SOIL FERTILITY STATUS AND MAPPING UNDER DIFFERENT LAND USE TYPES ALONG TOPOSEQUENCE IN DINSHO DISTRICT OF BALE HIGHLAND, SOUTHEASTERN, ETHIOPIA

Abstract

Soil fertility depletion is the major challenge for agricultural production in southeastern highlands of Ethiopia and particular in the study area. Inadequate information on soil fertility status is one of the main constraints for site-specific appropriated soil fertility managements in the study area. The study was conducted to assess soil fertility status and mapping under different land use types along toposequence in Dinsho District of Bale highland Southeastern, Ethiopia. Based on the information obtained from field survey during 2018 soil samples were collected randomly at three depths(0-20, 20-40, 40-60 cm) from the natural forest, grazing and cultivated land use types at three slope positions (upper, middle and lower)in three replications. A total of eighty one (81) soil samples were taken and analyzed following standard laboratory procedures. Data were analyzed using the three-way analysis of variation by SAS software, version 9.2. Soil fertility maps for the plow layer (0–20 cm) were prepared using IDW interpolation techniques in Arc GIS software 10.1. The results of this show that soil color was varied from black to dark brown for moist soil and dark brown to brown for the dry soil. The textural class was varied from clay to clay loam; mostly clay dominated at subsurface. Bulk density (BD) varied from 1.29 to 1.73 gcm-3 relatively high for soil of cultivated land and soil at upper slope of the respective land use types. Soil pH-H2O ranged from 5.02 to 6.25 were relatively high under natural forest land followed by grazing land while low under cultivated land and significantly increased with increase soil depth while decrease slope. Selected soil fertility parameters were varied from 64 to 6.25%, 0.04 to 0.66%, 14 to 20.58 mg kg-1 and 10.24 to 48.73 cmol (+) Kg-1 for OM, TN, Av.P and CEC, respectively. These soil fertility parameters were relatively high for soil of natural forest land while low in soil of cultivated land and high for soil of lower slope position than upper slope under all respective land use types. The status of exchangeable bases (Ca, Mg, K and Na) of the study watershed from soil fertility status point of view were moderated and relatively high for soil of the lower slope position under all respective land use types. The micronutrients (Fe, Mn, Cu and Zn) content of the soil were high to moderate for the study watershed. However, Cu and Zn were low for some area in the watershed which required amendment. Based on soil fertility status maps N, P, Cu, Zn containing and organic fertilizers with appropriate rate should be applied for soil of cultivated land. Further investigation and validation testes based on crop response with appropriate type and rating of fertilizer should be conducted.