Soil classification and suitability evaluation are requirements for attaining optimum utilization of the available land resources. Detailed soil survey of  a top sequence at Alabata, Southwest Nigeria was carried out using the rigid grid method. The soils were characterized, classified, and evaluated for rain-fed rice production. The results of the study showed that the soils were loamy sand to sandy clay loam texture, fine to coarse sub-angular blocky structure and loose to hard consistency. Soil reaction ranged from strongly acidic to slightly acidic (pH 4.2-6.1) with low organic carbon (5.6-19.0 g/kg) and total nitrogen (0.5-1.7 g/kg). The potassium contents were moderate while exchangeable cations and available phosphorus were  very low. Pedon 1 was classified as KandicPaleustalfs, pedon 2 as TypicHaplustalfs and pedon 3 as Aeric Kandiaqualfs. The index of current productivity (IPc) by linear model ranged between 8.7 and 10.3, while by square root models ranged between 16.2 and 17.5. The values suggested that the soils were not currently suitable (N2 and N1) for rice production. The index of potential productivity (IPp) ranged from 48.5 to57.0 by linear model and from 53.9 and 58.5 for the square root model. Thus, pedons were potentially marginally (S3) and moderately (S2) suitable for the production of rice. The limiting factors were mainly low levels of macro nutrients, organic matter and cation exchange capacity. Key words: Classification, climate, suitability evaluation, toposequence, rice production

The assessment of degradation status of wetland soils under five different land use types (LUTs) in Ogun state, Nigeria were studied. The laboratory study was conducted to determine the physical, chemical and biological properties of these wetlands and the results obtained were compared with the food and agriculture organization (FAO) standard indicators and criteria for land degradation assessment. The textural composition of the soil ranged from sandy loam to sandy clay loam. Total porosity was generally low with the mean value of 40.5%. The pH ranged from moderately acidic to slightly alkaline with fallow soil having the highest value. Available phosphorus was low across the LUTs. Total nitrogen was predominantly low in most of the cultivated soils to moderate in the fallow soils. Cation exchange capacity (CEC) was low, while the exchangeable sodium percentage (ESP) was high (>5) in all the LUTs. The organic matter ranged from low to moderate indicating low nutrients status of the soil. The soils were classified and placed in the order Alfisols. The degradation results showed that most of the cultivated wetlands were highly degraded compared to the reference (fallow) soils which were slightly degraded. It is opined that soil conservation practices like the use of inorganic fertilizers, organic manure, and composts should be intensified in these fragile low fertile wetlands. Also, there should be a periodic monitoring of the fertility status of the wetlands from the time it is first open for cultivation to subsequent uses.

Removing forest cover for oil palm plantations has raised questions about climate change problems and debates and their associated impacts. The design of the pruned fronds of the trees does not make them ideal for use as mulch cover on the entire farm, but they are heaped between the plant rows. This research investigated the changes in the physicochemical properties of soils under oil palm plantations of different ages. Soil surface (0-20 cm) and subsurface (20-40 cm) samples have been obtained from various ages of oil palm plantations (0-5, 5-10, 10-15 and, 15-20 years). Two distinct samples were taken on the same farm, under alleys and heaped pruned fronds. Soil samples used as a standard (control) were collected from adjacent forest land. Analyses of particle size showed that the soils were sandy loam to sandy clay loam texture soils. Bulk density was low and varied with age and depth. The soils were moderate to slightly acidic pH, relatively low organic carbon, total nitrogen, and available phosphorus contents. Based on the standard ratings, exchangeable bases and cation exchangeable capacity content were also low, while high percent base saturation was observed. Research findings have shown that the soil properties of different ages of oil palm plantations vary and should therefore be handled differently based on of their characteristics. Accumulation of organic residue on the floor of the plantations should be encouraged as this will help to increase organic matter levels.

A study was conducted to examine the impact of land use and agrochemicals on wetland soil quality of Odeda Farm Institute, Eweje, Ogun State, Nigeria. The land use types studied were maize, plantain, rice, vegetable, and fallow. Five profile pits were dug, four at agrochemicals applied fields and one at fallow field as control. The results showed that soil texture was not influenced by land use and agrochemicals. The particle size distribution data showed that the soils consisted of high sand content (>600 g/kg). Soil pH, organic carbon and total nitrogen were low at agrochemicals applied fields when compared with the fallow field. The reverse is the trend for available P which is low at the fallow field due to non application of phosphate fertilizer. The heavy metals (Cd, Cu, Fe, Mn, Pb and Zn) results differed significantly (p<0.05) between the agrochemicals applied fields and the fallow field. Soil nutrients depletion and heavy metal accumulation were very prominent under agrochemicals applied fields. However, the impact of land use and agrochemicals which mostly accounted for major changes in the soil quality indicators can be immediate or long term, and wetland users should take into consideration long effect of current land decisions.