Innovative undertrellis management for vineyards

Innovative undertrellis management for vineyards

Summary

The majority of eastern winegrape growers maintain the area under the grapevine trellis with herbicides, considered to be the easiest and most cost effective strategy. This project is designed to explore the use of cover crops or mowing in the area under the trellis. Green growth under vines is often viewed as detrimental, competing with vines for water and nutrients. However, many growers endeavor to reduce pesticide use and are therefore seeking viable alternatives. We studied under vine alternatives in several different settings. We monitored small-scale cover crop demonstration plots in eight commercial vineyards. Two research trials were maintained, one focusing on cover crops and one on under vine mowing. The season’s activities were documented in a blog; reports are also listed on our program website. Four powerpoint presentations were given to a total of 125 wine industry members representing four states. An additional 105 non-industry people heard presentations on this work. Five field tours were given to 53 people, including the Cornell viticulture class. Project updates appeared in five publications. Upcoming events this winter include a second webcast and two presentations to industry.

Objectives/Performance Targets

15 growers adopt mowing and/or green covers under the trellis on a total of 400 acres, reducing leachable nitrate by ≥ 10%, reducing or eliminating herbicides, and reducing canopy management inputs, saving $210/acre while maintaining or improving yield and quality.

The milestones relevant to this season are listed below. We met with the five grower advisors in March, 2013 to discuss project goals. They agreed to maintain existing demonstration plots; a few seeded additional under-vine covers in a portion of their vineyard, a total of 27.5 acres (up from 17.25 acres in 2012). Each vineyard was visited during the summer to gauge progress with the project. We met with this group again December 3 to review performance of covers and gather suggestions for 2014.

• Jan. 2013: A.Wise spoke at Viticulture Session of LI Agricultural Forum, Riverhead, Jan. 11, 50 attendees. A planned April, 2013 meeting with Cornell viticulturist Dr. Justine Vanden Heuvel (under-vine cover project with annual species) and A.Wise did not take place due to scheduling conflicts. We agreed that a webcast would be easier. A.Wise spoke about the project at three additional grower meetings.
• Winter 2013: A call for additional cooperators was made at the LI Agricultural Forum, at the March 26 meeting and via the Long Island vineyard manager list serv (Feb. 5). Our original goal was 5 additional growers. Two new growers agreed to plant trials while several of the grower advisor group expanded their plantings.
• Winter 2013: We originally requested interested growers to submit a plan to the grower advisor group for review. That has not taken place, rather we have presented collective results to the new growers and helped with decision making. Some of the growers spoke directly with one another. Our industry is small, growers felt the formal process unnecessary.
• Feb.-Oct. 2013: A total of 27.5 acres in 8 vineyard blocks (one grower had demos in two blocks) were maintained with under trellis covers in 2013. We hosted five field meetings and tours from July through October.

Accomplishments/Milestones

Powerpoint presentations were given to industry four times in 2013 – LI Agricultural Forum Jan. 11 (50 attendees); March 26 grower meeting sponsored by local ag dealer (15); two NJ twilight meetings (60). Three powerpoint presentations to non-industry audiences included March 6 Master Gardeners (40); March 13 tasting room staff training (45); April 13 SUNY Farmingdale students/home growers (20).

Research updates appeared in 5 publications : Feb. 5 and March 26 on Long Island Vineyard Manager list serv (75 subscribers); Feb. issue of Suffolk County Agricultural News (circ. 302); April 4 Long Island Fruit & Vegetable Update (circ. 204, goes to 12 states); photo/caption in NY Veraison to Harvest newsletter (circ.800); photos and reports on program website.

Research trials – We maintained an under-vine mowing trial in a Merlot block at the Long Island Horticultural Research and Extension Center and an under-vine cover crop trial in a commercial vineyard, cv. Syrah. Lysimeters were installed April, 2013 to analyze leachate for nitrate-nitrogen. We collected data from these blocks season long. For additional results and discussion, please visit our website http://ccesuffolk.org/viticulture. In 2013 through mid-December, we had 388 hits on our webpage with 330 being unique views (different computers).

Field plots tour – We hosted the following field meetings: Cornell professor Justine Vanden Heuvel & grad students toured plots July 9; July 11 Plant Science Day, tour/discussion of mowing trial (10); Aug. 22 at a grower advisor vineyard (8) and Sept. 9 at the cover crop trial (3). The Cornell viticulture class (27) toured the mowing trial, listened to a discussion of the project on Oct. 3.

Blog – The blog was set up on March 1, 2012. There were 12 posts in 2013 with 588 page views. The blog is intended to provide project updates including photos. http://iutmforvineyards.blogspot.com/. We asked one of our Cornell undergraduate interns to contribute to the blog this summer. He helped with posts and conducted an interview with one grower who mows under the trellis.

Future webcast and research presentations – A powerpoint presentation is planned for March 28 as part of a pest management meeting and tentatively at the winter meeting of the local ag dealer (Feb.). We are planning a webcast with Vanden Heuvel (Finger Lakes) and a Virginia researcher, to take place Feb-April. Both regions are doing under trellis work with annual and perennial cover crops.

Impacts and Contributions/Outcomes

Grower advisor plots: Seven grapegrowers maintained existing cover crop plots or seeded new plots, a total of 27.5 acres, up from 17 acres last season. Our original goal by year three (next year) was 400 acres in under vine covers. Though we have not yet formally addressed costs within this project, the combination of higher costs (higher than herbicide) and additional work has discouraged participation by growers with larger vineyards. This confirms findings in other studies that for many growers, business decisions carry equal or greater weight than environmental benefits. If under vine covers are considered together with vineyards that are mowing under the trellis, estimated acreage is 150-200, or about 10% of the region’s acreage.

