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Please use this identifier to cite or link to this item: http://hdl.handle.net/123456789/2667

Title: MODELING SOIL NITROGEN BALANCE USING GEOGRAPHICAL INFORMATION SYSTEMS AND REMOTE SENSING: THE CASE OF LOWER BILATE RIVER BASIN, SOUTHERN ETHIOPIA
Authors: Andualem, Aklilu
Advisors: Dagnachew Legesse (PhD)
Keywords: GIS/RS, Inflow
Outflows, Soil Nitrogen Balance
Plant Available Stock Soil Nitrogen
Lower Bilate River Basin
Copyright: Jun-2009
Date Added: 6-May-2012
Publisher: AAU
Abstract: The consideration of soil fertility decline primarily referred to the exploitation of soil nitrogen. Nitrogen could be added to the soil via Commercial fertilizers, Organic inputs, Biological nitrogen fixation and Deposition. Conversely, it may be lost from the soil through Leaching, Erosion, Denitirification, Crop yield harvest and Crop residue removal. The study area was located in lower Bilate River basin within the Ethiopian rift valley which was characterized by an arid climatic condition with an erratic and unreliable rainfall characteristic. The core objectives of this research were modeling of the soil nitrogen balance and the plant available stock soil nitrogen by using a spatially explicit methodology of Remote Sensing and Geographical Information Systems. Moreover, the uncertainties and source of errors were assessed. To accomplish the mentioned objectives the study had integrated various primary and secondary data from various sources. The main inputs were digital soil map, Landsat-ETM+ satellite imagery, SRTM data, Rainfall data, and Agricultural data. The basic methodology of Stoorvogel and Smaling (1990) was adapted for soil nutrient balance estimation while the plant available stock soil nitrogen was determined using simple empirical relations. The research found out that in general croplands are endowed with lower amount of plant available stock soil nitrogen than non croplands. The addition of Commercial fertilizers like DAP and Urea were the main inflows in maize land while the fertilizer NPK was the major source of inflow in tobacco farm. Animal manure was the main source of nitrogen inflow in lands of Sweet potato, Cotton and Bush and Scattered shrub land. Harvested crop yield was the major source of nitrogen loss in crop lands. The removal of crop residues was the second most important source of nitrogen outflow in the area followed by Denitirification and Erosion. The soil nitrogen balance modeling revealed that 6 % of the area was very strongly depleted (> 40 N), 31 % was strongly depleted (20-40 N), and 61 % was slightly depleted (< 20 N). Flows such as Commercial fertilizer, Harvested yield and Residue removal were the possible sources of errors in the final soil nitrogen balance estimation. Land and water management technologies which maximize inflows of nitrogen while reducing the outflows like addition of Commercial and Organic fertilizers as well as soil and water conservation structures were the possible remedial measures that could alleviate soil fertility decline problem in the area
URI: http://hdl.handle.net/123456789/2667
Appears in:Thesis - Earth Sciences

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