ASSESSMENT OF SOIL FERTILITY STATUS UNDER DIFFERENT LAND UNITS IN GIRISA SUBWATERSHED, IN DUGDA DISTRICT, EAST SHOA ZONE OF OROMIA REGION, ETHIOPIA

Abstract

The decline in soil productivity and crop production are major challenge to ensure agricultural sustainability and food security in East Africa sub-Saharan country like Ethiopia particularly in the study area at Girisa SubWatershed of Dugda District. In order to alleviate this integrated soil fertility management has crucial role. However, there is no or very limited information and documented data on assessment of soil fertility status in Girisa SubWatershed, in Dugda District. Therefore, this study was conducted at Girisa Watershed in Dugda District of East Shoa Zone Oromia Region, with the objective to characterize selected physicochemical properties of soil and to assess soil fertility status. Based on the dominance of land use types they had in the watershed, soil management practices and to a lesser extent the slope gradient, the study area was divided into 6 land units (LUs). Following this, a total of 24 composite soil samples were collected from the surface depth of 0-20cm during 2019 off-season after crops harvested and taken to laboratory. Data were analyzed using GenStat version 15. Accordingly, most of the analyzed physical properties of soil affected significantly (P<0.05) by land units while all the analyzed chemical properties were significantly (P<0.01) affected by land units. Bulk density was within an acceptable range between 1.30-1.60 g cm-3. Lowest and highest mean values of total porosity were (48.36%) and (50.46%) for land units 3 and 6 respectively and was very high. Soil PH was slightly acid to moderately alkaline. Organic matter content of the soil was very low (< 0.86 %) in most land units. Total nitrogen content in the study area was low (0.05-0.12) in most land units and moderate only in land units 2 and 6. The C: N ratio was found to be very low ((<8) in the study area. Available P was in medium (10-17) level. Exchangeable Mg was found in the range of high (3-8 Cmol (+)/kg soil) in the study area while exchangeable Ca (>20 Cmol (+)/kg soil) and K (>1.2 Cmol (+)/kg soil) were very high in the area and exchangeable Na was low (0.1-0.3 Cmol (+)/kg soil) in most land units. CEC was high (25-40 Cmol (+)/kg soil) while PBS was very high (>80 Cmol (+)/kg soil) in most land units. The area had adequate extractable Fe, Mn and Zn while there was deficiency of Cu. It can be concluded that this may be baseline information for soil fertility status and can support decision makers, management planners and for further study and integrated soil fertility management and crop rotations of cereal-legume based should be applied. Furthermore soil characterization and agronomic practices that are best suited for the area should be recommended.