Characterization and Assessment of Soil Acidity Status Under Different Land UseTypes and Soil Depths in Lalistu Cheri Watershed, Sibu Sire District, Western Ethiopia

Abstract

Soil acidity, a significant form of chemical soil degradation, is one of the most pressing challenges in Ethiopia, particularly in the highlands. It severely impacts agricultural <i>productivity</i> across much of the country<i>. Owing to its impact on crop production and productivity, it is a critical issue that requires immediate attention in most highlands in Ethiopia. This study was conducted at the Lalistu Cheri watershed, which is located in the Sibu Sire District of the western zone of the Oromia region, Ethiopia, with the objective of characterizing and assessing the soil acidity status under different land use types and soil depths. Replicated composite soil samples were collected from three representative land use types (cultivated, grazing, and eucalyptus plantation lands) and two soil depths (0-20 and 20-40 cm) by X-patterns along transects and analyzed via standard laboratory procedures. </i>The results revealed spatial variation in the soil properties among the land use types and soil depths. The soils in both cultivated and eucalyptus plantation land were strongly acidic (pH<5.5), whereas those in grazing land were moderately acidic. The highest (54.89%) and lowest (43.73%) clay contents were recorded in the soils of cultivated and grazed lands, respectively, whereas the sand content was greater (36.11%) in the eucalyptus plantation land.<i> The relatively highest bulk density (1.36 g cm<sup>-3</sup>) was recorded in the grazed land soils, followed by the cultivated land soils (1.32 g cm<sup>-3</sup>). Both the exchangeable acidity and aluminum content in all land use types decreased with increasing soil depth, which was consistent with their acid saturations. The organic carbon content ranged from 2.30% at the subsurface layer of the cultivated land to 3.44% at the surface layer of the grazing land soils, whereas the total nitrogen content ranged from 0.19% to 0.30%. Available P ranged from 7.31 mg kg<sup>-1</sup> to 12.61 mg kg<sup>-1</sup>. The highest Ca, Mg, Na, and K contents (8.92, 5.76, 0.30, and 1.26 Cmol (+) kg<sup>-1</sup>, respectively) were recorded in the soils of the grazing land. The amount of PBS used ranged from 35.14% to 78.45%. The CEC and ECEC of the soils in the three land use types also increased consistently with increasing soil depth. </i>Micronutrient concentrations decreased with soil depth. The Fe and Mn contents<i> ranged from 0.54 and 4.42 mg kg<sup>-1</sup> in the subsurface layer of the grazing land and eucalyptus plantations, respectively, to 10.58 and 12.14 mg kg<sup>-1</sup> in the surface layer of the eucalyptus plantations and grazing land soils, respectively. Cu and Zn also ranged from 1.52 and 0.29 mg kg<sup>-1</sup> to 3.16 and 0.85 mg kg<sup>-1</sup>, respectively. The study suggests that both CL and EPL soils exhibit the highest acidity and require soil management practices, such as lime application, to reduce acidity and improve soil fertility. On the other hand, GL soils show more favorable conditions for nutrient retention and pH.</i>