No abstract

The study investigats the morphological, physical and chemical characteristic of a toposequence on basement complex in Ejioku area, southwestern 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 Fe d /Fe o (r = −0.15; P < 0.01; n = 16). There is also a correlation between Fe o and Al d (r = 0.63; P < 0.01; n = 16), Fe O and Fe O /Fe d (r = 0.44; P < 0.01; n = 16), signifying a high level of weathering. The relatively high amount of Fe d 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 Al d and Fe o /Fe d (r = 0.57; P < 0.01). As a result of high accumulation of crystalline form of Fe and Al oxide with increasing depth, most especially, at the crest/upper slope, there is greater amount of concretions, nodules and plinthites which will lead to further deterioration of the soil for agricultural purposes.

No abstract

The assessment of degradation status of soils in selected areas of Ogbomoso, Oyo state wascarried out. The soil physical and chemical properties were evaluated using mini pits and surface sampling. The laboratory results obtained were compared with the standard indicators and criteria for land degradation assessment according to FAO, 1979. The results revealed that most of the cultivated parts of the study sites were very highly degraded compared to the soil under vegetative fallow which were moderately degraded. The textural class of the soil ranged from loamy sand to sandy loam. Saturated hydraulic conductivity ranged from 1.54 to 3.4 cm hr-1 corresponding low to moderate permeability. Bulk density ranged from 1.53 to 1.60 g cm-3. Organic matter was very low in all the study sites. Available phosphorus was low in all the locations. Total nitrogen was predominantly low in most of the cultivated and fallow soils. Exchangeable Sodium Percentage (ESP) of the sites depicted that most of the soils were slightly sodic. Summarily, the soil physical and chemical properties status when compared with the FAO standard show that the area either cultivated or fallow is under degradation. In order to optimize crop production in these areas, there may be need to introduce soil conservation strategies. The practice may include use of crop residues, green manure or poultry manure to boost soil fertility. Also regular monitoring of the fertility status of the soils is required.

(82.4 and 88.4) and N-fixed (38.65 and 42.51