Title : Impact of high-dike on rice and wild fish yields, water quality, and use of fertilizers in the Mekong Delta, Vietnam
Abstract:
During the last two decades, numerous high-dike systems have been built in the Mekong Delta, including the An Giang province in the upper floodplains, to protect triple rice cultivation, support other upland crops, and commercial aquaculture production. The development of high-dikes has sometimes increased rice yields per year, farmers' incomes and national export, but it has also negatively impacted water and soil quality, biodiversity, and natural ecosystem’s health, causing a decline in wild fish and other aquatic species. In this research, rice farmers and key stakeholders were asked about the impacts of high-dikes on rice productivity, aquatic biodiversity, water quality, and the use of synthetic fertilizer/pesticide. The studied areas included Cho Moi, Phu Tan, and Chau Phu districts of An Giang province as 97.6%, 93.7%, and 69.1%, respectively, of their agricultural land is covered by high-dikes. The majority of the respondents from three districts perceived that the inflow of nutrient-rich water and sediments, use of synthetic fertilizers, water quality and yield of wild fish and other aquatic animals had changed significantly after the constructing of high-dikes. The high-dykes had increased rice yields with 15.0–48.0%, and the use of synthetic fertilizers with 26.0–36.7%. The water quality was percieved to have decreased from good (ranked as 4 out of 5) to poor (2 out of 5) after the high-dikes had been built. The wild fish yield and fish diversity were estimated to have decreased with 68–83% (P = 0.017) and 75–81%, respectively (P < 0.05), and had decreased most in the Cho Moi district, followed by the Phu Tan and Chau Phu districts. It is concluded that large areas of high-dikes construction with three rice crops receive less nutrient rich water and sediments, and have a more frequent use of chemical fertilizers, which are seen to decrease water and soil quality, aquatic biodiversity, and wild fish yields. that provide important sources of essential protein to people in the region.
