Deterioration of soil fertility by land use changes in South Sumatra, Indonesia: from 1970 to 1990
✍ Scribed by Jamalam Lumbanraja; Tamaluddin Syam; Hiroyo Nishide; Ali Kabul Mahi; Muhajir Utomo; Sarno; Makoto Kimura
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 409 KB
- Volume
- 12
- Category
- Article
- ISSN
- 0885-6087
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✦ Synopsis
We monitored the land use changes in a hilly area of West Lampung, South Sumatra, Indonesia, from 1970 to 1990. The main data sources were the land use maps produced in 1970, 1978, 1984 and 1990 covering the area of 27 km  27 km. Transmigration and the resultant eect of increased population were the major driving forces in land use changes. Fifty-seven per cent of the study area was covered with primary forests in 1970, but only 13% in 1990. Areas under plantations, which were absent in 1970, increased to 60% in 1990. In addition, the change from monoculture plantations (mostly coee plantation) to mixed plantations was noticeable from 1984 to 1990. Total upland areas including upland areas under shifting cultivation and upland ®elds with crops and vegetables decreased from 21% in 1970 to 0 . 1% in 1990. Soil chemical properties (total organic C, total N, available P, total P, exchangeable cations, cation exchangeable capacity (CEC), etc.) were analysed for lands under dierent land use forms after deforestation in the study area. Soil samples (surface layers, 0±20 cm, and subsurface layers, 20±40 cm) were collected from three dierent locations, each comprised of four dierent land use systems: i.e. primary forests, secondary forests, coee plantations and cultivated lands. The contents of total organic C, total N, available P, total P, exchangeable cations and CEC decreased signi®cantly with land use change from primary forests to the other land use forms. Cultivated lands exhibited the lowest values. Although less remarkable than in the surface layers, the amounts of total organic C, total N, total P, exchangeable cations and CEC were also decreased by forest clearing in the subsurface layers.
Based on the land use changes from 1978 in the study area and the deterioration of soil chemical properties by forest clearing, total decreases in the amounts of nutrients in the surface and subsurface layers were estimated. The land use changes were estimated to have decreased the total amounts of total organic C, total N, available P, total P, exchangeable cations and CEC by 2±9% in 1984 and by 2±15% in 1990 in the surface layers, and by 1±6%% in 1984 and by 2±9% in 1990 in the subsurface layers from the levels in 1978, respectively.