SPATIAL VARIABILITY OF TOTAL NITROGEN IN TOPSOIL AND ITS RELATIONSHIP WITH SOIL PHYSICOCHEMICAL PROPERTIES UNDER DIFFERENT LAND USE TYPES IN THE ISHËM RIVER BASIN, ALBANIA

Abstract

Soil nitrogen plays a fundamental role in maintaining soil fertility, supporting ecosystem functioning and sustaining agricultural productivity. Understanding its spatial distribution and relationship with soil properties is essential for improving soil management in Mediterranean environments. This study aimed to characterize the physicochemical properties of topsoil in the Ishëm River Basin, Albania, investigate the relationship between total nitrogen (TN) and soil organic matter (SOM) and evaluate differences in TN concentrations between agricultural and naturally vegetated soils. A total of 24 composite topsoil samples representing agricultural and naturally vegetated soils were collected and analyzed for pH, electrical conductivity (EC), soil texture, SOM, TN, ammonium (NH₄⁺-N), nitrate (NO₃⁻-N) and total phosphorus (P-tot). Total nitrogen concentrations ranged from 448.78 mg kg⁻¹ to 3617.42 mg kg⁻¹, with a mean value of 1503.01 mg kg⁻¹, indicating substantial spatial variability across sampling sites. A strong linear relationship was observed between TN and SOM (R2 = 0.93), showing that higher TN concentrations were closely associated with higher SOM content. Mean TN concentrations were slightly higher in agricultural soils (1523.04 mg kg⁻¹) than in naturally vegetated soils (1482.98 mg kg⁻¹); however, the difference was not statistically significant (Welch’s t = 0.129, df=14, p = 0.899). These findings provide baseline information on soil nitrogen status in the Ishëm River Basin and support future soil monitoring and management studies.