S20 - Session P2 - Modeling evapotranspiration of off-season Table grapes vines grown in bi-annual cycles

Authors: Yishai Netzer *, Noa Ohana-Levi, Roni Michaelovsky, Rachel Sarel, Tovit Rosenzweig

Background: The Jordan Valley in Israel is a hot desert area. In order to advance the date of harvest, the vines are grown in two annual cycles. The vegetative summer cycle (May to November), without greenhouse coverage, and the winter reproductive cycle, under greenhouse conditions (December to April). Objective: Determining seasonal crop water use (ET c ) of off-season table grapes vines grown under unlimited water supply in an arid region and to establish the relations between ET c and vegetative and meteorological conditions. Materials and methods: Water use of grapevines ( Vitis vinifera 'Early sweet') was measured in 4 drainage lysimeters and 2 weighting lysimeters for 2 growing seasons (2020-2021). The lysimeters were installed in a 0.27 ha vineyard. The vines were drip irrigated at hourly intervals. The volume of water supplied each day exceeded the estimated vine water consumption by 25-50% to ensure continuous moisture conditions of the soil. The leaf area index (LAI) was measured weekly with the SunScan Canopy Analysis. Meteorological data were measured at two stations, inside and outside the greenhouse. Results: Daily ET c ranged from 0.97 to 2.51 mm d -1 during May 2021 in the greenhouse, and between 4.4 to 7.6 mm d -1 during August 2021 without the plastic cover. The seasonal ET c calculated measurements were 106 and 626 mm day -1 during the 2021 winter and summer seasons, respectively, while average seasonal crop coefficients (K c ) were 0.23 and 0.53 respectively. The LAI-K c polynomial regression coefficient was high for the summer measurements (R 2 = 0.90) and moderate (R 2 = 0.48) while applying the winter measurements. The results obtained in the summer are consistent with the literature, however, it is necessary to examine in-depth the effect of greenhouse and winter conditions on the ET c of the vines. Continued careful collection of the data will in the future allow for nonlinear modeling and prediction of ET c .