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Physiological tools to assess vine water status for use in vineyard irrigation management: review and update

Williams, L. E.
Acta horticulturae 2017 no.1157 pp. 151-166
Vitis vinifera, crop coefficient, cultivars, equations, evapotranspiration, field experimentation, grapes, irrigation management, leaves, lysimeters, rootstocks, scions, vegetation cover, vines, vineyards, water resources, California, Europe
Due to the competition for scarce water resources in the State of California and elsewhere around the world, agriculture needs to become more water use efficient. There are numerous means available to aid in the irrigation of vineyards to minimize applied water amounts and maintain yields of high quality. This paper will review various methods to assess grapevine water status and estimate vineyard evapo­transpiration (ETc) and provide an update with data recently obtained using numerous grape (Vitis vinifera L.) cultivars and V. vinifera scions grafted onto different rootstocks. A review of the use of leaf (Ψl), stem (Ψstem) and pre-dawn (ΨPD) water potentials as a means to assess vine water status will be followed by current research demonstrating that midday Ψl is the most convenient and accurate method to use. It will be demonstrated that all grape cultivars identified by many to date as isohydric (such as 'Grenache', 'Tempranillo' and 'Touriga Nacional') responded to water deficits similarly to anisohydric cultivars (such as 'Cabernet Sauvignon', 'Syrah' and 'Montepulciano') when grown in a replicated field trial. Several factors will be discussed as to why cultivars initially categorized as isohydric by others were not found so here. Lastly, the utilization of the amount of shade (percent shaded area) cast on the ground at solar noon (or percent ground cover) provides reliable estimates of a vineyard's seasonal crop coefficients (Kc) using the following equation: Kc = % shaded area * 0.017. The value of 0.017 has been found in several other studies in which vine ETc was measured with weighing lysimeters in Europe.