Author
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Shellie, Krista |
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Submitted to: American Journal of Enology and Viticulture
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 2/1/2014 Publication Date: 3/1/2014 Publication URL: http://handle.nal.usda.gov/10113/59701 Citation: Shellie, K. 2014. Water productivity, yield, and berry composition in sustained versus regulated deficit irrigation of Merlot grapevines. American Journal of Enology and Viticulture. 65:197-205. Interpretive Summary: Many wine-producing regions in the world experience seasonal drought and irrigation is commonly used to stabilize yield and maintain or improve grape quality. In production regions where the amount of available water in the soil is insufficient to meet the water demand of the vine, irrigation is often used to intentionally induce a water stress in the grapevine. The practice of supplying less water than required by the vine is referred to as deficit irrigation. The ultimate goal of deficit irrigation in wine grape is to optimize berry composition for wine production without compromising yield and to increase water productivity. Water productivity is the amount of yield or net income of product produced per unit of water consumed. The objectives of this study were to measure how different deficit irrigation practices influenced the yield, berry composition and water productivity of the wine grape cultivar Merlot when grown under arid conditions. Three severities of a sustained water deficit and an irrigation treatment that induced greater water stress before than after berries developed color, were evaluated over three growing seasons under arid conditions. Yield, berry size and pruning weight decreased and water productivity sequentially increased as the amount of irrigation decreased from the standard amount to 35% of the standard amount. The increase in water productivity was due to a proportionally greater decrease in pruning weight relative to yield. The irrigation amount that produced the greatest quantity of fruit with desirable berry composition was the 70% of standard treatment. The irrigation treatment that induced greater water stress before than after the berries developed color utilized 15% less irrigation water and produced fruit of similar composition as the 70% of standard treatment but it had similar water productivity as the 70% of standard treatment due a reduction in berry size and lower yield. Technical Abstract: The wine grape cultivar Merlot (Vitis vinifera L.) was irrigated at incremental fractions of estimated crop evapotranspiration or a regulated deficit (RDI) regime to identify which practice best optimized water productivity and berry composition without compromising yield. Three severities of sustained water deficit (35% STD, 70% STD and STD) and an RDI treatment that alleviated preveraison water stress at veraison were imposed at fruit set through harvest over three growing seasons under arid conditions. The irrigation treatments affected the relative proportions of different sized berries and irrigation and berry size had independent effects on sugar and anthocyanin accumulation. Similar sized berries irrigated by RDI and 70% STD contained the same amount of sugar and anthocyanin per berry. Yield, berry size and pruning weight decreased and water productivity sequentially increased as irrigation amount decreased from STD to 35% STD. The increase in water productivity was due to a proportionally greater decrease in pruning weight relative to yield. The 70% STD treatment produced the greatest quantity of fruit with desirable berry composition; however, if irrigation water supply is limited, the RDI treatment produced fruit of similar composition as the 70% STD treatment utilizing 15% less irrigation water. |
