Abegaz (PhD), AssefaNegash, Dugassa2019-12-092023-11-192019-12-092023-11-192019-09http://etd.aau.edu.et/handle/12345678/20321This study tries to assess household energy and soil nutrients with particular emphasis on implications for crop production, household finances and greenhouse gas emissions in the Central Highlands of Ethiopia. Household survey, focus group discussions, key informant interviews, observations and measurements were used for data collection. Kitchen Performance Test and Controlled Cooking Test were applied for assessing stove efficiency. On-farm trials were established to evaluate effects of fertilizers on soil and yield. Descriptive statistics, a paired sample t-test, one way ANOVA, correlation coefficients and linear regression were employed for statistical analysis. Microsoft excels and SPSS version20 were used for data presentation and analysis. Crop residues and dung cakes accounted for 80(±3) % by energy content and 85(±4) % by dry mass weight of total biomass fuel consumption. Mean per household nutrient losses were 109(±8) kg yr-1nitrogen, 26(±2) kg yr-1 phosphorus, (150(±11) kg yr-1 potassium and 3000(±300) kg yr-1 organic carbon. Rich farmers lost significantly more carbon and nutrients in fuel than farmers in other wealth groups. However, these losses were spread over a larger area, so losses per land area were significantly higher for medium and poor than for rich farmers. This means that the land of poorer farmers is likely to become degraded more rapidly due to fuel limitations than that of rich farmers, so increasing the poverty gap. The estimated financial loss per household due to not using dung and crop residues as organic fertilizer was 162(±8) US$ yr-1. However, this is less than their value as fuels, which was 490(±20) US$ yr-1. Therefore, farmers will only be persuaded to use these valuable assets as soil improvers if an alternative, cheaper fuel source can be found. Substitution of a three-stone open fires with improved stoves resulted in significant improvement of fuel use efficiency (p<0.01) with the highest saving in biomass fuel achieved by the mirt stove together with biogas (53.6%) and lowest by the mud-stove without biogas(32.1%) and respective reduction in greenhouse gases emissions were 4534 (±32) kg CO2e yr-1 and 7661 (±43) kg CO2e yr-1; and financial savings from fuel were 471(±2.6) US$ yr-1 & 279(±4) US$ yr-1 per household. Soil texture of the trial fields were suitable for cereals (clay to clay loam) but high to very high in bulk density implying the existence of soil compaction problem. The trial fields were characterized by very low to low total nitrogen, available phosphorus, organic carbon while the C: N ratios, cation exchange capacity and base saturation were within the optimum ranges. The soil pH at Doliyo was strongly acidic (5.10) whereas that of Kumbursa was nearly neutral (6.89). The post-treatment soil test data revealed that application of bioslurry and bioslurry compost individually as well as in combination with inorganic fertilizer tended improve the soil bulk densities and chemical properties with relatively better performance in nutrient uptake. Both total above ground biomass and grain yields linearly increased with increased application rates of nitrogen & phosphorus for all of the treatments with the highest and lowest responses respectively obtained from bioslurry compost combined with inorganic fertilizer and bioslurry only. Wide scale dissemination of improved cookstoves combined with biogas technology is recommended for enhancing availability of organic fertilizer. Integrated application of organic and inorganic fertilizer should be encouraged for maintaining soil fertility and improving crop yield. Finally, further experimentation is required on application rates of different fertilizer types on different soil types in different agroecologies. Key words: Ethiopian Highlands, biomass fuel, household energy, crop residues, dung cakes, cookstove, soil nutrients, agronomic response, nutrient use efficiency, apparent nutrient recoveryen-USEthiopian Highlands, biomass fuel, household energy, crop residues, dung cakes, cookstove, soil nutrients, agronomic response, nutrient use efficiency, apparent nutrient recoveryThesis