In Vietnam, wetlands have generally been perceived as wastelands. Large wetland areas were altered for agriculture, especially in the Mekong Delta, where rice production is a top priority for national food security and export Drainage of wetlands for agriculture has resulted in severe acid water pollution and degradation of wetland ecosystems where a native species Melaleuca cajuputi once dominated. The native Melaleuca forest provides many values for both people and environment. Rehabilitation of the Melaleuca forest faces policy conflicts for development programmes, immediate problems of poverty and lack of appropriate technical information. Poverty affects 15-20% of the population of the Delta, with many people landless and exploiting natural resources for their main income. This study examines the scientific basis for integration of the environmental and socioeconomic functions of Melaleuca into farming systems and trials a model to achieve this end. The effects of the Melaleuca ecosystem on surface water quality have been identified. Where rainwater passing through the Melaleuca canopy is temporarily acidified, the effect is greater on contact with the trunk than the leaves. Annually, Melaleuca adds 7-12 ton/ha litter to the ground. Litter decomposition led to a pH increase, and a reduction in Fe, Al, and SO4 concentration in surface water. Soil layers contribute to a pH increase under submerged conditions by reducing H' concentration, and soil micro-organisms decreased Fe concentration in acid water. Living Melaleuca and Eleocharis undergrowth significantly reduced Al and S04. concentration in acid water. These experimental results justified the establishment of an agro-forestry trial where Melaleuca forest was integrated with rice cultivation at a farm scale. In this trial Melaleuca land acts as a reservoir to keep flood water to irrigate the rice land, and improves quality of acidic drainage water from the rice land for irrigation. Farmers participated for the duration of three rice crops. The new combination of Melaleuca and rice crop management was linked with the indigenous knowledge of local people in its implementation. This has lead to the trial being readily adapted to field conditions. Specifically, one hectare of Melaleuca land can hold enough water to irrigate 1.5 hectares of rice land, whilst it can improve acidic water drained from 3 hectares of rice land. Farmers have no difficulty in the planting of Melaleuca, but they need information relating to rice crop management Melaleuca plantation provides more profit than the rice crop. The farmer needs to invest only once at the time of crop planting and can harvest after seven to eight years. They can also manage up to 70% of the crop profit at the harvesting time in terms of their own labour. For rice production, the farmer needs to invest in every crop over three to four months, and in terms of their own labour, they can manage only 30% of the crop profit, which is strongly dependent on the market. Thus, integrated agro-forestry based on the combination of Melaleuca forest with rice allows farmers to balance between short-term and long-term income while improving also environmental quality and biodiversity conservation
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:367582 |
| Date | January 2001 |
| Creators | Ni, Duong Van |
| Publisher | Royal Holloway, University of London |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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