Soil Fertility Assessment and Mapping under Different Land Use Types along Toposequence at Danka Watershed in Dinsho Districts of Bale Highland Oromia, Southeastern Ethiopia

Abstract

Soil fertility assessment and mapping bases, to increase fertilizer usage efficiency, decision-makers, planners, and soil management in undulating slopes farming of Ethiopian highlands like Bale Highland. The study aimed to assess and map soil fertility status along toposequence under different land use types at the Danka watershed of Dinsho District Bale Highland, Southeastern Ethiopia. Following the initial reconnaissance field survey, 54 composite soil samples were prepared from the three land use types (natural forest, grazing, and cultivated) at three slope positions lower (0 - 10%), middle (10 - 15%), and upper (15 - 30%) at a soil depth of 0 to 20 cm. Finally, the laboratory results were interpolated using the IDW interpolation technique in ArcGIS software 10.5 for the soil fertility status map and further analyzed using R software 4.1.1 Version for mean separation. The study findings indicate that the soil texture class of the study was loam to clay loam, clay loam, and clay to clay loam at the upper, middle, and lower slope positions, respectively. The finding revealed that the values varied from 5.81 – 6.66, 2.07 – 6.25%, 0.13 – 0.71%, 2.83 – 17.56 gm/kg, and 14.04 -38.80 cmol (+)/kg) for the soil pH, organic matter, total nitrogen, available phosphorus, and CEC, respectively. In this study, most of the soil fertility status of the Danka watershed was as follows: natural forest > grassland > cultivated land use types and lower slope > middle slope > upper slope positions. In conclusion, the main factors contributing to the area's declining soil fertility status were monocropping, total crop residue removal, soil erosion, nutrient leaching, and inadequate soil management. The results of the current study offer the basis for the work of farmers, planners, decision-makers, and other agriculture-related stakeholders. Integrated soil fertility management with biophysical soil conservation measures is advisable for cultivated land at all slope positions. Further, a study on slope position-based crop response fertilizer rating for agricultural precision and ensuring food security is recommended in undulating fields of the Danka watershed.