Classification and Suitability Evaluation of Soils of Nkpa, Bende LGA, Abia State Nigeria for Maize (Zea mays L.) and Groundnut (Arachis hypogea) Cultivation

A study was aimed at characterizing and evaluating the suitability of the soils of Nkpa for maize and groundnut cultivation. A Free survey method was adopted. Transects and soil augering were used to identify two soil units (MU 1 and MU 2). Four profile pits namely NK 01, NK 02, NK 03 and NK 04 were dug and characterized for morphological, physical and chemical properties. The results of the soil characterization indicated that all the soil units occurred on level or nearly level physiography, deep (> 100 cm) and well drained. (MU) 1 had surface soils characterized by Black (5 YR 2/1) and Light brown (7.5 YR 6/4) colour notations. The subsurface soils (MU 1) were characterized by yellowish red and reddish brown (5 YR 4/3 and 5 YR4/6) with redoximorphic features characterized from few, medium and faint pale brown (10 YR 6/4) to few, fine and faint reddish yellow (7.5 YR 5/6).  (MU) 2 had matrix colour ranging from dark reddish brown 5 YR 4/2 and greyish brown 10 YR 3/2 at the surface over reddish brown (2.5 YR 7/3) to yellowish brown 10 YR 3/6 at the subsoils. The soils were generally acidic (pH 5.0 – 5.8). Total nitrogen content was low to moderately low in MU 01 (0.05 – 0.13 %) and low to high for MU 02 (0.08 – 0.44 %) Available phosphorus content of the soils was moderately low 9.10 – 15.40 mgkg-1 (MU1) and moderately low to high 16.10 – 33.20 (MU 2).  Exchangeable k content was low 0.09 – 0.21 cmolkg-1 (MU 1) and low to moderate 0.17 – 0.58 cmolkg-1 (MU 2). The soil Orders identified in the area were Alfisols and Ultisols according to USDA and correlated to Luvisols and Acrisols of WRB. The aggregate suitability by parametric square root method indicated that the soils of MU 1 were marginally suitable (S3) but potentially moderately suitable (S2) while MU 2 had high (S1) and moderate (S2) suitability for maize but moderate (S2) and marginal (S3) suitability for groundnut production. Potentially, both maize and groundnut had moderate (S2) and high (S1) suitability with fertility as limiting factor for their cultivation in the area. It was concluded that low acidity and fertility are the major constraints of the soils for maize and groundnut cultivation in the area. Consequently, the soils of Nkpa, Bende LGA, Abia State Nigeria will require the application of lime, organic and inorganic manure and continuous periodic evaluation for sustainable production of maize and groundnut.