Deficit irrigation and canopy management practices to improve water use efficiency and profitability of wine grapes.

Background In 2012, ca. 69% of vineyards for the production of wine in South Africa were irrigated and/or established under drip irrigation compared to less than 23% in 1996. Water savings obtained by using drip irrigation are in line with the optimal use of water resources as prescribed by the South African National Water Act no. 36 of 1998. The positive and negative effects of water constraints on grapevines have been reported on numerous occasions. However, most of the irrigation research in South Africa on wine grapes was carried out in flood or micro-sprinkler irrigated vineyards. Although the positive effects of canopy manipulation on the quality aspect of wine have been reported, all grapevines regardless of the canopy manipulations applied, received the same irrigation volumes and irrigation applications were indicated very vaguely or not at all. Therefore, there is no knowledge regarding the water requirement or usage of different canopy manipulated grapevines. Canopy management also requires a lot of labour inputs. In 2010, labour costs accounted for 41% of the total production costs of wine grapes. The effect that different irrigation strategy and canopy management combinations will have on the water requirement, vegetative growth, yield components, wine quality, labour inputs, and the economic implications thereof, has not previously been investigated. In 2010, representatives of the South African wine industry’s Breede River region approached two researchers (Soil and Water Science Programme) of ARC Infruitec-Nietvoorbij to investigate implementing deficit irrigation as a means to manage grapevine foliage growth. This would enable farmers and growers to plan and apply specific irrigation and canopy management practices for their individual vineyard needs, and in so doing, managing limited and expensive resources, i.e. water, electricity and labour, to produce the economically viable grapes. Knowledge could also aid viticulturists and irrigation consultants with their recommendations for scheduling individual vineyard blocks. The aim of this field trial was to determine the effect of different drip irrigation strategies and canopy manipulation combinations on the vegetative growth, plant water potential, water usage, yield, overall wine quality and profitability of Shiraz grapevines in a semi-arid region.