Agricultural production in the East African Highlands mostly
relies on small-scale farming, which is characterized by labourintensive
agriculture with low inputs and low outputs. Coffee
(Coffea arabica L.) is a major cash crop in these regions. It serves as a
main source of income for small-scale farmers and strongly
contributes to the national export revenues. In addition, banana
production (Musa spp. AAA) serves as a staple or a secondary cash
crop (Wairegi and van Asten, 2011). Demand for agricultural
outputs increases due to population growth and causes pressure
on the available land, leading to decreasing soil fertility (Drechsel
et al., 2001).