Abstract
Midday stem water potential (SWP) is rapidly becoming adopted as a standard tool for plant-based irrigation management in many woody perennial crops. A reference or “baseline” SWP has been used in some crops (almond, prune, grape, and walnut) to account for the climatic influence of air vapor pressure deficit (VPD) on SWP under non-limiting soil moisture conditions. The baseline can be determined empirically for field trees maintained under such non-limiting conditions, but such conditions are difficult to achieve for an entire season. We present the results of an alternative survey-based approach, using a large set of SWP and VPD data collected over multiple years, from irrigation experiments in olive orchards located in multiple countries [Spain, United States (California), Italy, and Argentina]. The relation of SWP to midday VPD across the entire data set was consistent with an upper limit SWP which declined with VPD, with the upper limit being similar to that found in Prunus. A best fit linear regression estimate for this upper limit (baseline) was found by selecting the maximum R2 and minimum probability for various upper fractions of the SWP/VPD relation. In addition to being surprisingly similar to the Prunus baseline, the olive baseline was also similar (within 0.1 MPa) to a recently published mechanistic olive soil-plant-atmosphere-continuum (SPAC) model for “super high density” orchard systems. Despite similarities in the baseline, the overall physiological range of SWP exhibited by olive extends to about −8 MPa, compared to about −4 MPa for economically producing almond. This may indicate that, despite species differences in physiological responses to low water availability (drought), there may be convergent adaptations/acclimations across species to high levels of water availability. Similar to its use in other crops, the olive baseline will enable more accurate and reproducible plant-based irrigation management for both full and deficit irrigation practices, and we present tentative SWP guidelines for this purpose.
Highlights
Crop productivity is closely linked to crop water use (e.g., Howell, 1990) and improving the efficiency of water use in agriculture has been an ongoing focus of research worldwide (e.g., Velasco-Muñoz et al, 2018)
The multi-year and multi-location studies provided a large data set with variable ranges in vapor pressure deficit (VPD) and stem water potential (SWP)
Olive SWP values from the entire data set varied over a wide range (−0.5 to about −6 MPa), but the highest values exhibited a pattern of decline with increasing VPD that was similar to the previously reported Prunus baseline (McCutchan and Shackel, 1992; Figure 1)
Summary
Crop productivity is closely linked to crop water use (e.g., Howell, 1990) and improving the efficiency of water use in agriculture has been an ongoing focus of research worldwide (e.g., Velasco-Muñoz et al, 2018). For some woody perennial crops, reducing or eliminating irrigation during specific periods of development (e.g., Chalmers et al, 1981) has been shown to produce economically beneficial effects, such as an improved fruit drying ratio in prunes (Lampinen et al, 1995), decreased fruit drop in peach (Li et al, 1989), and increased control of hull rot disease in almonds (Teviotdale et al, 2001) These crops may be good candidates for deficit water management strategies to increase overall water use efficiency. The number of fruits is relatively constant and pit hardening occurs (Rapoport et al, 2013) After this phase, the sensitivity of yield to water stress is reduced (Goldhamer, 1999; Moriana et al, 2003; Fernández et al, 2013; Girón et al, 2015; Ahumada-Orellana et al, 2017; Corell et al, 2020). Postharvest irrigation is not commonly studied, but Agüero-Alcaras et al (2021) reported no significant differences in season yield over a wide range of postharvest water stress conditions
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
