Classification and suitability evaluation of soils along a toposequence for rice production in Alabata, Southwest Nigeria
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