We characterized 63 fields sampled based on farmers’ perception of production risks within each commune (referred as either safe or at-risk fields), from the 3 communes in the 2 contrasting estuaries with different farming transformation in Red River Delta, Vietnam (Giao Huong and Giao Thien communes in Ba Lat estuary, Nam Dien communes in Day estuary), for 6 cropping seasons from 2015 to 2017. Rice yield was lower in Nam Dien (472 g/m²) than in Giao Huong (619 g/m²) and Giao Thien (662 g/m²), because of higher salinity levels in Day estuary than in Ba Lat estuary (8.0 ± 4.7 vs 2.9 ± 5.5‰), which led to higher salinity in standing water in the paddies (1.1 ± 0.3 vs 0.8 ± 0.3‰ in spring rice, 0.6 ± 0.3 vs 0.2 ± 0.2‰ in summer rice), and higher [Na⁺] in the surface soil (2.13 vs 1.7 meq/100 g). At-risk fields had higher water salinity and soil Na⁺, higher sand proportion, deeper standing water and lower yield than safe fields (558 vs 649 g/m²). Short duration inbred variety was most sensitive to increasing salinity, and farmers planted more hybrid varieties at at-risk fields in spring. Tall local glutinous cultivars with lower yield potential were planted at at-risk fields in summer with less N fertilizer. N fertilizer application rate was high (ca. 200 kg/ha/season) with low use efficiency. This study highlighted small-scale environmental variation and adaptation and yield reduction due to salinity in the two contrasting estuaries in the Red River Delta.

中文翻译：

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盐分入侵降低了沿海稻田的谷物产量：以越南红河三角洲的两个河口为例

我们根据农民对每个公社内生产风险的感知（称为安全或高风险农田）对63个田地进行了特征分析，这些地区来自越南红河三角洲两个不同农业转型的河口中的三个公社（Giao Huong 2015年至2017年的6个种植季节分别位于Ba Lat河口和Nam Dien镇的Giao Thien镇。Nam Dien（472 g / m ²）的水稻产量低于Giao Huong（619 g / m ^2））和Giao Thien（662 g / m ²），这是因为Day河口的盐度比Ba Lat河口的盐度高（8.0±4.7对2.9±5.5‰），这导致稻田的静水盐度更高（1.1±春稻分别为0.3和0.8±0.3‰，夏稻为0.6±0.3和0.2±0.2‰，甚至更高[Na⁺ ]在表层土壤中（2.13对1.7 meq / 100 g）。与安全田相比，高风险田的水盐度和土壤Na ⁺较高，沙比更高，积水更深，单产也更低（558 vs 649 g / m ²）。近交近交品种对盐分增加最敏感，春季农民在高风险的田地上种植了更多的杂交品种。夏季，在高风险的田地上，使用较少的氮肥，种植高产潜力较低的高糯品种。氮肥施用率高（约200千克/公顷/季节），使用效率低。这项研究强调了红河三角洲两个相反河口中由于盐度引起的小规模环境变化，适应和减产。