open access

Submitted: 2026-02-22
Crop Production and Environment
Published: 2026-03-30

Comparative assessment of soil fertility status in irrigated and rainfed agricultural systems in northern Nigeria

Department of Soil Science, Audu Bako College of Agriculture, Dambatta, Kano State, Nigeria
Department of Soil Science, Faculty of Agriculture, Bayero University, Kano, Nigeria
Department of Soil Science Aliko Dangote University of Science and technology Wudil, Kno State, Nigeria

Abstract

Soil fertility decline constrains agricultural productivity in sub-Saharan Africa, yet comparative assessments of fertility status between irrigated and rainfed systems in Northern Nigeria remain limited. This study compared soil fertility status between irrigated and rainfed agricultural lands in Dawakin Kudu Local Government Area, Kano State, to identify system-specific fertility constraints and inform targeted nutrient management strategies. Sixty soil samples (30 from each system) were collected using systematic grid sampling (200 m × 200 m) at 0-20 cm depth. Soil texture, pH, organic carbon (OC), total nitrogen (N), available phosphorus (P), exchangeable bases (Ca, Mg, K, Na), exchangeable acidity (EA), and effective cation exchange capacity (ECEC) were analyzed. Micronutrients (Zn, Cu, Mn, Fe) were extracted using DTPA and analyzed by atomic absorption spectrophotometry. Fertility status was classified using Esu (1991) rating criteria for Nigerian Savanna soils. Data were analyzed using descriptive statistics and independent samples t-tests. Both systems exhibited sandy loam texture (mean sand 60.7-60.8%, clay 15.9-16.2%) with slightly acidic pH (6.05-6.15). Critical fertility limitations were identified in both systems: organic carbon (0.68-0.76%, rated LOW), total nitrogen (0.06-0.07%, LOW), available phosphorus (4.03-4.05 mg/kg, LOW), and effective cation exchange capacity (4.26-4.45 cmol(+)/kg, LOW). Exchangeable bases showed medium ratings: Ca (2.61-2.74 cmol(+)/kg), Mg (0.75 cmol(+)/kg), and K (0.22-0.27 cmol(+)/kg). Exchangeable acidity was significantly higher in irrigated (0.65 cmol(+)/kg) than rainfed systems (0.39 cmol(+)/kg). Micronutrients were rated HIGH in both systems: Zn (16.5-18.9 mg/kg), Cu (2.50-2.79 mg/kg), Mn (31.6-34.1 mg/kg), and Fe (177.0-192.4 mg/kg), indicating no micronutrient deficiencies. Both irrigated and rainfed systems face similar critical macronutrient constraints (OC, N, P) and low nutrient retention capacity (ECEC). Irrigation did not markedly improve macronutrient fertility status but significantly increased soil acidity. The low phosphorus availability despite high iron concentrations suggests P fixation by iron oxides. Integrated soil fertility management focusing on organic matter restoration, phosphorus availability enhancement, and nitrogen supplementation is essential for both systems. Micronutrient fertilization is not a priority.

Keywords: Soil fertility, irrigation, rainfed agriculture, tropical soils, Esu rating, Nigeria, organic carbon, phosphorus deficiency, micronutrients