An Assessment of Wind Machine Performance for Vineyard Frost Protection

This 2012 project evaluated temperature changes resulting from wind machine operation for both upward-blowing wind machines and conventional horizontal-blowing machines. Measurements were conducted at dozens of locations in commercial vineyards throughout the counties of Santa Barbara, San Luis Obispo, Sonoma and Mendocino.

The study relied almost entirely on wind machines which had been previously installed by vineyard operations for their own frost protection needs, and which were operated by the cooperators during the study period whenever they felt that frost protection was needed. Instrumentation was installed at 34 wind machines; not all sites experienced frost conditions, but machines were operated sufficiently at 29 of the 34 sites. These included 22 sites with upward-blowing wind machines and seven sites with conventional machines. We compared the observed air temperatures at distances of 15, 30 and 60 m from each wind machine, compared to the predicted temperature values if the wind machines had not been operated.

Overall, the operation of the conventional wind machines showed useful temperature increases which were similar to results from previous studies, while the operation of the upward blowing wind machines had minimal effect on increasing air temperatures. Additional detailed studies were conducted with a medium-sized upward-blowing wind machine at a future vineyard site. Comprehensive temperature measurements were made using 52 sensors surrounding the machine in all directions, over 12 operation nights. Little or no temperature gains were observed from the operation of this machine under the particular conditions of the study.

Improved information on the relative benefits of different types of wind machines and their ability to alter vineyard temperatures is important for vineyard operations that require some form of frost protection. As water supplies for sprinkler frost protection become more limited, there is increasing attention being paid to wind machines as a potential alternative in many areas. This study will provide growers with useful information to help them to make the most informed frost protection decisions possible.

Modeling Grapevine Cold Hardiness as a Predictive, Site- and Cultivar-Specific Online Decision-Aid Tool for Vineyard Freeze Protection

Cold injury due to low winter temperatures remains an important environmental challenge in many grape-growing regions throughout the United States, but especially in the northern states. Grapevines are adapted to the recurring seasonal changes in temperature by being able to develop a certain tolerance of low temperatures that is termed cold hardiness. Cold hardiness follows a somewhat predictable seasonal pattern: an acclimation phase (gain of hardiness) in late fall precedes a period of maximum hardiness in midwinter which is followed by deacclimation (loss of hardiness) towards spring, as the vines prepare for budbreak. Yet fluctuations in temperature lead to ?noise? in this general trend, because lower temperatures are associated with acclimation, while higher temperatures are associated with deacclimation. During the first year of this three-year project we developed a prototype computer model of the changes in cold hardiness of grapevine buds during winter. This initial model uses time steps of one day along with the measured daily mean air temperature to calculate the daily change in bud hardiness, which is then added to the hardiness from the previous day. The model simulates natural changes by estimating daily increases or decreases in hardiness depending on temperature. It also integrates a genetic component by altering the mathematical equations for different grape cultivars. We started by applying our model to Chardonnay, Cabernet Sauvignon, and Concord; these three genetically distinct cultivars demonstrate the variation in cold hardiness dynamics that our model?s flexibility is able to explain. In its current version the model is able to explain 89{aed9a53339cdfc54d53cc0c4af03c96668ab007d9c364a7466e3349a91bf0a23} of the variation in bud hardiness for Cabernet Sauvignon and Chardonnay, and 82{aed9a53339cdfc54d53cc0c4af03c96668ab007d9c364a7466e3349a91bf0a23} of the variation for Concord. More cultivars, as well as different vineyard sites, will be added during the remainder of this project. We are currently integrating the model into Washington State University?s AgWeatherNet (http://weather.wsu.edu), a network of 132 weather monitoring stations distributed across the state of Washington, to allow prediction of grapevine cold hardiness throughout the state. This innovative tool, along with weather forecasts and cell phone applications, will aid in the anticipation of and response to potential damage from fluctuations in winter temperature and from extreme cold events. This will allow growers to plan the implementation of cold protection measures, adjust pruning practices, and, in the long term, facilitate site selection for new vineyard developments.

Grapevine Cold Hardiness: Developing a Data Base for California

The ultimate objective of this study is to develop a database of cold hardiness values for samples from the central coast region of California that can be used to develop a cold hardiness model. The model, taking into consideration the principle factors that influence grapevine cold hardiness, will be used to help growers predict the temperatures at which injury may occur. This will assist them in making decisions regarding their efforts to avert such injury through the use of wind machines, irrigation, and other vineyard management practices.

As of this date, this project has developed the necessary low temperature exotherm analysis system necessary to detect cold hardiness of grapevine buds and cane tissues. This has involved the acquisition and assembly of numerous electronic components and software to manage these components to enable the detection of the transition of the extra- and intracellular water in grapevine buds and cane tissues from a liquid to a solid state (ice). This transition is accompanied by the release of the heat of fusion. By using a computer-facilitated program to monitor the output of thermoelectric modules and the temperature in the freezing chamber, the low temperature exotherm event can be detected. The development of this system has unfortunately taken longer than anticipated and has only recently (December 18, 2001) been completed. Since this time, we have successfully identified the temperatures at which freezing of grapevine buds are occurring. We are now beginning to accumulate the database that will be necessary to develop the model.

