Practical Winery
65 Mitchell Blvd, San Rafael, CA 94903
phone: 415-453-9700 ext 102
email: Office@practicalwinery.com
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Summer 2011
GRAPEGROWING
Water management – Controlling canopy growth by regulating water to achieve yield and quality goals is fundamental to winegrape production. If sunburn and/or heat damage regularly causes crop loss, then working to better understand water relations for canopy management purposes in those blocks can benefit fruit quality.
Regularly monitoring both soil and vine water status will allow growers to see the effects of applied water and soil water disappearance on specific objectives for shoot growth, berry size, and ripening.
Knowing the relative amount of water vines can extract in high evaporative demand conditions and how quickly that moisture can disappear, will allow you to apply the right amount at the right time to minimize vine stress. Applying water each day of a heat spell will not reduce vine water stress if soil moisture content was too low before starting.
Leaf removal – In a region with high winter rainfall, controlling early season vine growth is accomplished by withholding irrigation until shoot growth slows, and by utilizing cover crops to deplete stored soil moisture.
Shoot thinning is required to maintain desirable spur positions and manage crop load. In most sites, those practices alone do not result in the desired level of fruit exposure; however in low vigor sites they may.
The quantity and quality of light on clusters and the timing of exposure has significant effects on fruit composition. The goal is to create a light environment in the canopy that achieves fruit quality targets yet avoids excessive heating of clusters. If a site frequently experiences sunburn or heat damage, then the severity of leaf removal must be reduced to improve quality.
In cool, foggy regions, leaf removal is essential for disease control and for fruit exposure, as dense canopies are common due to high soil moisture. Because hot periods are more infrequent than in warmer regions but not absent, determining optimal cluster exposure is more challenging in these regions.
Sprinkler cooling – Utilizing sprinklers for evaporative cooling is an option for some growers. When weather forecasts predict expected high ambient temperatures around 100°F or greater, sprinklers — either traditional impact or targeted systems — can be used to achieve evaporative cooling. Most research with over-vine sprinklers to achieve cooling has been conducted with impact sprinklers, which provide total vineyard floor coverage.
Over-vine targeted sprinklers and under- or over-vine micro-sprinklers, misters, etc. have also been used to provide cooling with reduced water use. Temperature sensors
inside “protected” blocks allow determination of when temperatures stabilize after turning on sprinklers, and help growers meet water conservation goals.
Sprinkler irrigation time required to reduce and stabilize vineyard temperatures may be surprisingly short, at which point there is no further temperature drop by maintaining overhead cooling. After the system is turned off, the cooling effect will continue as water evaporates off vine surfaces. The duration of this effect can be measured by temperature sensors in the vineyard block.
   
References
1. Dokoozlian, N. 2009. Foundations of canopy management: the contributions of Dr. Mark Kliewer. In Proceedings for the Recent Advances in Grapevine Canopy Management, International Symposium. N. Dokoozlian and J. Wolpert (organizers), pp. 43-52. University of California, Davis.
2. Mullins, M.G., A. Bouquet, and L.E. Williams. 1992. Biology of the Grapevine. Cambridge University Press, Cambridge, UK.
3. Williams, L.E., and P. Baeza. 2007. “Relationships among ambient temperature and vapor pressure deficit and stem and leaf water potentials of fully irrigated, field-grown grapevines.” Am. J. Enol. & Vitic. 58: 173-181.