Soils Acidity Characterization, Mapping and Lime Recommendation of Jimma Arjo District, East Wollega Zone of Oromia Region, Ethiopia

Abstract Background: Soil fertility is one of the major constraints of agricultural production and productivity. Soil fertility atlas shows plant nutrient status and is useful for decision making in fertilizers and other amendments advisory service for farmers. The objectives of this research were to study the farming activity, assess the acidity status of the soils, map and recommend the right amount of lime for acidic soils. Result: A total of 199 soil samples were collected across Jimma Arjo district at 1.5 km grid interval from a depth of 0 - 20 cm for annual and 0 - 50 cm for perennial crops. The total area of the district was 76,574 ha. Soil reaction (pH), electrical conductivity (EC) and exchangeable acidity (EA) were done at Nekemte Soil Research Center. Exchangeable bases (Ca, Mg, K, Na) were analyzed by wet chemistry analysis at Yara Analytical Services, England. Critical levels adopted by the Ethiopian Soil Information System (EthioSIS) project were used for characterization of the soil properties. Soil reaction (pH) ranged from 4.45 to 6.87 in which 17.1 and 78.4% of the total area was covered by strongly acidic soils and slightly acidic soils, respectively. Agricultural lime (Ag-lime) was required for 17.87% of the total area and 12.63%, 4.36% and 0.88% of the total area require lime at a rate of 0 - 1, 1 - 2, and 2 - 4.1 tons/ha respectively. Conclusion: The highland areas of the district are more populated and there is high pressure on soil, cooler temperature and higher rainfall than lowlands which resulted in soil acidity of the highlands. The magnitude and extent of soil acidity in the area is expanding and liming is very important as an entry point to mitigate further expansion. The observed dependency of the soil acidity on landscape position could be a proxy indicator of the difference in fertility status of the two landscapes.