In southern Sumatra, many coffee farms exist as row after row of coffee plants.
These are robusta coffee plants (as opposed to Arabica), grown on a hillside of bare dirt with few shade trees.
Coffee cultivated in this manner requires a great deal of effort to maintain by the farmer.
A virtual monoculture (single species of crop), the system has few natural insect predators.
Therefore, pesticides and herbicides must be applied to control pests and weeds that might otherwise be kept in check by the more diverse insect community that is associated with an agroforestry setting.
Moreover, fertilizer is necessary as the soil and its nutrients wash away in torrential rains.