oxides values ranged from trace to 0.12% A1203with a mean of 0.07%. The DCB — Fe values ranged from 0.60 to 7.49% Fe2O3with a mean of 2.28% while the DCB. Al values ranged from 0.34 to 1.78% A1203 with a mean of 0.82%. The proportion of amorphous Fe2O3 indicated by the "active" ratio (oxalate-Fe /DCB-Fe) was higher in the poorly drained soils than well — drained soils. The 'active' ratio in the well-drained soils ranged from 0.01 to 0.33 with a mean of 0.13 while the poorly drained soils values ranged from 052 to 0.72 with a mean of 0.62. The 'active' ratio for % A1203ranged from 0.01 to 0.42 with a mean of 0.12. The 0GB Fe showed no significant relationship with any soil properties but the DCB—AI showed significant negative relationships with both % sand and C/N ratio (r = - 0.42 and r = - 0.40, p<0.05) respectively, it also showed a positive relationship with %clay (r=0.42, p'<0.05). The oxalate — Fe showed a negative significant relationship with % clay (r = - 0.53, p<0.01), while the oxalate — Al showed a negative significant relationship with % BS (r = - 0.66, p<0.01). There was a co-migration between % clay and DCB-Fe in the well-drained pedons but none in the poorly drained pedon.