The widely used Feddes reduction function (FRF) was reviewed in the context of its merits and shortcomings for modeling root water uptake (RWU), crop transpiration, and soil water balance components. The empirical nature of the FRF was contrasted to few calibrations reported in the literature, and the conditions where the correct operation of the FRF was of limited importance were discussed. Some alerts regarding the feasibility of this function in hydrological studies were provided and reinforced by a case study with sugarcane under subtropical conditions. Available modifications of the FRF can improve RWU predictions under aeration stress but some conceptual imperfections make it inaccurate under drought stress and high compensated uptake. In such cases, the use of mechanistic RWU models in replacement of the FRF is recommended to accurately predict the actual transpiration dynamics. The calibration of the FRF by inverse modeling is feasible, although some of the FRF parameters are insensitive to model outputs.

广泛使用的 Feddes 归约函数 (FRF) 在模拟根系吸水量 (RWU)、作物蒸腾和土壤水分平衡组件的优缺点的背景下进行了审查。FRF 的经验性质与文献中报道的少数校准形成对比，并讨论了 FRF 正确运行的重要性有限的条件。亚热带条件下的甘蔗案例研究提供并加强了有关此功能在水文研究中的可行性的一些警报。FRF 的可用修改可以改善曝气压力下的 RWU 预测，但一些概念上的缺陷使其在干旱压力和高补偿吸收下不准确。在这种情况下，建议使用机械 RWU 模型代替 FRF 来准确预测实际蒸腾动力学。尽管某些 FRF 参数对模型输出不敏感，但通过逆建模校准 FRF 是可行的。