Factors Affecting the Salinity Intrusion at the Paddy Field in Thua Thien Hue Province, Vietnam.

Background: Several coastal regions in Vietnam have been suffered from salinity intrusion as a consequence of global climate change. However, there are limited studies on saline intrusion in Vietnam. This paper aimed to investigate the salinity intrusion of water and soil samples in paddy fields along Tam Giang lagoon, Thua Thien Hue province and clarify the factors affecting the salinity level. Methods: We measured the salinity concentrations (EC, Electrical conductivity) of water and soil samples in paddy fields at different distances (400, 600, 800, 1000 and 1200 m) from Tam Giang lagoon. The multiple regression analysis was performed to figure out the factors affecting the salinity concentrations. Result: The salinity concentrations of water were assessed as 48% high saline (10-25 dS m-1), 34% moderately saline (2-10 dS m-1), 2% slightly saline (0.7-2 dS m-1) and 15% non-saline (<0.7 dS m-1). As for surface soil in paddy field, 14.3% moderately saline (4-8 dS m-1), 35.4% slightly saline (2-4 dS m-1) and 50.3% non-saline (0-2 dS m-1) were measured. A significantly positive correlation was found between salinity concentrations of water and soil (n=175, r=0.886, p<0.01). The distances from salinity sources, Tam Giang lagoon and shrimp pond, were major factors affecting the salinity concentrations. The paddy fields near Tam Giang lagoon and shrimp pond have higher salinity concentrations compared to those areas close to the residential area. The surface water in the paddy field within 1000 m from the salinity source was assessed as saline that might harm the paddy soil and rice production. The results of this study provide highly useful information for local policymakers and farmers about the status of salinity intrusion in paddy land. [ABSTRACT FROM AUTHOR]