PDF: Grapevine Cold Hardiness: Developing a Data Base for California

Evaluation of Microsprayers for Frost Protection in California Vineyards

The experimental site was a Chardonnay vineyard located near Los Alamos, CA. Plots were established during early March 1993 and data were collected from March 11, 1993 through May 20, 1993 and March 14, 1994 through May 23, 1994. The microsprayer (Wade Pulsator?) under evaluation uses a pulsing action that produces larger diameter droplet sizes, while maintaining lower application rates as compared to those found with conventional microsprayer design. This microsprayer produces a narrow band of water (approximately 24 inches wide) directed over the cordon of the vine. Microsprayers were installed in every vine row and mounted 22 inches above the cordon on every other stake, approximately 10.5 feet apart. A five acre block of microsprayers was compared to an adjacent sprinkler block. The sprinkler block had a typical design and installation for commercial coastal vineyards. Sprinkler spacing was 50.0 feet X 42.0 feet, using a conventional impact type head and a 7/64 inch nozzle. The water source for both systems was an above ground reservoir filled by pumping ground water. Water was passed through a perforated tube filter for the sprinklers and a sand-media filter for the microsprayer system. Water use was measured by a Rockwell sealed register meter. Data collected for the microsprayer and sprinkler blocks were bud temperature, air temperature, and relative humidity. Air temperature was also recorded at 18 inches from the cordon and the middle of the vine row (at cordon height). Environmental conditions monitored outside the vineyard were air temperature, wind speed and direction, and relative humidity. Environmental data were collected with Omnidata data loggers using a series of thermocouples for bud temperatures (attached at bud locations) and Physchem RH sensors’for air temperature and relative humidity. A data logger and associated sensors were located within the microsprayer and sprinkler blocks and outside the vineyard. Due to the low number of spring freezing events in 1993 and 1994, data collection was limited at the vineyard site. During the spring freezing events which were monitored, microsprayers provided a level of frost protection which was similar to that provided by sprinklers. Also, the use of microsprayers resulted in a savings in water use of approximately 80 percent during selected freezing events. This was a preliminary experiment and further research is needed before general recommendations can be given. Continuing studies will include a series of tests under controlled freezing conditions in a cold chamber.

Evaluation of Microsprayers for Frost Protection in California Vineyards

Reduction in water use or increased water use efficiency are important concerns for wine grape growers. However, conservation of water must not reduce productivity, wine quality, or increase production costs. Targeted systems have been used in tree fruit and citrus production to provide frost protection while reducing the amount of water used. Potential benefits of a targeted system, such as microsprayers, for frost protection in vineyards include: reduced water use; less reservoir capacity is required; lower equipment costs for installation (smaller pumps and pipe); and less energy use. The purpose of this experiment was to investigate the use of microsprayers for frost protection in a commercial vineyard. The experimental site was a Chardonnay vineyard located near Los Alamos, CA. Plots were established during early March 1993 and data was collected from March 11, 1993 through May 20, 1993. The objectives of this experiment are to determine if an alternate method of frost protection (targeted microsprayer system) for California grapes is feasible and to determine if this method is less water consumptive than current practices demand. The microsprayer (Wade Pulsator?) being evaluated uses a pulsing action that produces larger diameter droplet sizes, while maintaining lower application rates than those found with conventional microsprayer design. This microsprayer produces a narrow band of water (approximately 0.6 meters wide) directed over the cordon of the vine. Microsprayers were installed in every vine row and mounted 0.56 meters above the cordon on every other stake, approximately 3.6 meters apart. A 2 ha block of microsprayers was compared to an adjacent sprinkler block. The sprinkler block is a typical design and installation for a commercial coastal vineyard. Sprinkler spacing is 15.6 meters X 12.8 meters, using a conventional impact type head and a 2.78 mm nozzle. The water source for both systems was an above ground reservoir filled by pumping ground water. Water was passed through a perforated tube filter for the sprinklers and a sand media filter for the microsprayer system. Water use was measured by a Rockwell sealed register meter. 30 Data collected for the microsprayer and sprinkler blocks were bud temperature, air temperature, and relative humidity. Environmental conditions monitored outside the vineyard were air temperature, wind speed and direction, and relative humidity. Environmental data was collected with Omnidata data loggers using a series of thermocouples for bud temperatures(attached at bud locations) and Psychem RH sensors for air temperature and relative humidity. A data logger and associated sensors were located within the microsprayer and sprinkler blocks and outside the vineyard. Radiational freezing events occurred on 28 April and 14 May 1993. Data collected on these dates suggests that microsprayers were as effective as overhead sprinklers for frost protection. A second year of data was collected during the spring of 1994 to further quantify the level of frost protection provided by microsprayers and the amount of water savings.