Winterizing wine grapes – Good Fruit Grower

—by Melissa Hansen, Washington State Wine CommissionResearch assistant Zilia Khaliullina weighs Chardonnay grape clusters in mid-September as a part of a venture associated to irrigation methods to assist winterize grapevines at Washington State College’s Roza analysis winery close to the Irrigated Agriculture Analysis and Extension Heart in Prosser. (Ross Courtney/Good Fruit Grower)Winter preparation for winery sustainability is undeniably necessary for wine grape growers in Washington and different northern grape-producing areas. Growers use irrigation to arrange vines for winter survival, but there’s been little scientific analysis on this space. A brand new analysis venture supported by the Washington wine trade goals to discover ways to greatest winterize grapevines with out compromising wine high quality. Washington State College’s Markus Keller, Chateau Ste. Michelle Distinguished Professor in Viticulture, leads the brand new four-year venture that was awarded a grant this 12 months from the Washington State Grape and Wine Analysis Program. This system is funded by contributions from the Washington State Wine Fee, Public sale of Washington Wines, Washington State College and state taxes collected on all wines offered. This venture suits nicely with Keller’s ongoing analysis program that focuses on how environmental elements and winery administration practices affect crop physiology of wine and juice grapes. Moreover, his analysis staff collects important temperature data yearly to trace grapevine chilly hardiness to assist growers decide when chilly safety measures needs to be initiated (see “Winery pruning strategy minimize chilly harm after frigid climate” ).The concept behind the analysis is to maximise each winter hardiness and wine high quality. Greatest-practice suggestions based mostly on science can then be developed for the Washington wine trade. Whereas there are strongly held however diverging opinions about “best-practice” approaches amongst wine trade members, Keller stated a number of the practices are based mostly on a misunderstanding of grapevine perform. Irrigation managementIrrigation is commonly used as a software to encourage chilly acclimation. For instance, one strategy to grapevine winterization is to cut back irrigation earlier than harvest, to keep away from new development and induce hardening off, although with out overstressing the vines. Such an strategy relies on a misunderstanding of grapevine perform: There isn’t a scientific proof for a connection between harvest date, preharvest water administration and vine hardening off, stated Keller. He defined that inexperienced shoots start to lignify proper after budbreak, though it occurs internally and growers can’t see it. With out lignification, shoots can’t transport water and due to this fact can’t develop. Shoot browning, against this, marks the demise of the outer cell layers and normally begins earlier than veraison. It has been considered a prerequisite for bud dormancy, however different environmental elements could also be concerned, similar to temperature and day size. For instance, within the Pacific Northwest, grapevine buds go dormant when the day size shortens to about 13 hours, which could be a number of weeks after the shoot base begins to show brown. Higher understanding of the grapevine dormancy cycle and its hyperlink, if any, with shoot browning is required.In a earlier subject trial with Cabernet Sauvignon in Washington, Keller discovered no impact on bud or cane chilly hardiness from cluster thinning (35 p.c yield discount) or diminished water provide (50 p.c discount from customary regulated deficit irrigation earlier than or after veraison). One other trial with fourfold variations in water provide to Cabernet Sauvignon grapes in Colorado discovered that though shoot development and berry measurement had been impacted by the irrigation remedies, bud and cane chilly hardiness within the winter was not influenced. Different trials in Washington and elsewhere have discovered no hyperlink between harvest date and chilly acclimation.Viticulture researcher Markus Keller pitches in for the harvest work of the analysis block. (Ross Courtney/Good Fruit Grower)Root protectionThere is a necessity to guard grapevine roots within the winter. In contrast to the aboveground tissues, roots neither go dormant nor harden off for the winter. Earlier analysis has proven that the deadly temperature (50 p.c harm stage) for roots is roughly 22 levels Fahrenheit. Roots in dry soil are extra susceptible to sudden temperature modifications, thus, customary apply in Washington is to refill the foundation zone to subject capability on the finish of the season. However how a lot water is basically wanted for root safety? Is it subject capability, or can growers have satisfactory root safety with much less water, which can result in higher vigor administration the next spring?One other unanswered query referring to root safety is the timing. It’s assumed that this further irrigation ought to happen after harvest, to keep away from “diluting” grape high quality, regardless that Keller confirmed in earlier analysis there was no preharvest dilution impact from irrigation except the water was utilized from overhead sprinklers. In that research, he discovered berries did take up water throughout the pores and skin when their floor was moist, however drip irrigation had no dilution impact. Nonetheless, some winemakers nonetheless encourage growers to withhold preharvest irrigation.Water is a limiting consider wine grape manufacturing in Japanese Washington. In drought years when irrigation districts should scale back volumes and finish deliveries sooner than regular, the choice to irrigate the foundation zone earlier than harvest could possibly be useful. Additionally, in years when harvest is delayed and stretches previous water supply dates, growers may fill the foundation zone whereas they nonetheless have entry to water.Khaliullina luggage pattern clusters for extra evaluation. (Ross Courtney/Good Fruit Grower)Area trial designThe new venture, which bought underway this summer season, is difficult. It entails two own-rooted varieties, three completely different irrigation remedies and assorted practices of late-season irrigation to fill the foundation zone in each mixture:—Normal regulated deficit irrigation (RDI) of managed water deficit from fruit set to reap.—Normal RDI with elevated water after veraison.—Normal RDI with decreased water after veraison.—Irrigation to fill high 3 toes of soil to 26 p.c soil moisture (subject capability) earlier than or after harvest.—Irrigation to fill high 3 toes of soil to twenty p.c soil moisture earlier than or after harvest.The varieties chosen — Chardonnay and Cabernet Sauvignon — span a spectrum from early to late harvest whereas having the same onset of bud dormancy. Keller’s analysis staff will measure soil moisture, soil temperature, leaf water standing, trunk sap stream, shoot development, shoot browning, pruning weight, chilly hardiness, budbreak share, bud fruitfulness and early-season vigor. Berries will likely be sampled for wine high quality metrics.“There may be a lot we don’t find out about grapevines and dormancy,” Keller stated. He added that grapes grown in Mediterranean climates, like that of California, obtain rain within the winter, and growers don’t have to fret about dormancy and chilly acclimation practically as a lot as Washington growers do. This analysis will reply some primary grapevine physiology questions in a sensible approach and make clear the connections, if any, between shoot development, lignification, browning, bud dormancy transitions and chilly hardiness. The brand new learnings will likely be translated into best-practice, science-based suggestions for the Washington wine trade.And whereas local weather change brings a brand new urgency to this analysis, with its extra frequent frosts in early fall and late spring and extra excessive arctic chilly snaps in winter, it’s an space overdue for research. We sit up for sharing this useful data with you within the subsequent few years.To be taught extra concerning the WSU chilly hardiness mannequin, go to: wine.wsu.edu/extension/cold-hardiness. 



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