Journal of Agricultural Science and Practice

The ever-mounting population pressure on the land of old Imo State of Nigeria necessitated a re-evaluation of the soils using data from the reconnaissance soil survey of the location produced in 1985, and which has remained the major source of soil information for the location. The exercise involved updating the soils' classifications using later editions of USDA Soil Taxonomy and FAO World Reference Base (WRB), as well as determining the soils’ Fertility Capability Classifications (FCC) and suitability ratings. The soils’ parent materials were classified into sandstone (st), sand and sandstone (sst), shale and sandstone (shs), shale (sh), coastal plain sands (cps), and Alluvium (Al). However, updating the soils’ classifications taxonomically, more classes of soils were recognised than was originally the case. The major classes by USDA Soil Taxonomy were Typic Paleudult, Kandic Plinthaquult, and Typic Paleudalf; while for the WRB, they were Acrisol, Nitisol, Lixisol and Cambisol. By the FCC, loam dominated all soils at the Type level. At the Substrata type level, clay dominated the shale derived soils, while loam was still dominant for the other soils. Physical barriers – d(dryness), g(gley), r⁺ (gravel) – were mainly with shale, while the chemical constraints – a (Aluminium toxicity), k(low nutrient capital reserve), e(low cation exchange capacity) – were more with the sandy parent materials. Using soil texture, the fertility indices of the soils rated moderately suitable (S₂) for the shale derived soils but marginally suitable (s₃) for soils of the other parent materials thus: Sh (75%, S2), > ShS (65.3%, S2),  > AL (40.3%, S3) > CPS (32.9%, S3), > St (31.9%, S3) > SSt (29.9%, S3). There is a relationship between parent material and soil fertility. When only legacy data is available, geological formations in the location should guide the grouping of the soils for effective management. There is a need to sample the soils again.