AGRICULTURAL POTENTIALS OF SOILS DERIVED FROM SELECTED PARENT MATERIALS ON THE JOS PLATEAU, NIGERIA

Abstract

The agricultural potentials of soils depend on their properties which are usually influenced by the Parent Materials (PMs). An understanding of the properties of soils from different PMs is required for effective management and utilisation. Despite the high agricultural prospects of the semi temperate climate of the Jos Plateau, limited information is available on the effects of the PMs on the agricultural potentials of the soils. This study was, therefore, conducted to characterise, classify and assess the agricultural potentials of soils resulting from three major PMs (Basalt, Granite and Unconsolidated deposits [UD]) on the Plateau. A reconnaissance survey of the Jos Plateau was conducted to identify soils from the three PMs. One profile pit each was sunk and described at the crest, upper slope, middle slope, lower slope and valley bottom positions on two toposequences of soils formed on each PM, using standard methods. Randomised complete block design was used with three PMs as treatments replicated twice. Parent materials and soil samples were collected, assessed for morphological characteristics and analysed for physical and chemical properties, following standard procedures. These properties were used to classify the soils using USDA and FAO/World Reference Base systems while their agricultural potentials were assessed using Land Capability (LC) and Fertility Capability (FC) evaluation systems. Land capability was rated classes I (soils with few limitations), II (some limitations), III (severe limitations), IV (very severe limitations), V (limitations other than erosion hazards), VI (extreme limitations), VII (use restricted to grazing) and VIII (unsuitable). Fertility Capability was rated on specific constraints to soil fertility; the less the constraints, the better the soil. Data were analysed using descriptive statistics and ANOVA at 0.05. Basalt was fine grained, Granite and rock remnants of UD were coarse grained and their soils differed significantly in properties. Soils were red, strong brown and yellowish brown in colour on Basalt, Granite and UD PMs, respectively. The soils were well drained in the upper and middle slope positions and imperfectly or poorly drained in the lower slope and valley bottom positions. Total nitrogen was 1.32±0.75 g/kg, 1.47±0.82 g/kg and 1.08±0.62 g/kg for soils derived from Basalt, Granite and UD, respectively. Exchangeable potassium was significantly higher (0.63±0.38 cmol/kg) for the soils from Granite than those from Basalt (0.41±0.38 cmol/kg) and UD (0.37±0.34 cmol/kg). Effective cation exchange capacity was 10.78±6.2 cmol/kg, 15.24±3.6 cmol/kg and 15.48±2.88 cmol/kg for the soils from Basalt, Granite and UD, respectively. The soils from Basalt and Granite were classified as Inceptisols (Cambisols) and Alfisols (Lixisols); those from UD were Alfisols (Lixisols). In LC classification, class II land was 50%, 40% and 30% on Basalt, UD and Granite, respectively. Soils from UD had the least constraints to fertility (three), Basalt (four) and Granite (six), in FC classification. The soils of the Jos Plateau investigated were mainly Inceptisols (Cambisols) and Alfisols (Lixisols). Basalt and Unconsolidated deposits derived soils with minimal constraints had higher agricultural potentials than those from Granite and could support sustainable agricultural production with good management.