Effect of kaolin foliar application on grape cultivar Assyrtiko (Vitis vinifera L.) under vineyard conditions

Abstract

Context and purpose of the study – In the context of climate change and for the sustainable exploitation of Mediterranean vineyards, it is necessary to use new strategies to adapt to the new climatic conditions. High temperatures and radiation along with the increasing CO2 concentration in the atmosphere affect the maturity process, the technological maturity, as well as the physiology of the grapevine. The aim of the present study was to investigate the effects of kaolin foliar application on water relations, photosynthesis and berry composition of grape cultivar Assyrtiko, under drought conditions in Santorini and with two different training systems. 

Material and methods – The experiment took place in the cultivation season 2017-2018 in Santorini. There were two vineyards, one with the traditional training system of Santorini ‘kouloures’, and one with a unilateral Guyot training system, on vines of grape cultivar Assyrtiko. In both vineyards, there were vines that underwent kaolin application and control vines.  

Results – The use of kaolin reduced the leaf temperature in both training systems by 6.2 % for the unilateral Guyot system and by 6.9% for the traditional system. Chlorophyll concentration was higher after kaolin application for both training systems. Regarding the water potential, the kaolin application reduced water stress in both training systems, with significant difference observed in the unilateral Guyot system. Vine transpiration did not present statistically significant difference after the kaolin application. The photosynthesis of the vines after kaolin application was lower in comparison with the control vines, while in the case of stomatal conductance, there were no statistically significant differences observed. Kaolin delayed the maturation of the grapes in the case of the traditional training system. Water use efficiency was lower in the treatments with kaolin application compared to control vines. Regarding the other mechanical properties of the grapes and analyses of the must, there were no significant differences observed between the treatments. Therefore, the application of kaolin can be an effective and economical solution for the water saving of the vines in dry conditions, while at the same time it can improve the physiology of the plant and preserve the qualitative and quantitative characters of the grapes