Productivity Improvement of Smallholder Coffee Plantation to Prevent the Expansion of the Plantation into Protected Forest

Abstract

Farmers expanded the smallholder plantation to the protected tropical rainforest area due to declining of coffee productivity by the old age of coffee trees and degraded soils in West Lampung, Sumatra Island of Indonesia. The research aimed to study the performance of rehabilitated Robusta coffee trees and citronella grass (Andropogon nardus L.) as a conservation crop to improve the smallholder coffee plantation productivity. The old Robusta coffee trees (more than 25 years old) were rehabilitated by side grafting. Scions for the grafting were superior clones such as Sumber Asin (SA) 237, Besoekish Proefstation (BP) 436, and 534. In the experiment, two scions were grafted to each of 600 local Robusta coffee trees. To know the effect of grafting, the coffee trees were observed using stratified random sampling with equal sample allocation. The strata were varying positions of land on the hill, i.e., peak, ridge, and bottom, and the other were the three clones. The citronella was planted along the contour line among the coffee trees, with a vertical interval (VI) was 1.25 m. On average, the two grafted branches of coffee trees could produce green beans 453 g. It was higher than the average yield of the farmers’ coffee trees, i.e., 387 g tree-1. The SA 237, however, was vulnerable to the attack of berry borer (Hypothenemus hampei). Besides, to control erosion, the citronella grass under 40 to 60% covered by coffee trees canopy, produced fresh leaves 10-ton ha-1year-1 or essential oil as much as 87 L (essential oil content of leaves 0.87%), approximately. That was equivalent to $1,115 in a year. The citronella also improved the soil chemical properties, especially organic-C, P2O5, Ca2+, Mg2+, and Al3+.