Soil Acidity Induced Land Use/Management Change, and its Impact on Soil Chemical and Biological Properties in the Central Highlands of Ethiopia

Abstract

Land use/management changes have become more common in the highlands of Ethiopia due to the prevalence of soil acidity, population growth  and their demand for diverse products that might have positive or negative consequences on soil resources. In an attempt to explore the effect of  soil acidity induced land use/management changes on soil properties, remote sensing and evaluation of selected soil chemical and biological  properties in the different land uses was carried out. Analysis of remote sensing data categorized four major land use/cover classes: natural forest,  Eucalyptus plantations, cropland/settlements and grasslands. In 1975, natural forest, Eucalyptus plantations, croplands/settlements and grasslands  occupied 3.5, 7.5, 28.8 and 61.5 % of the total land area, respectively. Over a period of 39 years (1975 to 2014) of analysis, Eucalyptus plantations and  cropland/settlements increased by 335 and 62.5 %, respectively. Soil chemical and biological properties under three land use (grassland,  cropland, Eucalyptus) and two management systems (limed land and fallow land) all existing adjacent to each other were compared. Results of soil  chemical and biological analysis showed considerable differences between the grassland and other land uses and management systems  considered. A reduction of 53, 45, 46 and 47% in soil organic carbon (SOC) was observed under cropland, Eucalyptus, limed and fallow lands,  respectively. However, cropland, Eucalyptus and limed fields showed similar values for most of the soil chemical properties studied. Soil microbial  biomass carbon (MBC) and microbial biomass nitrogen (MBN) were also significantly higher under grassland, and lower under fallow land.  Furthermore, results clearly demonstrated that deterioration in soil chemical properties is more pronounced in 10-year-old Eucalyptus plantations  than in 5-year-old Eucalyptus. Soil organic carbon, the MBC to SOC ratio and MBN to total nitrogen could be considered as the three most important  bio-chemical parameters to assess functional capacities of soils for soil acidity affected areas in the central highlands of Ethiopia.