Determining a Midday Stem Water Potential Threshold for Irrigation of Table Grapes Water potential threshold

Abstract

Sustainable table grape production depends on efficient water supply. Water potential is a useful indicator of water constraints in grapevines. In this regard, midday stem water potential (ΨS) is considered to be a better indicator of grapevine water status than leaf water potential (ΨL). The objective of the study was to determine a water potential threshold to set soil water refill lines for table grape irrigation. However, in previous studies carried out locally, only ΨL was measured. The relationship between ΨS and ΨL was determined for ten selected table grape cultivars. Since there were no differences between cultivars, a single equation could be used to convert midday ΨL measured in previous studies with table grapes to ΨS. Vegetative growth, berry mass and colour, as well as juice total soluble solids (TSS) data were pooled, and related to midday ΨS. This showed that -0.8 MPa seems to be a ΨS threshold for water constraints in the pre-harvest period that will allow sustainable growth and berry size for anisohydric table grape cultivars. The optimum ΨS for berry colour is between -0.8 MPa and -1.0 MPa. Consequently, a midday ΨS threshold of -0.8 MPa can be used to set refill points for irrigation where soil water content is measured on a regular basis in table grape vineyards.

Effect of Irrigation with Treated Municipal Wastewater on Vitis vinifera L. cvs. Cabernet Sauvignon and Sauvignon blanc in Commercial Vineyards in the Coastal Region of South Africa - Vegetative Growth, Yield and Juice Characteristics

“…At pea size berry stage of the 2017/18 growing season, with the exception of the backslope DLD and footslope SLD plots, the irrigated treatments did not experience any water constraints according to thresholds for water stress levels proposed by Van Leeuwen et al (2009) for Sauvignon blanc and Myburgh et al (2016) for Cabernet Sauvignon grapevines (Fig. 3A-C).…”

“…3C). According to water constraint thresholds, the maximum Y S measured at the footslope DLD plot fell under Class IV, namely "high water constraints", which is regarded as ideal to produce quality Cabernet Sauvignon wine on a clay soil (Myburgh et al, 2016). The substantially higher Y S measured at the footslope DLD plot during véraison and harvest was most probably a result of the high volumes of irrigation water applied at this plot (Howell et al, 2022b) and subsequent greater SWC (Fig.…”

Using Grapevine Water Status Measurements for Irrigation Scheduling of Table Grapes - A Review

“…It is evident that the water status classification based on grapevine water potential should be extended for table grapes to classify plant water status when the PAW in the soil is in the high range. Due to the problems with taking Y L measurements on horizontal canopies (Myburgh & Howell, 2022), only Y PD and Y S should be considered to develop water status classes for table grape responses to low levels of PAW depletion. There are also different rates of water constraint evolution for wine grapes in soils having different hydraulic conductivities (Myburgh, 2011b).…”

“…In a study to determine a water potential threshold to set soil water refill lines for table grape irrigation, the relationship between Ψ S and Ψ L was determined for ten selected table grape cultivars (Myburgh & Howell, 2022). A single equation could be used to convert midday Ψ L measured in previous studies with table grapes to Ψ S .…”

Relações entre atributos de solos de basalto e videiras \'Syrah\' em colheita de inverno no Estado de São Paulo

“…Para acompanhamento do estado hídrico da videira, durante o desenvolvimento da uva, em complemento as análises físico-hídricas dos blocos e perfis, foi realizado o monitoramento do potencial hídrico da videira (Ψ), no período que antecedeu o pintor até a colheita da uva, no perído de 111, 138 e 168 DAP, com o uso da câmara de Scholander (Scholander et al, 1965), modelo PMS 1003, da Soilmoisture®. Com o uso da câmara de Scholander foi medido o potencial hídrico do caule (S Ψ), que tem se mostrado uma sensível e confiável indicador do déficit hídrico da videira (Choné et al 2001;Cole;Pagay, 2015;Myburgh;Howell, 2022).…”