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 five commercial vineyards. Two research trials were maintained, focusing on cover crops and under vine mowing. The season’s activities were documented in a blog; reports are also listed on our program website. Six powerpoint presentations and/or vineyard tours were given to a total of 146 wine industry members from two states. An additional 65 non-industry people heard presentations on this work. Articles in two newsletters reached 549 people in six states. Project updates appeared or will soon appear in six publications. The grower advisor group met December 17 to review results in their vineyards as well as in the research trials. Three powerpoint presentations are currently scheduled for winter 2015.

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. In 2014, we continued to maintain two research blocks. Four of the original eight cooperating growers and one new grower maintained under vine cover trials. Two growers expanded their plantings; a third grower seeded a large area but establishment was poor. Two vineyards are almost entirely in cover crops. That acreage together with trial areas equate to a total of 37 acres are in under vine covers. Each vineyard was visited during the summer to gauge progress with the project. We met with the five grower advisors December 17, 2014 to review performance of covers and solicit input for 2015 efforts.

1. March, 2014: A.Wise spoke about the project at a grape grower meeting hosted by the local ag supply dealer. 27 attendees
2. April 2014: A call for additional cooperators was made at the March grower meeting and via the Long Island vineyard manager list serv. While 5 additional acres were planted to cover crops, three growers elected to terminate their cover crops experiments, a total of about 2 acres. Reasons included removal of the entire vineyard block; undesirable effect on fruit ripening; and cover crop too tall, interfering with fruit zone and requiring too much work (trimming).
3. Winter 2014: 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 and helped interested parties with decision making. Some of the growers spoke directly with one another. Our industry is small, growers felt the formal process unnecessary.
4. -Oct. 2014: A total of 37 acres in 5 vineyards were maintained with under trellis covers in 2014. We hosted or participated in four tours from July through October.

Accomplishments/Milestones

Powerpoint presentations were given to industry three times in 2014: March 7 grower meeting sponsored by local ag dealer (27) and April 4 webcasts featuring under vine cover crop research being conducted by Drs. Justine Vanden Heuvel (Cornell) and Tony Wolf (VA tech) (24). Three powerpoint presentations to non-industry audiences included April 8 Master Gardeners (30); March 16 presentation to home growers at Hicks Nursery (20); August 21 presentation to Moriches Bay Garden Club (15).

Research updates appeared in 5 publications: Feb. 5 and March 26 on Long Island Vineyard Manager list serv (75 subscribers); Feb. and March issues of Suffolk County Agricultural News (circ. 331, goes to 4 states); April 10 Long Island Fruit & Vegetable Update (circ. 218, goes to 6 states); photos and annual reports on CCE grape program website (2830 hits Jan.1-Dec.7, 2014 with 2393 being unique views).

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/grape-program.

Field plots tour – We hosted the following field meetings and tours: July 15 tour of mowing trial by Sagtikos garden club (15); Aug 22 field presentation at NRCS Soil Health meeting (63); Sept 4 Plant Science Day, tour/discussion of mowing trial (12). Oct. 6, the Cornell viticulture class (20) toured the mowing trial, listened to a discussion of the project.

Blog – The blog was set up on March 1, 2012. There were 10 posts in 2014 with732 page views; there have been 1330 total page views over the course of the project. The blog is intended to provide project updates including photos. http://iutmforvineyards.blogspot.com/.

Future articles and presentations – The project will be discussed in technical articles in the February and March, 2015 Suffolk County Agricultural News. Cornell professor Dr. Justine Vanden Heuvel and I will each give presentations on our work with under vine strategies at the January 9, 2015 Long Island Agricultural Forum. Research results will be uploaded to the CCE grape program website winter 2015. Summary of the work will appear in the Annual Report of the Long Island Horticultural Research and Extension Center. http://www.longislandhort.cornell.edu/.

Impacts and Contributions/Outcomes

Grower advisor plots: Five grapegrowers maintained existing cover crop plots or seeded new plots. Cover crop acreage related to this project: 2012 – 17 acres; 2013, 27.5 acres; 2014, 37 acres. Our original goal by year three was 400 acres in under vine covers. If under vine covers are considered together with vineyards that are mowing under the trellis, estimated acreage is 110, or about 5% of the region’s acreage.

Why have growers been reluctant to adopt alternative under vine strategies? Though we have not yet formally addressed costs within this project, the combination of higher costs (higher than herbicide) and additional field 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. In addition, extended summer droughts in 2013 and 2014 caused moderate to severe drought stress symptoms. This occurred in vineyards with under vine covers as well as in vineyards utilizing under vine mowing. Drip irrigation reduced the severity of symptoms but did not completely mitigate the impacts of drought stress.

After several seasons, we can offer the following observations about under vine covers and under vine mowing. Results from vineyard to vineyard have been variable. This is to be expected with different soils, varieties, mesoclimates, seed sources and management. Included below are comments from Cornell professor of vegetable crops Dr. Thomas Björkman (12.6.13 and 12.15.14 e-mails). Dr. Björkman has been very helpful with this project.

