Spring 1995 (v7n2)
by Chuck Ingels, SAREP
[Editor's Note: The Grower Profile series is from a chapter in a forthcoming SAREP publication on cover cropping in vineyards. The publication includes contributions by numerous UC and Natural Resource Conservation Service researchers. It is edited by Chuck Ingels and Robert Bugg of SAREP,- Glenn McGourty, director, Mendocino Viticulture Specialist at the UC Kearney Agricultural County; and Peter Christensen, Cooperative Extension Center in Parlier.]
Zach Berkowitz is no stranger to vineyard cover cropping. The vice president of vineyard operations at
Domaine Chandon, Berkowitz has worked at the vineyard since 1974 and has tested a wide range of cover crop species and management practices. He oversees 1,300 acres of vineyards (mostly Pinot Noir and Chardonnay) in Sonoma, Napa, and Mendocino counties. The vineyards have a diverse array of conditions: Terrain ranges from flat to rolling hills to very steep hillsides; soils range from clayey to sandy, and from very deep to only one to two feet deep; rainfall varies from 20 to 45 inches; and both drip and sprinkler irrigation are used.
Domaine Chandon managers started using cover crops in vineyards prone to erosion, testing different quick-growing species. One mix that proved successful in a trial with the Napa County Resource Conservation District involved the perennial grasses meadow barley, Covar sheep fescue, and the annual forb crimson clover, which reseeds well. Now, however, the most commonly used no-till cover crop for hillside vineyards at Chandon is a mix of Blando brome and annual clovers (rose, crimson, and subterranean).
Green Manure
On less fertile sites, or where erosion control is needed in new vineyards, a green manure (plow-down) blend of common, purple, and Lana woollypod vetches, Austrian winter pea, bell bean, and either oat or barley is used. This mix is also used to build the soil in fallow areas before planting vines. On very high-vigor sites, Chandon managers have tried annual ryegrass and other aggressive grass mixes in various layouts to control excessive vine growth. The strategy that best reduced vine growth involved alternate row planting of these grasses. Berkowitz notes that grasses alone may take up large quantities of nitrogen from the soil. In most of Chandon's vineyards, he has observed that including a legume in cover crop mixes reduces competition and often results in improved wine quality. Chandon's vineyard managers are now testing California native perennial grasses and insectary blends.
Managing the cover crop has proven as challenging as selecting the right species. Like many growers, Berkowitz has found that the earlier in the fall the cover crop is planted (at least by mid-October), the better the cover crop seems to grow. But harvest is still taking place, and the only grain drill available is in high demand during this period. To avoid this conflict, cover crop seeding is started in mid-September in vineyards harvested early. After sowing, fall rains germinate the cover crop; no irrigation is applied to the cover crops in the fall or spring. The cover is mowed high (six to eight inches) once in the winter and again in the spring before vine flowering.
Berkowitz and the vineyard managers weighed the benefits of disking vs. nontillage for vetch mix described. Ultimately, they would like to avoid disking altogether. They like the biomass which vetch contributes, but the vetch frequently grows up onto trellises; also vetch dries the soil rapidly. To balance these issues, they cultivate every other row in early April and mow the alternating rows. The mowed rows are disked in May, giving more time for the cover crop to attract beneficial insects, spiders, and mites. This strategy has proved successful since it reduces the competition with the vines for water and nutrients in late spring. For the same reason, every row is disked in April during exceptionally dry springs. According to Berkowitz, this alternate row strategy has improved wine quality by reducing the green characters (lowering the malic acid level) of their sparkling wines.
Timing
As with most growers, not all Domaine Chandon's experiments with cover cropping have been successful. Berkowitz says Zorro fescue was planted in one vineyard in the fall between rows where vines were to be planted the following spring; the vineyard was to be managed without tillage. During the first year, the vines grew poorly and many of their leaves had fallen by late summer. The vines were again stressed in the second spring. Then the vineyard manger decided to disk part of the vineyard in early June, after which the vines appeared to recover rapidly. Berkowitz cautions that, if possible growers should hold off on cover cropping until about the second fall after planting the vines in order to avoid stressing them. If cover crops are used from the start, he notes, growers should consider disking alternate rows early in the spring, adding extra nitrogen and potassium, increasing the proportion of legumes in the mix, or planting the cover crop in a narrow band between vine rows.
The potential effects of Phylloxera on vines are also considered when choosing and managing cover crops. Berkowitz notes that there are two viewpoints on soil management practices in susceptible vineyards: 1) cover cropping without tillage, to avoid spreading the insects via soil cultivation tools, and 2) cover cropping with tillage to reduce competition of the cover crop with the already compromised vine root systems. As a result, tillage is used with cover crops in Domaine Chandon vineyards planted on AXR 1 rootstock. Green manure cover crops are often used to improve the root environment of susceptible blocks.
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