Quantitative Evaluation of Soil Fertility Status along the Nwaorie Riverbank using the Nutrient Index Approach

Abstract

Soil fertility is a critical determinant of agricultural productivity and ecosystem sustainability, particularly in riverine environments where alluvial deposits can enhance nutrient availability. This study assessed the fertility status of soils along the Nwaorie Riverbank in Owerri, Imo State, Nigeria, using the Nutrient Index (NI) approach. Systematic soil sampling (0–20 cm) was conducted across five zones, with laboratory analyses measuring pH, exchangeable potassium (K⁺), total nitrogen (TN), organic matter (OM), and available phosphorus (Av.P). Descriptive statistics, ANOVA, and Pearson correlation were employed to evaluate spatial variability and interrelationships among soil properties. Results indicated that soil pH ranged from 7.0 to 7.5, reflecting neutral to slightly alkaline conditions conducive to nutrient availability. Nutrient concentrations varied significantly across sites: Second Inland exhibited the highest NI (2.60), classifying it as high fertility, while Amakaohia had the lowest NI (1.80), indicating medium fertility. Strong positive correlations were observed among TN, K⁺, and Av.P, suggesting synergistic nutrient enrichment from alluvial deposition and anthropogenic inputs, whereas weak correlations with OM and pH indicated limited influence of soil reaction and organic matter on nutrient availability under current conditions. The findings reveal marked spatial heterogeneity in soil fertility, highlighting areas with nutrient limitations that require targeted management. The study underscores the importance of site-specific soil management strategies to enhance crop productivity, optimize nutrient use, and support sustainable land use planning in riverine environments.