Site preparation: Some growers effectively used glyphosate prior to planting to clear out existing weed populations. Tillage by hand or machine prior to planting is necessary to break up compacted soil under the trellis which is common in established vineyards. Without some type of tillage, compaction may limit cover crop establishment. Hand hoeing has yielded the best results. One grower advisor tried a Weed Badger. Subsequent seeding of white clover was unsuccessful. While effective for weed control, it is possible that the coarsely tilled soil was not ideal for seeding. Another participant felt the Tournesol Sunflower cultivator did a good job of preparing the under vine area for seeding. The lack of a suitable implement for effective site preparation has hindered expansion of under vine cover crop acreage as hand labor is not available/too expensive for other than a small trial area.

Clover: The impact of clover on vine performance has varied. On one site with heavier soils, it stimulated shoot growth which delayed fruit ripening. In several other vineyards, clover depressed or had no impact on shoot growth. In one newly planted vineyard, young vines benefited from clover as no supplemental N was required. In the cover crop trial, nitrate-N levels (lysimeter samples) have been highest in clover plots. However, this has not translated to increases in shoot growth or vine N status. Clearly the ability of clover to provide N is somewhat unpredictable and is influenced by site, soil and management. Dutch white clover and New Zealand clover have been successfully established in many vineyards. Under drought conditions of the last two summers, both have died back then resumed growth with more frequent rain in the fall. Within the scope of this project (3 seasons), neither white nor New Zealand clover has required re-seeding. On the other hand, according to Björkman, red clover does not persist well and thus would require re-seeding every few years. In two grower cooperator blocks, red clover established well but was 2-3 ft. tall, interfering with the fruit zone (28-36” high) and other vineyard operations. Trials were terminated before a judgment could be made on the need for re-seeding.

Fescue: While slow to establish, the No Mow developed into a thick carpet in most blocks. It grows to about 10” then flops over. Vines in fescue plots were severely water stressed and N deficient during the extended summer droughts, resulting in lower vine pruning weights. Björkman speculated 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 and water stress, particularly in fescue plots. Within the scope of this project, fescue has done a much better job than clover with keeping escape weeds to a minimum.

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. Previous work with subterranean clover (Trifolium subterraneum is the most common species) was unsuccessful as the sub-clover winter killed. Sub-clover is low growing, self-reseeding, becomes dormant in the summer and resumes growth in the fall.

Management: There was frustration with escape weeds getting up into the canopy as fixed fruiting wires range from 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, all very labor intensive. In several blocks, the tractor mounted row middle mower was used to mow close to vine trunks, requiring two passes per row. This is feasible only with a laser planted vineyard; otherwise, damage occurs to protruding trunks. In addition, this practice leaves a ‘weed mohawk’ directly under vines.

Rodents: One block with fescue and clover plots had a significant rodent problem, including damage to trunks. Signs of rodents were evident in the no mow fescue plots of the cover crop trial but there has been no evidence of trunk damage. Dr. Tony Wolf, Virginia Tech, has also been researching permanent cover crops. He feels that maintaining a small weed free zone around trunks with herbicide may help to reduce rodent damage (December 5, 2014 e-mail).

Under trellis mowing trial summary: This trial involves four treatments: T1 – season long mowing (3 times); T2 – glyphosate only (2x, May 30 & July 31); T3- mowing 2x + glyphosate July 1; and T4 – mowing 2x + glyphosate July 31. As in previous years, vine pruning weights were highest in vines maintained with glyphosate; however, there was no statistical difference among treatments. Vine nutrition, as determined by petiole analysis, was similar for all treatments (petiole analysis data not presented). There were no meaningful differences in yield or fruit ripeness at harvest. Water samples collected from lysimeters were analyzed for nitrate-nitrogen on 5 dates. Results suggest that nitrate-N leaching was highest in glyphosate plots compared to other treatments.

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. No mow fescue was slow to establish but filled in plots well. Clover established quickly but there has been a gradual decrease in the percentage of clover cover crop. 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 December 1-2, 2014. Vines in no mow plots (T3) had lower pruning weights than vines in glyphosate and clover plots, T1 & T2, respectively. Petiole nitrogen was lowest in fescue, intermediate in glyphosate and highest in clover plots (petiole analysis data not presented). Vines in clover plots also showed lower levels of phosphorus compared to other treatments. Potassium was lower in both cover crop treatments compared to glyphosate plots. Water samples collected from lysimeters were analyzed for nitrate-nitrogen on 5 dates. Results show that nitrate-N leaching was highest in clover plots compared to other treatments. However, differences were not statistically significant due to high variability in the data.

Additional information and data can be found in the progress report posted on our website: http://ccesuffolk.org/grape-program. [This report will be posted winter, 2015.]

• Under trellis cover crops – shoot length and pruning weights

• Under trellis mowing – treatment dates and percent cover
• Under trellis mowing – shoot length and pruning weights
• Under trellis mowing – harvest data
• Under trellis mowing – lysimeter results
• Under trellis cover crops – percent cover
• Under trellis cover crops – harvest data
• Under trellis cover crops – lysimeter results

Collaborators: