Suitability Assessment of Soils Supporting Oil Palm Plantations in the Coastal Plains Sand, Imo State, Nigeria

Due to the declining yield of Oil palm, soils of the coastal plains sand of Imo State supporting oil palms were evaluated. A bulked sample was taken from each of the ten sites studied, at 0 – 20cm and 20 – 40cm depths and analysed in the Laboratory. Soils textures were dominated by sandy loam at the surface, but sandy clay loam at the subsurface. Ranges of values of parameters at the topsoil were: pH(4.1 – 5.6), ECEC (5.7 – 8.7cmol/kg), BS (36 – 87%), OM (1 – 4.7g/kg), TN (0.01 – 0.14g/kg), Av. P (6 –48mg/kg), Fe (0 – 233mg/kg), Cu (0 – 1.2mg/kg), Zn (0.3 – 14mg/kg), Mn (5.7 – 145.6mg/kg). Fertility Capability Classification (fcc) identified in the soils the condition modifiers – g (gley – in the valleys), e (low CEC), h (strong acidity), and k (low content of k). But by suitability rating, the main limiting factors were – OM (N), TN (S3/N), K (S3/S2). Generally, the soils were moderately suitable (S2) for oil palm cultivation. Slight drainage of sites on alluvium, moderate liming (particularly of alluvial soils), liberal application of nitrogenous fertilizer and moderate application of potassic fertilizer are recommended. The parametric method of assessment was more realistic than the non-parametric.