The 2013season saw some extreme weather with 10-13” of rain in June followed by drought conditions July through October. There was some frustration with escape weeds getting up into the canopy as the fixed fruiting wire is only 28-36” high. It was necessary to address taller escape weeds at least once a season. Growers used a push mower (mowed high), machetes or weed whackers. There was discussion in the December 3 grower advisor meeting that perhaps weed whackers are not the most ecological option. The thickness of the thatch in no mow fescue plots reduced escape weeds but there is a big concern about rodent damage over the winter. One of seven growers has reported rodent problems.

After several seasons, we can offer the following observations about under vine covers. Results from vineyard to vineyard have been variable. This is to be expected with different soils, varieties, mesoclimates, seed sources etc. A December 6, 2013 e-mail exchange with Dr. Thomas Björkman, Cornell University professor of vegetable crops physiology, provided additional information cited below.

Site preparation: Some growers effectively used glyphosate prior to planting to clear out existing weed populations. Tillage by hand or machine prior to planting can also accomplish this; additionally, tillage is helpful in breaking up compacted soil. Soil compaction under the trellis is common in vineyards. Establishment of under vine cover crops is improved with some type of tillage.

Clover: In several vineyards, vines with clover were significantly larger and fruit ripening was delayed. Clover is not suitable for heavier soils and/or later ripening varieties such as Cabernet Sauvignon. In one newly planted vineyard, the grower felt young vines benefited from the release of nitrogen (N) by clover (no supplemental N was required). Unfortunately, the release of N is unpredictable in both timing and amount, making it somewhat riskier for mature vines. Stimulation of growth in the latter half of the season is detrimental to fruit quality and vine health. According to Björkman, Dutch white clover is the only type which stays low enough and persists well. Other types are too tall and/or will last only a few years. In our cover crop trial, we have noted that the percentage of Dutch white clover was much lower this season than last.

Fescue: While slow to start, the No Mow established a thick carpet in most blocks. It grows to about 10” then flops over. Vines in fescue plots were visually water stressed and N deficient during the extended late summer drought. Björkman speculates that since grasses have about 1000 times the root length as vines, irrigation might not overcome this due to the massive volume of grass roots. Future work must address N deficiency in fescue plots.

Other potential cover crop species: Björkman recommended in the future comparing different types of low growing grass especially turf types as there will likely be small but potentially important differences in their performance. Unfortunately, there are few other options for perennial covers in the under vine area. The ideal candidate establishes well and is competitive enough to keep escape weeds to a minimum but not significantly competitive with vines. We are contemplating future work with subterranean clover, which we have worked with in years past. This species becomes dormant in the summer, resuming growth in the fall. In our previous trial, plots were decimated by low winter temperatures. However, with warmer winters the last five years, perhaps winterkill will not be as much of an issue.

Rodents: One block with fescue and clover plots had a significant rodent problem, including damage to trunks. Other growers have not seen this, nor have we seen problems in either research trial.

Under trellis mowing trial summary: This trial involves four treatments: T1 – season long mowing (4 times); T2 – glyphosate only (2x); T3- mowing (2x plus glyphosate late June); and T4 – mowing (3x plus glyphosate late July). As in 2012, there were no significant differences in shoot length or shoot diameter in 2013. Pruning weights revealed that where vines were mowed for most of the season (T1 & T4), pruning weights were lower. This is likely due to increases in late season shoot growth and growth of lateral shoots (originating from the leaf axil of green shoots). Vine nutrition, as determined by petiole analysis, was similar for all treatments. There were no meaningful differences in yield or fruit ripeness at harvest. We were hoping that the use of competitive green covers would reduce berry size (higher skin:flesh is desirable in reds for color and flavor compounds) but we have not been able to document this effect. Lysimeters to gauge nitrate-nitrogen leaching were installed April, 2013. We collected five water samples; results suggested differences between treatments with the highest ppm in glyphosate plots.

Under trellis cover crop trial summary: This trial involves four treatments: T1 -glyphosate only (2x); T2 – Dutch white clover; T3 – No Mow fescue mix; and T4 – a combination of clover and No Mow, all seeded in spring, 2011. In 2012, the clover dominated the no mow in T4 plots; however, in 2013, clover in both T2 and T4 died back somewhat. As in previous seasons, there were no significant differences among treatments in shoot length or in shoot diameter. The six central vines in each plot were pruned on December 11. Vines in no mow plots (T3) were smaller than vines in glyphosate and clover plots (T1 & T2, respectively). This was likely due to differences in late season shoot growth and growth of lateral shoots. Pruning weights in the clover and herbicide plots were similar. We had expected the clover to stimulate shoot growth as seen in several grower advisor plots. In petiole analyses, clover plots displayed higher N while no mow plots had lower N levels. The two treatments with clover had significantly lower phosphorous and calcium. Phosphorous fertilization is often recommended when establishing clover for forage. Lysimeters to gauge nitrate-nitrogen leaching were installed April, 2013. We collected five water samples in May and June. Results suggested differences between treatments, with samples from clover plots higher in nitrate-N. However, the erratic performance of the lysimeters due to the extended drought prevents any firm conclusions.

Additional information and data can be found in the progress report posted on our website: http://ccesuffolk.org/viticulture.

• Under trellis mowing trial dates, percent weed cover
• Under trellis mowing trial vine measurements
• Under trellis cover crop trial vine measurements

• Under trellis mowing trial with lysimeter
• Under trellis mowing trial harvest data
• Under trellis mowing trial lysimeter results
• Under trellis cover crop trial percent cover
• Under trellis cover crop trial harvest data
• Under trellis cover crop trial lysimeter results
• under trellis clover in a commercial vineyard

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