The profile of crop water uptake from the soil depends on rainfall regime (amount, seasonality, frequency distribution of rainfall event size), soil, crop, and management. This study, with a focus on winter wheat in a wheat-fallow system, combines measurements of hydrogen (δD) and oxygen (δ18O) isotopes with a Bayesian mixing model (MixSIAR), and measurements of root length density to (i) quantify crop water uptake from soil down to 3 m depth, (ii) to assess the influence of soil water at sowing, soil mulching, seasonal conditions and their interaction on the profiles of soil water uptake, and (iii) to probe for relations between yield and the profiles of soil water uptake. Across treatments and seasons, water uptake at jointing featured a ratio 2.1: 1.0: 1.8: 2.2 in four soil layers, top 0.2 m, 0.20.4 m, 0.41.2 m, and 1.2–3.0 m. At anthesis, the ratios shifted to 5.2: 1.0: 1.7: 2.0. Water uptake at jointing was higher from top-soil in dry (∼60 %) than in wet condition (∼30 %), and the opposite was true in deeper layers; water supply had a smaller effect on the profiles of water uptake at anthesis. Compared to bare ground, mulch favored root proliferation and water uptake in 0.42.0 m soil layer. For a given soil layer, soil moisture correlated negatively with root length density. Yield correlated positively and linearly with water uptake from 0.43.0 m soil at jointing, indicating that faster root development at early stages favors water uptake from deep soil in the critical period of grain yield formation. We discuss the implications of our findings for agronomic management and breeding.

中文翻译：

---

根系、δ18O 和 δ2H 的联合测量以及贝叶斯混合模型捕获了深厚壤土中小麦水分吸收的土壤剖面


作物从土壤中吸收水分的情况取决于降雨状况（降雨量、季节性、降雨事件大小的频率分布）、土壤、作物和管理。本研究以小麦休耕系统中的冬小麦为重点，将氢 （δD） 和氧 （δ18O） 同位素的测量与贝叶斯混合模型 （MixSIAR） 和根长密度的测量相结合，以 （i） 量化从土壤到 3 m 深的作物水分吸收，（ii） 评估播种时土壤水分的影响， 土壤覆盖、季节性条件及其对土壤水分吸收概况的交互作用，以及 （iii） 探究产量与土壤水分吸收概况之间的关系。在不同处理和季节中，拔节时的水分吸收比例为 2.1：1.0：1.8：2.2，分为四个土层，顶部 0.2 m、0.20.4 m、0.41.2 m 和 1.2–3.0 m。在开花时，比率变为 5.2：1.0：1.7：2.0。干燥条件下表层土壤在拔节时的吸水率 （∼60 %） 高于潮湿条件下的吸水率 （∼30 %），在较深的层中则相反;供水对开花时水分吸收曲线的影响较小。与裸露地面相比，覆盖物有利于 0.42.0 m 土层的根系增殖和水分吸收。对于给定的土壤层，土壤水分与根长密度呈负相关。产量与拔节时 0.43.0 m 土壤的水分吸收呈正线性相关，表明在籽粒产量形成的关键时期，早期根系发育较快有利于深层土壤的水分吸收。我们讨论了我们的发现对农艺管理和育种的影响。