Abstract:
Evaluating the effect of land uses on the soil physicochemical properties and organic carbon stock under different land use types are crucial option for sustainable soil and land management, and fighting climate change by improving soil health and quality. In the Liben District of southern Ethiopia, a study was carried out to investigate the spatial variability of selected soil physicochemical properties and organic carbon stock under different land use types. In total, 81 undisturbed core and disturbed composite soil samples were collected with three replications from cultivated, grazing, and natural forest lands at three soil depths (0-20, 20-40, and 40-60 cm). Soil samples were analyzed at Haramaya University Soil Laboratory. Standard laboratory procedures were employed for the analyses of selected soil physicochemical properties and organic carbon stock. The analysis results were subjected to two-way ANOVA. Means comparison was determined using the least significant difference at 0.05 levels of significance. Statistical analysis revealed notable variations due to differences in land use types and soil depths. Cultivated and natural forest lands had the highest mean values of sand and clay, respectively. The soil texture class was sandy clay loam for all land use types and soil depths, but sandy loam for cultivated and grazing lands at 0-20 cm soil depth. Higher soil pH (8.18) was found in natural forests at 0-20 cm soil depth. The lowest soil organic carbon content was registered under cultivated land (1.49%) at 40-60 soil depth. The higher (0.22%) total nitrogen was found under natural forest land at 0-20 cm soil depth. The relatively higher available phosphorus content was found under natural forest land (4.54 mg kg-1 ) at 0-20 cm soil depth, indicating deficiency of available P in the study area. Relatively higher mean soil exchangeable bases were recorded under natural forest along all the soil depth. The higher CEC was obtained under natural forest (32.91 cmolc kg-1 ) at 0-20 cm soil depth; whereas the lower was obtained under cultivated land (24.67 cmolc kg-1 ) at 40-60 cm soil depth. Relatively higher mean PBS and ESP were recorded under natural forest along all the soil depth. Mean extractable micronutrients were relatively lower under cultivated land along all the soil depth. The obtained results were indicated iron and zinc deficiency in the cultivated land. The highest (61.31 t ha-1 ) soil organic carbon stock was found at 0-20 soil depth of natural forest land. Natural forest land contributed more soil organic carbon stock than grazing and cultivated land indicating that the appearance of tree on natural forest land was able to restore more CO2e from the atmosphere. Moreover, the highest (529.58 t ha-1 ) soil organic carbon stock was found under natural forest land followed by grazing land (447.56 t ha-1 ) and the lowest (382.12 t ha 1 ) was found under cultivated land. The result revealed that all soil physicochemical properties were higher in natural forest land and lower in cultivated land except for sand particle and bulk density which were higher in cultivated land and lower in natural forest land. Increase in the extent of grazing and cultivated land at the expense of forest cover associated with poor management has adversely affected the soil properties in grazing and cultivated lands. Therefore, reducing the land use change and adopting proper management practices of the soil are very crucial in order to reduce the effect of land uses on soil properties and organic carbon stock to meet climate smart agriculture goals.
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