The pitfalls of water potential for irrigation scheduling

The water potential (Ψp), has been widely used as an indicator of plant water status for irrigation management purposes. The simple infrastructure needed for its measurement and its direct relation to basic plant physiological processes, have contributed to the popularity of the methodology. When used for irrigation scheduling, it is commonly assumed that an unavoidable relationship exists between plant transpiration (T), soil water content and Ψp. Nevertheless, it is worth remembering that variations in Ψp are not solely related to changes in soil water content, but are also an expression of the interaction between the plant and its environment. We used a soil-plant-atmosphere-continuum (SPAC) model to highlight the importance of considering such interactions through a series of in silico experiments. Our analysis shows that evaporative demand, the hydraulic architecture of the plant, and the texture and depth of the soil play key roles in the final Ψp observed. To establish irrigation programs based on Ψp, without considering the environmental and plant factors that influence it, can create the paradox of having a plant that suffers greater water stress even when high irrigation volumes are applied. The conclusions from our in silico analysis provide some warnings that should be considered when using Ψp to schedule irrigation.

This work was supported by project RTA2015-00089-C02-02 from the Ministry of Economy and Competitiveness of the Spanish government and by the European Union’s Horizon 2020 research and innovation program (No 730253). The authors would like to thank the “Juan de la Cierva Formación” funded by the Spanish Ministry of Economy and Competitiveness [grant numbers FJCI-2017-34086 andFJCI-2015-24109] for providing the funds for Dr. Omar Garcia-Tejera and Dr. Alvaro Lopez-Bernal.