Spatial Multi-Criteria Evaluation of Land Suitability for Rainfed Cowpea (Vigna unguiculata L. Walp.) Production in Kambriwa, Kaugama LGA of Jigawa State, Nigeria

Improving cowpea productivity in the semi-arid Sudan Savanna requires spatially explicit information on land resources to support agricultural planning and soil management. This study evaluated the suitability of land for rainfed cowpea (Vigna unguiculata (L.) Walp.) production in Kambriwa, Kaugama Local Government Area, Jigawa State, Nigeria, using a Geographic Information System (GIS)-based Multi-Criteria Decision Analysis (MCDA). Fifty-six geo-referenced surface soil samples (0–30 cm) were collected and analyzed for selected physico-chemical properties. Continuous spatial distribution maps of the soil properties were generated through spatial interpolation and evaluated using cross-validation, while slope, topographic wetness index (TWI), rainfall, and temperature were incorporated from digital elevation and climatic datasets. The evaluation criteria were standardized using a suitability framework informed by FAO land-evaluation principles, crop-specific requirements, and established soil-fertility classifications, and weighted using the Analytical Hierarchy Process (AHP). The suitability analysis showed that sand (94.25%), soil pH (82.96%), exchangeable potassium (71.31%), slope (99.99%), TWI (97.35%), rainfall and temperature (100%), were predominantly highly suitable for rainfed cowpea cultivation. Conversely, available phosphorus and cation exchange capacity represented the limiting factors, with 29.65% and 19.50% of the study area classified as not suitable, respectively, while nitrogen was largely moderately suitable (75.12%). The final overlayed land suitability classified 132.49 ha (12.08%) as highly suitable (S1), 927.09 ha (84.52%) as moderately suitable (S2), and 37.31 ha (3.40%) as marginally suitable (S3), with no areas falling within the not suitable (N) class. The findings indicate that the study area has substantial potential for rainfed cowpea production, although strategic phosphorus fertilization and practices that improve soil nutrient retention may help address identified soil fertility limitations. The study demonstrates the applicability of GIS-based spatial MCDA for spatially informed land-use planning in semi-arid environments, while the interpretation of the resulting suitability classes should consider uncertainties associated with soil-property prediction and spatial interpolation.