UBC Theses and Dissertations
Analysis of the sustainability and management of the talun-kebun system of West Java, Indonesia Christanty, Linda
Bamboo talun-kebun is one of the traditional agroforestry systems in West Java, Indonesia, in which annual food crops are alternated with a fallow period of bamboo and trees. Its overall pattern is similar to that of traditional shifting cultivation, but the length of the fallow period is much shorter and there is a deliberate selection of species planted in each stage. Because of increasing population pressure, easier access to fertilizer and pesticides, and aspirations for a higher standard of living, some farmers are intensifying the cropping, shortening the fallow stage, or replacing the bamboo with other cash crops. These changes raise concerns about the maintenance of site productivity. This study was undertaken to analyze the sustainability of the bamboo talun-kebun under the current management practice by examining the biogeochemistry of five major nutrients (N, P, K, Ca, and Mg) in various stages of the cycle, and by using this information to assess the effects of extending the period of cropping on production. The energy efficiency and some other aspects of the talun-kebun management practice were also examined. Plant biomass and the accumulation and distribution of nutrients (N, P, K, Ca, and Mg) in plants and in mineral soils were determined over a complete bamboo talun-kebun rotation cycle to provide the data needed for the biogeochemical analysis. The dynamics of litterfall, forest floor, and soil organic matter mass and nutrients were studied. The inputs and outputs of nutrients to and from the system in precipitation, soil leaching, fertilizer, biological fixation, and losses in the burning of forest floor and slash were measured and/or estimated. Approximately 96.5 t ha⁻¹ of biomass was accumulated and 62.8 t ha⁻¹ were removed from the site over a six year talun-kebun rotation cycle. Biomass removals during the first and second year cropping of food species accounted for 17 and 11% of the total removals, respectively. The overall removals represented the loss of 53% of N, 43% of P, 43% of K, 46% of Ca, and 42% of Mg accumulated in the live plant biomass over the rotation cycle. An input-output balance of nutrients over a complete talun-kebun rotation cycle indicated that harvest removals was the major pathway for nutrient loss from the system. The nutrient budget analysis of the cycle indicated the importance of the fallow stage to the long-term sustainability of the system. Nutrients were accumulated in the forest floor and in plant biomass, while minor losses from the system occurred only through leaching. Therefore, shortening the fallow stage might lead to a depletion of nutrients in the mineral soil. A tabular analysis to assess the consequences for nitrogen uptake and biomass production of extending the period of mixed cropping and reducing the length of the fallow emphasized the importance of the fallow stage for the maintenance of site productivity. Extending the period of mixed cropping without increasing the use of fertilizer would lead to a depletion of the site nutrients and a decrease in biomass production, which would be followed by a decrease in litter production and in turn would reduce the amount of nutrients returned to the soil. Although sale of the products from the talun-kebun was not the main source of income for the farmers, the costs of production were low (limited to labor cost), and the system was economically profitable. The talun-kebun proved to be an energy efficient cropping system. The ratio of net energy output/input of food crop production was 38:1.