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Under Trellis Management In Vineyards – Part 1:

Recently 'de-hilled' vineyard at NY Agricultural Experiment Station, Geneva, NY on May 6, 2014

Recently ‘de-hilled’ vineyard at New York  State  Agricultural Experiment Station, Geneva, NY on May 6, 2014

Alice Wise
Cornell Cooperative Extension of Suffolk County

This article originally appeared in the April 10, 2014 issue of the  Long Island Fruit and Vegetable Update, a publication of Cornell Cooperative Extension of Suffolk County. -TEM

‘Weed control’ is the traditional term that refers to the management of weeds or native vegetationin the 2-3 ft. strip under the trellis. Green growth in this area has long been viewed as undesirable competition for water and nutrients. We now understand that for vinifera on Long Island, it is not viticulturally necessary to have a totally weed free zone under the trellis all season long.

How much weed competition can vines tolerate? Over the last few seasons, we have learned that vine growth and yields can be substantially reduced in young vines (≤5 yrs old) that are maintained with under vine mowing. Established vines (>5 yrs old) with deeper root systems tolerate green growth under the trellis unless vines are otherwise stressed.

In local vineyards, a range of under trellis strategies are used: herbicides (preemergence, postemergence and combinations), hand hoeing, mechanical cultivation, under trellis mowing, weed whacking and cover crops. Hand hoeing is easy to implement but hard to maintain long-term. Mechanical cultivation can be effective if well- timed. Use of a cultivating implement requires a skilled tractor driver to avoid vine, trunk and root and trellis damage. Mechanical weeding long-term may reduce soil organic matter and increase soil erosion. Alternating cultivation with a timely postemergence herbicide such as glyphosate may address those concerns.

Under Trellis Mowing and Cover Crops. Over the last several years, we have been evaluating under trellis mowing and cover crops as alternatives to the use of herbicides. CCE-SC grape program research reports posted at . These methods have both advantages and disadvantages. In plots mowed season long, there has been a slight reduction in Merlot pruning weights. Over 6 seasons, there has been no impact on yield, cluster architecture or fruit quality. We use a single sided mower mounted on a custom frame, mowing 4-5 times/season. In industry, dual under-vine mowing heads are mounted on a row middle mower, significantly decreasing labor costs.

As with cultivation, mowing has to be timely. It is difficult to mow tall, dense stands of weeds. Also, mowing is best suited to laser planted vineyards as protruding trunks can be sliced. Attentive tractor driving can help to minimize this but with dual mowing heads, it is not always possible to avoid it.

Cover crops under the trellis represent another management option. In the mid-90’s, we established a trial with annual bluegrass and subterranean clover. Establishment was poor, leading to lots of escape weeds. The subclover also winter-killed. At the time, the goal was to find winter annual species that died down during summer months to minimize competition with vines.

Long Island Vineyard Trials. Recent experiences however suggest that some competition during the summer months may be desirable. In trials the last few years, under-vine fescue has reduced vine size and in some years, vine nitrogen status. A reduction in vigor might be beneficial in wet seasons and/or for vigorous varieties. Excessive competition can be overcome with timely irrigation and foliar nitrogen. Various types of clover have also been evaluated.

Results have varied from site to site, ranging from no impact on vine size to a pronounced stimulation of growth. Clover is best suited to sandier sites and earlier ripening varieties to avoid any undesirable increase in vine size. Establishment of green covers can be challenging especially on a large scale. Seed can be expensive, it pays to shop around. Site preparation requires removal of existing weeds, often accomplished with glyphosate, usually followed by light cultivation via raking, hand hoeing or use of a cultivating implement. Some type of pre-seeding cultivation is helpful if compactness is evident. Cover crop seeding is done by hand or with a push spreader. Some growers have skipped cultivation but rather have seeded and then scratched in the seed with rakes. Seeding has been done successfully in both spring and fall. It may be necessary mid-summer to deal with taller escape weeds before they go to seed, usually accomplished with weed whackers or mowing. (AW)


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