Effects of parkland agroforestry on soil fertility indices in northern Katsina State, Nigeria

Agroforestry is widely recognized as a sustainable land-use system that improves soil fertility and ecosystem resilience, particularly in semi-arid environments. This study evaluated the influence of parkland agroforestry on selected soil fertility indicators in Northern Katsina State, Nigeria. Twenty-four composite soil samples (0–20 cm) were collected from parkland agroforestry systems and adjacent open farmlands in Dutsi, Daura, Baure, and Kankia Local Government Areas. Soil pH, organic carbon, organic matter, total nitrogen, available phosphorus, and exchangeable potassium were analyzed using standard procedures. A Soil Fertility Index (SFI) was computed from standardized soil variables. Data were analyzed using descriptive statistics, analysis of variance, and Tukey–Kramer post hoc tests, with statistical significance assessed at α = 0.05. Significant differences were observed among the location × land-use groups for all measured soil fertility indicators (p < 0.0001), with parkland systems generally recording higher values than adjacent open farmlands. The mean SFI was higher under parkland systems (0.57 ± 0.74) than open farmlands (−0.57 ± 0.43). These findings demonstrated that parkland agroforestry was associated with higher soil fertility, based on the measured soil fertility indicators and Soil Fertility Index. Promoting the retention and integration of indigenous trees in farmlands may therefore contribute to sustainable soil management in semi-arid northern Nigeria.