Impacts of Area Closure on Selected Soil Physicochemical Properties at Meldam Watershed, Sekota Area, North Western Ethiopia

Abstract

Area closure, by excluding human and animal interference, has proven to be an effective conservation strategy that facilitates natural regeneration, improves soil health, and enhances ecosystem resilience in degraded landscapes. This study evaluated how area closure influences key soil physicochemical properties critical for restoring degraded lands in the Meldam sub-watershed, Northwestern Ethiopia. Eighteen plots (9 from grazing land and 9 from area closures), each 20 x 20 m, were established across three slope positions with three replications along six transects. From each plot, one composite soil sample (for TN, avP, CEC, EC, exchangeable bases, pH, and SOM) and one undisturbed sample (for BD) were collected from a 0-20 cm depth. In total, 18 soil samples (9 from open grazing and 9 from area closures) were analyzed. Paired t-tests (at 1% significance) using SAS 9.3 assessed differences across land use and slope positions, while Pearson correlation evaluated relationships among soil properties. Ordinary kriging was used to map the spatial distribution of soil physical and chemical properties across different land uses. The results indicated that most soil properties improved following the conversion of open grazing land to area closure. Compared to grazing lands, bulk density and sand content decreased in area closures and lower slope positions, while clay content and soil moisture increased. Soil organic carbon, total nitrogen, available phosphorus, and cation exchange capacity rose by 73.15%, 34.78%, 64.13%, and 63.32%, respectively, in area closure and lower watershed areas. Base cations also showed similar improvements under closed land conditions. Soil fertility restoration was more pronounced on lower slope positions than upper ones. These findings highlight area closure as an effective approach for rehabilitating degraded soils, supporting its expansion within the study area and in similarly affected regions.