The knowledge of the crop response to soil water deficit is essential to predict the actual crop water requirements under limited soil water conditions. The mathematical schematization of the crop response under RDI can allow identifying the exact irrigation timing. The threshold of soil water status below which crop transpiration decreases represents a key parameter for the water stress functions. The main objective of this paper was to investigate the effects of several RDI treatments, applied during the three stages of fruit growth, on soil-plant-water relations of drip-irrigated mandarin trees. Experiments were carried out in seven irrigation treatments: a control, irrigated at 125% of potential evapotranspiration measured in weighting lysimeters, ET_lys, during the whole year, and six RDI treatments in which 25% and 50% of ET_lys were applied during each of the three stages of fruit growth.

The critical threshold of soil water status expressed in terms of soil water depletion below which predawn (PLWP) and midday (MSWP) leaf water potential is affected by decreasing soil water content, were identified. The dependency of crop water status from the climate forcing, occurring under soil water contents higher than the critical threshold was also demonstrated. Moreover, a strong relationship between water stress integral (${\mathit{S}}_{\mathit{MSWP}}$) evaluated during the three stages of fruit growth, and the corresponding amount of water applied (irrigation and precipitation) was observed after normalizing the variables. The robust relationship between these two variables (R² = 0.83) confirmed that the water stress integral represents a good indicator of the plant-water relationship and allows the prediction of the total irrigation depth to be applied to achieve a desired stress level during the fruit growth. Moreover, this relationship depends on the irrigation schedule adopted to regulate the deficit, which includes the irrigation variables, such as irrigation dose and its variability.

了解作物对土壤缺水的反应对于预测有限土壤水条件下的实际作物需水量至关重要。在RDI下对作物响应的数学图示可以确定确切的灌溉时间。作物蒸腾量降低到的土壤水分状态阈值代表了水分胁迫功能的关键参数。本文的主要目的是研究在果实生长的三个阶段中应用的几种RDI处理对滴灌drip树的土壤-植物-水关系的影响。实验在以下七个灌溉处理中进行：对照，以称重溶渗仪ET _lys测得的潜在蒸散量的125％灌溉，在一年中，以及六个RDI处理过程中，在水果生长的三个阶段中的每个阶段都应用了ET _lys的25％和50％。

确定了以土壤水分消耗表示的土壤水分状况的临界阈值，低于该阈值时，黎明的（PLWP）和中午（MSWP）的叶水势会受到土壤水分含量降低的影响。还证明了在土壤水分含量高于临界阈值的情况下发生的作物水分状况与气候强迫的关系。而且，水应力积分之间有很强的关系（${\mathit{小号}}_{\mathit{MSWP}}$）在水果生长的三个阶段进行了评估，并在对变量进行归一化后观察到相应的灌溉水量（灌溉和降水）。这两个变量之间的稳健关系（R ² = 0.83）证实了水分胁迫积分是植物与水分关系的良好指标，并且可以预测总灌溉深度以达到果实期的理想胁迫水平。增长。而且，这种关系取决于用来调节赤字的灌溉时间表，其中包括灌溉变量，例如灌溉剂量及其可变性。