Evapotranspiration (ET), which is an elusive component of the hydrological cycle, comprises transpiration from plants (T) and evaporation from soil surface (E). In this regard, it is essential to know how much water is lost by T and E during the irrigation period. The overall aim of this study is to separate the ET components by stable oxygen isotopes of winter wheat at the field scale under different irrigation regimes. For this purpose, the field experiment was conducted under rain-fed, deficit and full irrigation conditions. Soil–water–plant samples were taken for isotopic (¹⁸O/¹⁶O) analyses. According to the research results, a significant positive relationship was found between applied irrigation water and the average T/ET ratio with a correlation coefficient of 0.81. The T/ET ratios were, on average, 70, 75 and 84% for rain-fed, deficit and full irrigation treatments, respectively. During the growing season, 231 and 78 mm of irrigation water were applied for full and deficit irrigation, respectively. This showed that water savings of 66% were achieved, although there was a slight (12%) change in transpiration in deficit irrigation. Also, in the use of the oxygen isotope content results indicated that T was the dominant source of total evapotranspiration.

中文翻译：

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不同灌溉条件下基于氧同位素方法的冬小麦蒸散分配

蒸散 (ET) 是水文循环中难以捉摸的组成部分，包括植物的蒸腾 ( T ) 和土壤表面的蒸发 ( E )。在这方面，必须知道在灌溉期间T和E损失了多少水。本研究的总体目的是通过不同灌溉制度下冬小麦的稳定氧同位素在田间尺度上分离 ET 组分。为此，田间试验在雨养、缺水和全灌溉条件下进行。取土壤-水-植物样品进行同位素 ( ¹⁸ O/ ¹⁶O) 分析。研究结果表明，灌溉用水量与平均T /ET比呈显着正相关，相关系数为0.81。雨养、亏灌和全灌处理的T /ET 比率平均分别为 70%、75% 和 84%。在生长季节，灌溉用水量分别为 231 毫米和 78 毫米，用于全灌和亏灌。这表明节水达到了 66%，尽管在亏缺灌溉中蒸腾发生了轻微的变化（12%）。此外，在使用氧同位素含量的结果表明，T是总蒸散量的主要来源。