Spatial and Seasonal Variation in Irrigation-Water Quality and Soil Macronutrient Status in Selected Fadama Fields along River Chanchaga, Minna, Nigeria

Proper management of irrigation-water chemistry is important for maintaining soil quality and sustaining vegetable production in peri-urban fadama systems. This study evaluated spatial and seasonal variation in the physicochemical properties of irrigation water along an approximately 20-km corridor of River Chanchaga, Minna, Nigeria, and characterized the macronutrient status of associated cultivated soils. Water and topsoil samples were collected during the wet season (May–July 2025) and dry season (January–March 2026) from four river locations (L1–L4) and a comparative borehole irrigation-water source (C1). Water-quality data were evaluated using General Linear Models and two-way analysis of variance (ANOVA), whereas soil properties were interpreted descriptively because the field-level soil samples were composites rather than independently replicated observations. Dry-season electrical conductivity (EC) increased markedly across the monitoring locations, ranging from 1,201.33 to 1,365.33 µS cm⁻¹, corresponding to the FAO slight-to-moderate restriction category for irrigation use. Sodium Adsorption Ratio (SAR) remained low, ranging from 0.086 to 0.229, while chloride concentrations remained below the FAO guideline throughout the study period. The cultivated soils were predominantly sandy loam, with high sand content (80.00–81.80%), low soil organic carbon (0.56–0.76 g kg⁻¹), and low effective cation exchange capacity (4.60–6.17 cmol kg⁻¹). Available phosphorus was particularly low (0.22–0.92 mg kg⁻¹), while exchangeable potassium ranged from 0.04 to 0.15 cmol kg⁻¹. Total nitrogen ranged from 0.43 to 1.31 g kg⁻¹, whereas exchangeable calcium was the dominant measured base (2.54–3.85 cmol kg⁻¹). The findings demonstrate that seasonal changes in irrigation-water salinity occur alongside soil limitations associated with coarse texture, low organic-carbon status, low exchange capacity, and acidic soil reaction. Continued irrigation-water monitoring together with balanced, soil-test-based fertility management is therefore important for sustaining vegetable production within the River Chanchaga agricultural corridor.