Above Ground Drip Application Practices Alter Water Productivity of Malbec Grapevines under Sustained Deficit

An objective of this study was to identify above ground drip application practices for winegrape that increase water productivity and mitigate water deficit-associated loss of yield. The influence of irrigation frequency on water productivity under two severities of sustained deficit irrigation was evaluated in field grown Malbec grapevines (Vitis vinifera L.) over three growing seasons. A weekly amount of water was delivered in a single irrigation event (1X) or apportioned into thirds and delivered in three irrigation events per week (3X). The least severe deficit (STD) had a 3-yr average maximum duty cycle (ratio of irrigation duration to irrigation interval) of 0.3, and vines irrigated 3X relative to 1X had higher water productivity each year due to a decrease in pruning weight. The most severe deficit (STD50) had a 3-yr average maximum duty cycle of 0.02 and vines irrigated 1X relative to 3X had higher water productivity due to a reduction in pruning weight in 2012 and an increase in yield in 2013. The fruit produced from vines irrigated at the frequency with highest water productivity under each deficit severity contained a lower concentration of anthocyanins. While treatment combinations did not alleviate a water-stress associated reduction in yield, results provided new information about grapevine water use efficiency that can be used to select combinations of irrigation frequencies and duty cycles with potential for increasing water productivity.