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The study was conducted in the natural coffee forest ecosystems of southwest and southeast Ethiopia, where the wild populations of Coffea arabica L. naturally grow. Soil is an important environmental factor that performs different important functions in the terrestrial ecosystems, including in the natural coffee forest ecosystems. The objective of this study was to investigate the link between soil properties and bean quality of wild Arabica coffee in the natural coffee forests of Ethiopia. Data on soil parameters and bean characteristics were assessed. Results from simple correlation analysis, stepwise regression analysis and ordination analysis (principal component analysis - PCA, redundancy analysis - RDA) showed that bean size distribution of wild Arabica coffee was clearly related to the soil characteristics of the natural coffee forest ecosystem. Monte Carlo permutation test for the first RDA axis was significant (p=0.0020) with 499 permutations. Forward selection procedure showed that soil pH, Mn, sand, Na, available P and organic matter (OM) significantly contributed to the variability in bean size distribution of wild Arabica coffee. Soil parameters such as soil pH, Mn, pH, CEC, OM, total N, Ca, Na and pH relatively favoured the development of larger beans, whereas higher available P, K and silt contributed to the development of smaller beans. Moreover, the first RDA axis clearly discriminated coffee samples of the southeast coffee forests from those of the southwest coffee forests, and the variation in bean characteristics clearly followed the trend of soil characteristics. Thus, soil is an important environmental factor for the physical quality of wild Arabica coffee.