Transpiration of table grape (Vitis vinifera L.) trained on an overhead trellis system under netting

Abstract

The quantification of transpiration and corresponding basal crop coefficients is crucial for appropriate irrigation scheduling of drip-irrigated crops. Besides basal crop coefficients already published, there is the announcing need for setting values for the new growing practices such as cropping under netting. In this paper, measurements of unstressed table grape transpiration and basal crop coefficients under netting have been taken. Vineyards of two seedless cultivars (Crimson and Autumn Royal) were trained on an overhead trellis system which permitted the ground cover to reach values up to 90 %. Two campaigns of mid-season measurements were performed using one of the heat pulse techniques available (that known as the T max approach). Obtained values for average seasonal daily transpiration ranged between 3.9 and 4.4 mm day−1, for both cultivars, depending on the period considered. Weekly averages of the basal crop coefficients, from mid-May to end-September, ranged from 0.47 to 0.87. A polynomial equation was fit to the measured basal crop coefficients as a function of fraction of thermal units. After further validation for other cultivars with different cumulative thermal requirements, this equation could be considered helpful for farmers as a practical estimate of the table grape basal crop coefficient under the netting.