Coffees with specific taste and quality fetch higher prices. Although coffee plays a dominant role in the Ethiopian national economy, the country's coffee industry is generally characterized by low productivity and low quality. To address this issue, this study analysed the interactive effect of shade and nitrogen supply, fruit thinning and genotype by environment interactions on different coffee quality attributes. Organoleptic bean quality attributes declined with increase in radiation when nitrogen supply was limiting. In the absence of nitrogen limitation, however, the quality attributes hardly responded to radiation levels. In full sun, nitrogen had no effect on size and weight of coffee beans. Nitrogen supply improved bean size and weight at lower radiation levels. Fruit thinning and higher altitude significantly improved beverage quality, size and weight of coffee beans. Thinning beyond 50%, however, did not further improve the quality attributes. Effects of shade, nitrogen, fruit load and altitude are consistent with the proposition that organoleptic quality and the size of coffee beans are promoted by factors and conditions that support non-limiting supply of resources for beans to grow and by a sufficiently long period of maturation. Quality attributes did not differ much between varieties suggesting that crop management and growing environments may be more important determinants of quality than the genetic factors.

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In-depth forest coffee cup quality assessments have not been conducted yet on Kafa Biosphere Reserve coffees. Hence, the influence of location, elevation gradient, and processing methods on coffee bean physical and sensorial qualities, and the relationship between soil and coffee quality variables were studied in 2017. Districts (Gimbo, Gawata, and Decha), elevation gradient ranges (low-<1600, mid-1600-1800, and high->1800 m a.s.l), and processing methods (wet, semi-wet, and dry) were taken as factors. Preliminary coffee quality assessment data was collected from cup quality analysis of coffee beans obtained from the combination of the three factors where four replicate samples were taken for each of the combinations. The effect of location was only significant for bean moisture content and there was no significant (P > 0.05) difference among locations for above 14 screen retention and preliminary cup quality variables (odor, raw, acidity, body, flavor, cup, total, and grade). The elevation gradient had a significant (P < 0.001) effect on the scores of above 14 screen retention and most of the cup quality variables, but not on moisture content and odor. The effect of the coffee processing method was not significant (P > 0.05) on most of the preliminary cup quality variables, but it was significant for moisture content (P < 0.001), odor (P < 0.05), and overall raw (P < 0.01) scores. Screen retention was decreased with increasing elevation gradient but with better quality. High elevation coffees processed with the dry method gave better raw (38.5–40 ​%) and cup (48.00–51.75 ​%) quality scores. Except for high soil molybdenum and clay percentage, reduced amounts of most of the soil nutrients, pH, and silt percentage were important for better forest coffee quality. Since each sampled forest had diverse shade types and densities, a further investigation that includes the component of shade is strongly recommended in future studies.