2002 Volume 91 Pages 25-38
Sediments transported from various land uses and entrapped by natural vegetative filter were measured from January to November 1999 in a hilly humid tropical area of Lampung, South Sumatra, Indonesia. A very simple sediment trap made from a PVC pipe with diameter of 10.9 cm was designed for measuring the sediment yield. Five types of land uses were chosen as follows : (a) coffee garden in multistrata system followed by rain-fed agriculture and grass filter, (b)mixed-coffee garden followed by short shrub filter, (c) clean-weeded coffee garden followed by long shrub filter, (d) clean-weeded coffee garden, and (e) secondary forest followed by new forest remnant. The measurement during eleven months showed that the mixed-coffee garden produced the highest sediment yield (719.7g/m2), and the lowest sediment yield was derived from secondary forest area (0.08g/m2). The sediment yield from clean-weeded coffee system was around 93.4-279.7 g/m2, and multistrata system indicated a low sediment yield (2.3 g/m2). Although mixed-coffee garden showed a very high yield of sediment, natural vegetative strips entrapped 99.7% of the sediment. The vegetative filter zone covered with grass (1.5 m long) and short shrubs (3 m in length) could entrap 93.5% and 99.7% of sediment respectively, and the long shrub filter (12 m in length) could entrap only 52.5% of the sediment due to the concentrated flow in the longer slope. The surface cover condition of the land use system and farming activities (weeding, tillage, fertilizer application) indicated a high contribution on sediment yield than the other erosion factor.
