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Rubber agroforestry systems-type 3 (RAS3), a strategy to convert Imperata grasslands

Boutin D., Penot E., Ilahang I.. 2001. In : Azwar Rasidin (ed.), Karyudi (ed.), Wibawa Gede (ed.), Suryaningtyas Heru (ed.), Arizal Ridha (ed.), Honggokusumo Suharto (ed.), Suparto Dadang (ed.), Supriadi M. (ed.), Anwar Chairil (ed.), Suwana Ayuni-Dewi (ed.). Indonesian Rubber Conference and IRRDB Symposium 2000, Bogor, Indonesia, 12 - 14 September 2000 : Proceedings. Medan : Indonesian Rubber Research Institute, p. 266-273. IRRDB Symposium, 2000-09-12/2000-09-14, Bogor (Indonésie).

Lalang (Imperata cylindrica) is known to be the most noxious weed in the tropics and a major constraint for food and tree crop development. Estates developed technologies to suppress Imperata using chemical herbicides and promoting the establishment of legume cover crops (LCC). These technologies have been also used in assisted smallholder schemes but such methods are too costly to be widely adopted by farmers in self-help development. In SRAP (Smallholder Rubber Agroforestry Project) a different approach for the suppression of Imperata was tested. The association of various cover crops, shrubs and fast growing trees (FGT) with rubber is used to control Imperata by shading. The system was called "Rubber Agroforestry System-type 3" (RAS 3). All experiments were conducted in smallholders' fields with participatory approach. The association of different species with rubber aims to assess the ability of various plants to control Imperata and to evaluate the impact of the association on rubber growth. Legume shrubs like Flemingia congesta were found effective to control Imperata as the rubber growth in RAS type-3 was found similar to growth with conventional technologies using Pueraria phaseoloides after 3 years of experiment. Fast Growing Trees (FGT) like Acacia mangium, Acacia Crassicarpa, Paraserianthes falcalaria, Gmelina arborea did not affect rubber growth after a period of 42 months. Before experiment establishment, all the plots were infested by Imperata but during trial implementation, flora composition changed and some plots were invaded by Chromolaena odorata and Melastoma affine reducing Imperata extend. Acacia mangium was founded as the most effective tree to suppress Imperata by shading. As Acacia trees become competitive to rubber at the age of 42 months, they must be pruned or felled to prevent a depressive effect on rubber growth due to competition for light. Fast Growing Trees (FGT) associated with rubber can help Imperata control reducing maintenance cost in rubber farms however, the planting pattern of associated trees with rubber must be adapted using wider inter-row if an income from pulpwood sales is expected.
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