Biophysical Factors and Agronomic Practices Affected Quality and Biochemical Compositions of Coffea arabica in South and Southwestern Ethiopia

Arabica coffee is grown at higher elevations in Ethiopia and when grown on healthy soils typically yields denser and harder beans that are more highly valued due to their elevated sugar content, resulting in complex and desirable flavors. The biochemical compositions of green coffee beans, including key compositions such as caffeine, trigonelline, and chlorogenic acid, play a vital role in developing coffee’s aroma and flavor, ultimately influencing the quality of the final beverage. However, information on this quality attributes is limited in Ethiopia. Hence, this study was carried out in seven major coffee-producing districts of south and southwestern Ethiopia and investigated the effects of biophysical and agronomic practices on the quality and biochemical compositions of Arabica coffee in the country. Data on physical, sensory, and biochemical compositions of caffeine, trigonelline, and chlorogenic acids were collected, and the data were analyzed by high-performance liquid chromatography (HPLC) at the EIAR, Food Science and Nutrition Laboratory. The results indicated the existence of no significant differences in the mean raw, cup, and total coffee quality scores across altitudes (35.74%, 47.53%, and 83.35%, respectively). Similarly, altitude did not significantly influence the biochemical compositions of coffee beans. However, soil properties vary with altitude, with lower altitudes generally exhibiting higher fertility, which showed a positive correlation with the coffee quality. Regression analysis revealed a very strong positive relationship (R2 = 0.9988) among altitude, soil fertility, and coffee quality attributes. Notably, lower-altitude soils, characterized by an approximately +23% higher organic carbon content, were positively associated with improved cup quality scores (mean = 47.53). These findings highlight that soil fertility status exerts a stronger indirect influence on coffee quality than altitude alone. Based on these results, targeted agronomic interventions are recommended, including the application of organic amendments to enhance soil organic carbon and cation exchange capacity in lowland areas and shade tree optimization to moderate microclimate conditions in highland zones. This study provides valuable evidence for site-specific, soil-based management strategies aimed at improving the quality and sustainability of Ethiopian Arabica coffee production systems.