The influence of shade tree species and coffee varieties on selected soil physicochemical properties in coffee-based farming system of southwestern Ethiopia

Different shade tree species are used in various coffee production systems across the world. Outside the benefits of biodiversity protection, temperature protection, and carbon sequestration shade trees can influence soil nutrient states through litter inputs and nitrogen fixation. However, little information is available in coffee plantations whether shade tree species and type of coffee variety planted under shade tree have an influence on soil physical properties and nutrient status in coffee-based farming systems of southwestern Ethiopia. Hence, the study was carried out to investigate the effect of shade tree species and coffee varieties in coffee plantation on the physicochemical properties of the soil. The study was conducted in Chora Botor district (Chalalaki coffee plantation), located in Jimma Zone, Oromia regional states of Ethiopia. The study was superimposed on coffee farm that has been established using four released coffee varieties (7440,744, F59 and 75227) under three recommended coffee shade trees (Albizia gummifera, Millettia feruginea and Acacia abyssinica). Soil physical properties and nutrient status were investigated in response to shade tree species, coffee varieties and their combination. The results indicated that the physical and chemical properties of the soil vary across the shade trees and coffee variety grown. The effect of shade tree species on soil depends on the type of coffee varieties grown under the shade tree species, Albizia gummifera and Acacia abyssinica trees enhanced more soil nutrient content and water-holding capacity of the soil than Millttia ferrugnia. Total nitrogen, organic matter, available phosphorous, exchangeable potassium, Cations Exchange Capacity, and bulk density were higher underneath Albizia gummifera than other coffee shade tree species. On the other hand, moisture content, available P, exchangeable K and CEC were higher beneath Acacia abyssinica than other coffee shade tree species. Soil pH was negatively correlated with Millettia ferruginia. Use of Acacia abysinica and Albizia gummifera shade tree species with compatible coffee varieties could be a viable option to augment soil fertility management practices in the coffee production systems of the southwest Ethiopia.