De heer Mai Van Trinh, MSc : "Soil erosion and nitrogen leaching in Northern Vietnam: Experimentation and modelling"

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17 apr 2007 13:30
Onderdeel: Wageningen Universiteit
Locatie: Aula, gebouw 362, Gen. Foulkesweg 1, Wageningen
Organisatie: Wageningen Universiteit
Co-Promotor: Prof.dr.ir. H. van Keulen (Promotor), Dr. R. Roetter, Dr. R. Hessel

 Two years research has been conducted in Tam Duong district, northern Vietnam. Degraded soil was delineated using satellite images with the largest area of 3280 ha in 1992, associated with substantial reduction in forest cover and agricultural practice. In the mountainous and hilly areas, soil erosion is the dominant process, very severe at plot scale but far less at (sub-) watershed scales. Soil erosion model LISEM showed underestimated simulated runoff and soil loss in main watershed but overestimated simulated soil loss in sub-watershed. In terraces, simulated results from a nitrogen balance model showed increase nitrogen leaching with increasing fertilizer doses. In flat lowland, annual leaching losses were calculated of up to 193 kg ha-1 yr-1 in flowers and 115 in vegetable compared to 50 in rice. A spatial dynamic model was developed to simulate nitrogen dynamics at sub-regional scale. Simulated results showed high leaching losses in flowers (88 to 122 kg N ha-1) and vegetable (51 to 82) compared to 36 to 55 in rice. The study indicated a serious threat for the quality of the natural resource (soil and water) of current agriculture in the district. The conflicts between the various objectives, involving various stakeholders, need to be addressed through integrated analysis.
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