Soils of Khana Local Government Area of Rivers State, Southern Nigeria were evaluated using semi detailed soil survey for citrus cultivation. The purpose of this research was to evaluate the suitability of soils of the study area for the cultivation of citrus. The total land area covers 49,631.54 ha and was delineated into eight mapping units based on the soil types. One pedon each was dug in each mapping unit and described using the FAO system. The nonparametric method of soil suitability evaluation was used. Four soil orders, majorly Inceptisols/Cambisols, Entosols/Arenosols, Ultisols/Acrisols, and Alfisols/Lixisols, were identified in the area. The results showed that land requirements/characteristics such as climate (mean annual rainfall), wetness (depth to water table) and fertility made the land marginally suitable (S3) to not suitable (N) for citrus cultivation across the eight pedons. The three limitations for citrus cultivation in the area are climate (annual rainfall), wetness (depth to the water table) and fertility (low status of NPK and pH). The land is potentially suitable for citrus cultivation but currently marginally and not suitable due to these three limitations.

This study was conducted to characterize and classify the soils of the Teaching and Research Farm, Rivers State University, Port Harcourt, covering 30 hectares of land area. A rigid grid soil survey method at a very detailed level (100 × 100) m² (1 ha) with two mapping units identified and delineated. Each of the mapping unit was represented by a soil profile described from the lowest end to the upper part of the profiles to avoid contamination. Soil samples were collected for laboratory analysis from the various horizons identified. The results obtained, indicated that the soils were of Inceptisols/ Cambisol order, Udepts at the suborder level, Eutrudepts Great group level and Typic Eutrudepts (subgroup level). Thus, the drainage, parent materials, climate (rainfall), and vegetation of the area along with the geologic material, formed from the sedimentary rocks that were weathered into coastal plain sands and buried under alluvium at various degrees at different locations in the study area, greatly affected the soils of Teaching and Research Farm, Rivers State University, Port Harcourt, which are primarily Inceptisols/ Cambisols.

The research was carried out in Bodo city in Gokana Local Government of Rivers State, Southern Nigeria to evaluate the land suitability for rubber and cashew cultivation using the relevant land suitability guidelines for the cultivation of the two cash crops of interest. Mapping of the 100 ha of land in Bodo city was done using the rigid grid method of soil survey. The three mapping units (summit, middle slope and valley bottom) were identified and delineated. Three representative soil pedons of 2 m x 2 m x 2 m were dug and described by horizon from top to bottom (0 cm to 200 cm). Soil samples were collected from identifiable horizons and processed for laboratory analysis using standard routine laboratory methods most appropriate. The results showed that pedons 1 and 3 covering 86,000 ha of the entire study area were found to be moderately suitable for rubber cultivation with limitation in soil physical characteristics (texture) and fertility (low base saturation < 50 %). Pedon 2 covering 14,000 ha of the total land of the study area was marginally suitable due to limitation in soil fertility (low base saturation < 80 %). Pedon 1, 2, and 3 were also moderately suitable for cashew cultivation in the study area with limitation in soil physical characteristics (texture) and fertility (low organic carbon), while limitation in wetness (poor drainage) was peculiar to pedon 3 only. Thus, soils in the study area were moderately suitable for both rubber and cashew cultivation in the area.