Application of a daily crop water stress index to deficit irrigate Malbec grapevine under semi-arid conditions

Authors: Shellie, Krista; King, Bradley - Brad

Submitted to: Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/19/2020
Publication Date: 10/22/2020
Citation: Shellie, K., King, B.A. 2020. Application of a daily crop water stress index to deficit irrigate Malbec grapevine under semi-arid conditions. Agriculture. 10(11). Article 492. https://doi.org/10.3390/agriculture10110492.
DOI: https://doi.org/10.3390/agriculture10110492

Interpretive Summary: Many wine grape production regions are located in arid and semi-arid climates where irrigation is used as a management tool to maintain vine balance, induce beneficial changes in berry composition, and increase water productivity. The lack of a rapid, automated method for monitoring vine water status between irrigation events limits the ability of vineyard managers to maintain a desired, consistent level of water stress severity in the grapevine during berry development. A leaf-surface-temperature-based crop water stress index (CWSI) for quantifying plant water status has had limited use in grapevine due to the difficulty of determining upper and lower temperature threshold values for non-transpiring and fully-transpiring vines. The objectives of this study were to determine the sensitivity of CWSI values to irrigation events and amounts and relate CWSI values with midday leaf water potential, juice carbon isotope ratio, yield components and berry composition. The daily CWSI was lower on the day after an irrigation event and increased daily between irrigation events. The amount of decrease and rate of increase corresponded inversely with irrigation amount. All three indicators of vine water status detected an increase in stress severity as irrigation amount decreased. Under the semi-arid conditions of this study, daily CWSI values were responsive to irrigation events and amounts. Integrating a daily CWSI with automated remote sensing into a precision irrigation system can provide irrigation decision support for managing water stress severity in grapevine.

Technical Abstract: Precision irrigation of wine grape is hindered by the lack of an automated method for monitoring vine water status. The objectives of this study were to: calculate a daily Crop Water Stress Index (CWSI) for wine grape (Vitis vinifera L.) cultivars Malbec and Syrah irrigated to supply 35, 70 or 100% of estimated water demand (ETc); measure CWSI response to irrigation events and amounts; and relate the CWSI with midday leaf water potential (LWP), juice carbon isotope ratio (d13C), yield components and berry composition over three growing seasons. The daily CWSI was lower on the day after an irrigation event and increased daily between irrigation events. The amount of decrease and rate of increase corresponded inversely with irrigation amount. All three indicators of vine water status detected an increase in stress severity as irrigation amount decreased; however, the response varied by year and cultivar. Seasonal weekly CWSI and LWP values identified differences among each irrigation amount in two out of three years. In Malbec, decreasing the amount of water from 100 to 35% ETc decreased berry fresh weight, increased the seasonal weekly CWSI, decreased the seasonal weekly LWP, and increased juice d13C. In Syrah, decreasing the amount of water from 70 to 35% ETc increased the concentration of total anthocyanins, increased the seasonal weekly CWSI, decreased the seasonal weekly LWP, and, in one out of three years, increased juice d13C. Under the semi-arid conditions of this study, daily CWSI values were responsive to irrigation events and amounts. Under arid conditions, integrating a daily CWSI with automated remote sensing into a precision irrigation system can provide irrigation decision support for managing water stress severity in grapevine.