Altitude, shading, and management intensity effect on Arabica coffee yields in Aceh, Indonesia

The productivity of Arabica coffee in the Gayo Highlands, Aceh, Indonesia is far below its potential because of climate change and inadequate agricultural practices. To develop a strategy on sustainable coffee yield and improvements of smallholder farming systems, we investigated coffee productivity in three classes of shade densities and three classes of total management intensities index (TMI) along six altitude gradients (1,000-1,600m above sea level) over 234 farmers' plots. Coffee productivity was significantly affected by altitude, shade density, and TMI. Our results showed a stronger positive altitudinal effect with coffee productivity in middle and higher altitudes than in lower altitudes and were related to shade density and TMI. Increasing elevation of coffee plantation from lower to middle altitudes and shade from low to medium density increased in coffee productivity but further increase to higher altitude seemed to depress coffee productivity. Increasing TMI positively increased coffee productivity across altitudes. Shade density and TMI played significant roles in coffee productivity in lower altitudes; therefore, coffee farmers have to increase the shade to medium or higher density and at the same time improve plantation management to medium or high TMI.