Analysis of Soil Fertility Status of Selected Farmlands in Jigawa State, North West Nigeria

Declining soil fertility resulting from continuous cultivation, inadequate fertilisation, and erosion is a major constraint on food crop productivity in the smallholder farming communities of Jigawa State, which lies within the semi-arid ecological zone of North West Nigeria. This study analyses the fertility status of soils from five farming locations representing different soil series and crop rotation histories. Soil samples are collected at 0-15 and 15-30 centimetre depths using soil augers from ten representative plots per location. Parameters analysed include soil pH, organic carbon content, total nitrogen by the Kjeldahl method, available phosphorus by the Bray-1 extraction method, exchangeable cations, cation exchange capacity, and base saturation. Micronutrient concentrations of iron, manganese, copper, and zinc are determined by atomic absorption spectrophotometry following DTPA extraction. Results are interpreted against critical nutrient limits for tropical soils and deficiency thresholds established for sorghum, millet, and cowpea, which are the dominant crops in the region. Spatial variability maps are generated for each nutrient parameter. Findings are expected to reveal widespread phosphorus and nitrogen deficiencies consistent with continuous cereal cultivation without organic matter amendment. Recommendations for site-specific fertiliser formulations are developed to support smallholder productivity improvement in the North West zone. Keywords: soil fertility, Jigawa State, available phosphorus, organic carbon, cation exchange capacity