Browsing by Subject "Salinity stress"

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    Evaluating topsoil salinity via geophysical methods in rice production systems in the Vietnam Mekong Delta
    (2023) Nguyen, Van Hong; Germer, Jörn; Asch, Folkard
    The Vietnam Mekong Delta (VMD) is threatened by increasing saltwater intrusion due to diminishing freshwater availability, land subsidence, and climate change induced sea level rise. Through irrigation, saltwater can accumulate in the rice fields and decrease rice production. The study aims at evaluating topsoil salinity and examining a potential link between topsoil salinity and rice production systems in a case study in the Tra Vinh province of the VMD. For this, we applied two geophysical methods, namely, 3D electrical resistivity tomography (ARES II) and electromagnetic induction (EM38‐MK2). 3D ARES II measurements with different electrode spacings were compared with EM38‐MK2 topsoil measurements to evaluate their respective potential for monitoring topsoil salinity on an agricultural scale and the relationship between land‐use types and topsoil salinity. Results show that EM38‐MK2 is a rapid and powerful tool for obtaining high‐resolution topsoil salinity maps for rice fields. With ARES II data, 3D maps up to 40 m depth can be created, but compared with EM38‐MK2 topsoil maps, topsoil salinity was underestimated due to limitations in resolution. Salt contamination of above 300 mS m−1 was found in some double‐cropped rice fields, whereas in triple‐cropped rice fields salinity was below 200 mS m−1. Results clearly show a relation between topsoil salinity and proximity to the saline water sources; however, a clear link between rice production and topsoil salinity could not be established. The study proved that geophysical methods are useful tools for assessing and monitoring topsoil salinity at agricultural fields scale in the VMD.
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    Saving the Vietnamese Mekong River Delta - People's attitudes, opinions and willingness to help
    (2023) Ahlheim, Michael; Vuong, Duy Thanh
    The unique nature and environment of the Vietnamese Mekong Delta as well as its agricultural production and its traditional lifestyle are endangered by a rising sea level and increasing salinization of the ground and surface water. This paper aims at the assessment of Vietnamese people's information on and attitudes towards these problems as well as their respective convictions and beliefs. Imbedded in an online survey with 2000 completed interviews we also conducted a Contingent Valuation study with which we want to assess people's willingness to contribute personally and financially to saving the Mekong Delta as an indication of the benefits they would expect from such a project. We interviewed three different groups of respondents, one of which lives directly in the Mekong Delta, a second lives outside the Delta, but close to it, that is in Ho Chi Minh City, and the third group lives far away from the Delta in Hanoi. With these three subsamples of respondents we wanted to capture not only the use benefits but also the nonuse benefits accruing from such a project. In the course of the interviews, we found that the Mekong Delta is of great interest and importance to all interviewees, no matter in which part of Vietnam they live. They were mostly well informed on the problems there and had strong opinions on the causes of these problems as well as on suitable strategies to fight them. In our Contingent Valuation study, we assessed the willingness of people at the different study sites to contribute financially to a hypothetical project for the preservation of the Mekong Delta and the socio‐economic, attitudinal and psychological determinants of this willingness. Besides these empirical findings, we also obtained valuable insights regarding various methodological aspects of Contingent Valuation studies.