Characterization, classification and suitability ratings of soils for rainfed rice production in Rukubi, Doma, Nasarawa State, Nigeria

Rice is an important annual crop in Nigeria. It is one of the major staples, which can provide a nation's population with the nationally required food. The objectives of this study were to characterize, classify and determine the suitability ratings of some soils of Rukubi for rainfed rice production. All the soil units were deep (150 – 199 cm), unit III soils were well drained, while units I and II soils were somewhat poorly drained. The soils had textures ranging between sandy clay loam and clay loam. The soils were well structured (strong coarse sub-angular blocky). Soil reactions were slightly acid (pH 5.12 – 7.15 in H2O). The organic carbon content of the soils were moderately low to high (1.03 – 1.62 %) in the surfaces, while low in the sub-surface horizons (0.50 – 1.60 %). The total nitrogen was low at the surface horizons and ranged between 0.01 and 0.16 %. The soils were dominated by Ca and Mg with values varying from 1.10 – 4.021 cmol/kg and 0.05 – 3.89 cmol/kg respectively. The available phosphorus was relatively high in the surfaces (4.10 – 11.8 mg/kg), but, much lower in the sub-surfaces (14.15 – 9.85 mg/kg). The percentage base saturation of the soil ranged from 47 % to 98 %. Based on the physical and chemical characteristics, the soils of unit I 1were classified as TypicEndoaquepts/ AndicFluvisols; unit II was classified as EutricEndoaquepts/ AndicCambisols and unit III as ArenicEndoaquepts/ EutricFluvisols. The characteristics of the soil units were compared with the land requirements for rice production. On suitability rating, all of the soil units highly suitable for rainfed rice production.