The effect of exclosures on restoration of soil properties in Ethiopian lowland conditions

Abstract

Land degradation is one of the environmental challenges in the semi-arid areas of Africa such as Ethiopia. To tackle this problem, exclosures have been established on degraded open grazing lands. However, there was paucity of research regarding their ecological merits, especially in the lowlands of Tigray, Northern Ethiopia. Hence, this study was conducted to explore the effect of conversion of grazing lands to an exclosure on soil chemical properties and soil organic carbon stock (SOC stock) in Tselemti district, which was taken as testing site to represent the lowlands of Tigray. A total of 36 plots (18 from grazing land and 18 from exclosure), measuring 20 m × 20 m, were established along 6 transects for soil sampling. From each plot, 1 composite soil sample for analyses of total nitrogen (TN), available phosphorus (avP), cation exchange capacity (CEC), electrical conductivity (EC), available potassium (avK), soil pH and soil organic carbon content (SOC) and 1 undisturbed soil sample for soil bulk density (BD) determination was collected from a depth of 0–30 cm. Hence, a total of 72 soil samples (36 for nutrients and 36 for bulk density analysis) were analyzed in the laboratory. Paired samples t test statistics at 5% level of significance using SPSS version 20 was used to compare the land uses. Pearson correlation test was also used to analyze the relationship among the different soil properties. The study showed that the conversion of open grazing land to an exclosure enhanced most of the soil properties except soil pH, avP and EC. The results revealed that the exclosure had significantly (p < 0.05) higher SOC (1.89 ± 0.1 and 1.29 ± 0.06) and SOC stock (73.61 ± 4.9 and 45.64 ± 2.57 Mg ha−1), indicating an improvement by 46.5 and 61.3% as compared to the grazing land. Similarly, it enhanced CEC, TN and avK level significantly (p < 0.05) by 16.8, 45.5 and 34%, respectively. It can be concluded that conversion of open grazing lands to exclosures is a viable option to restore degraded soils. For this reason, additional exclosures have to be established on previously degraded open grazing lands in the area and areas with similar biophysical setup.