Institute of Crop Science and Resource Conservation (INRES), Soil Science and Soil Ecology, University Bonn, Nussallee 13, 53115 Bonn, Germany; Institute for Bio- and Geosciences - IBG-3, Agrosphere, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany.
Institute for Bio- and Geosciences - IBG-3, Agrosphere, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany.
Sci Total Environ. 2020 Feb 10;703:134758. doi: 10.1016/j.scitotenv.2019.134758. Epub 2019 Nov 4.
Saline water intrusion has become a severe threat in the coastal areas of Mekong delta of Vietnam, though offering farmers the option to diversify their land use, and switching, for instance, from permanent rice to alternating rice-shrimp systems or even to permanent shrimp systems. The objective of this study was to evaluate the respective impacts on soil salinity, nutrient status and their binding forms. Hence, we sampled the topsoils (cultivation layer, 0-15 cm) from 10 permanent rice systems and the rice platforms of 10 alternating riceshrimp systems. Furthermore, the sludges and the soils 10 cm underneath of the sludges from the ditches of the alternating rice-shrimp as well as from ponds of the permanent shrimp systems were sampled in Bến Tre and Sóc Trăng provinces, Vietnam, respectively. The samples were analyzed regarding their electric conductivity, total and plant-available nutrient contents. To reveal possible changes in nutrient binding forms, sequential P and S extraction, 31P-nuclear magnetic resonance spectroscopy, and S and P X-ray absorption near edge structure spectroscopy were applied. The results showed that permanent and alternating shrimp cultivation lead to elevated salt concentrations but also improved the overall nutrient status relative to the permanent rice management and especially in the sludges relative to the soils underneath. The continued deposition of shrimp and feed debris promoted the accrual of stable, Ca- and Mg-associated P forms as well as of P-monoesters, whereas the S forms were depleted in thiophene S groups but enriched in sulfides relative to permanent rice fields. As effects by alternating rice-shrimp management were intermediate, this management has more potential to serve as a no-regret strategy for farmers to remain flexible in their response to climate changes and concurrent salinity intrusion relative to permanent shrimp production, which requires strict maintenance of adequate salinity levels also during the rainy season.
海水入侵已成为越南湄公河三角洲沿海地区的严重威胁，尽管为农民提供了土地利用多样化的选择，例如从永久性水稻转为稻虾轮作系统，甚至永久性虾养殖系统。本研究的目的是评估其对土壤盐分、养分状况及其结合形态的各自影响。因此，我们从 10 个永久性水稻系统和 10 个稻虾轮作系统的水稻平台采集了表层土壤（耕作层，0-15cm）。此外，在越南的薄寮省和朔庄省，我们分别从稻虾轮作的沟渠和永久性虾养殖池塘的底泥及其下方 10cm 的土壤中采集了底泥样本。对这些样本进行了电导率、总养分和植物有效养分含量的分析。为了揭示养分结合形态的可能变化，我们应用了顺序磷和硫提取、31P 核磁共振波谱和 S 和 P X 射线吸收近边结构光谱。结果表明，永久性和稻虾轮作养殖导致盐分浓度升高，但与永久性水稻管理相比，整体养分状况得到改善，尤其是在底泥中相对于其下方的土壤。虾和饲料残渣的持续沉积促进了稳定的、与 Ca 和 Mg 结合的磷形态以及磷单酯的积累，而硫形态中噻吩 S 基团减少，但与永久性稻田相比，硫形态中硫化物增加。由于稻虾轮作管理的影响介于两者之间，因此这种管理策略更有潜力成为农民的一种无遗憾策略，使他们在应对气候变化和海水入侵时保持灵活性，而永久性虾养殖则需要在雨季也严格维持足够的盐度水平。
