Erosi dan Aliran Permukaan pada Lahan Pertanian Berbasis Tanaman Kopi di Sumberjaya, Lampung Barat

Abstract

Coffee-based farming has been perceived by policy makers as having a high erosion and a source of sedimentation. Past approach to control erosion and restoring forest function have been by forceful replacement of coffee plant with timber or leguminous tree species such as Calliandra calothirsus, and eviction of the farmers from the forest jurisdiction area. This research was aimed at testing the level of soil loss under different soil conservation treatments on land covered by 3 year old coffee trees. The research was conducted on land with slopes ranging from 50 to 60% at Laksana and Tepus sites of Sumberjaya District, West Lampung province from November 2001 to July 2003. Erosion measurement was conducted at plots 15 m long and 8 m wide. Five treatments in 4 replications in a completely randomized block design included: T1 = Sun coffee (open field monoculture coffee), T2 = T1 + Gliricidia as shade tree, T3 = T2 + dead end trench (rorak), T4 = T2 + hedgerows of natural vegetation, and T5 = T2 + ridging. The results indicated that erosion level on the 3 year old coffee farm with porous soil structure was very low (< 2 Mg ha-1 yr-1) and thus soil conservation treatments had no significant effects on soil loss, run-off, and soil organic matter and nutrient lateral transport. Soil physical properties (especially drainage pore and permeability) are dominant factors that determine the level of soil loss in the study sites. The results of the research proved that, for areas covered by 3 year old or older coffee, with soil structure similar to that of Laksana and Tepus, coffee trees per se are sufficient to control erosion to tolerable level.