Investigating annual under-vine cover crops as a sustainable alternative to herbicides in Northeast vineyards

Investigating annual under-vine cover crops as a sustainable alternative to herbicides in Northeast vineyards

Summary

 Grape growers traditionally use herbicides on the vineyard floor, which contributes to resistance, runoff, environmental contamination, and soil degradation. Currently cover crops are generally only grown between rows, while an herbicide strip is maintained directly under grapevines, leaving the bare soil prone to erosion and herbicide leaching. Given the expense of herbicide applications and rising consumer demands for sustainably produced wine, the Northeastern U.S. could greatly benefit from investigating alternative and sustainable vineyard floor management practices. In the Finger Lakes region of New York State, this study compares two annually established cover crops, chicory and buckwheat, planted directly underneath Riesling grapevines, to the conventionally bare soil maintained with glyphosate. How the second year of establishment of under-vine cover crops affect vine vegetative growth, harvest yields, fruit and juice characteristics and wine quality have been examined for the 2013 growing season. This past year, chicory was found to significantly reduce certain measures of vine vegetative growth, including reducing shoot diameter and the number of leaf layers in the canopy and subsequently, cluster light exposure was increased compared to the glyphosate sprayed control. Chicory also reduced the yield per vine and individual cluster weight by 25% in 2013. There were no significant differences detected in predawn and midday stem water potentials, measures of vine water status. Further analysis of the nutrient concentration of vine tissue may illuminate why chicory reduced measures of growth and yield compared to buckwheat and the control. This grant has help enable research to evaluate if two different species of under-vine cover crops – buckwheat and chicory – can be successfully established in the under-vine region and used as an alternative to herbicide in the vineyard.

Objectives/Performance Targets

The objectives for this project as described in the original proposal are as follows:

Objective 1. Evaluate under-vine cover crops as a sustainable alternative to herbicide use in the Finger Lakes, New York cover several growing seasons

2. To determine if annual cover crop species planted in under-vine rows reduce excessive vine vegetative growth and vigor and improve canopy architecture, resulting in improved fruit and wine quality.

3. Evaluate if under-vine cover crops compete with grapevines to alter vine water and nutrient status.

4. To promote sustainable vineyard floor management alternatives like under-vine cover crops in cool and humid climates to researchers and growers.

Accomplishments/Milestones

May – August 2013.  Grapevines dehilled and under-vine cover crops were established for a second year. Measures of vine vegetative growth including shoot length and growth rate, measuring shoot diameter, and canopy growth and light characteristic were taken. Cover crop establishment was quantified by percent coverage and above ground biomass. Midday stem water potentials were taken throughout the season and petioles were collected at vearison and submitted for nutrient analysis.

 Under-vine cover crops successfully emerged and grew their second year of establishment. In this year of the experiment, chicory expressed its biennial growth habit and produced flowering stalks that significantly increased the cover crop biomass for this species in this second year, whereas buckwheat established at similar rates to 2012 (Fig. 1).

Unlike in 2012, significant differences in measures of vegetative growth were found in 2013. Chicory significantly reduced shoot diameter and the number of leaf layers in the canopy. The fewer leaf and shade producing layers resulted in the fruit from vines planted with a chicory under-vine cover crop having much higher cluster exposure flux availability or the cluster exposure to light and a greater percentage of exposed versus shaded clusters compared to the glyphosate sprayed control treatment. Buckwheat was not found to affect measures of vegetative growth for a second year. Shoot tip activity was not able to be rated at veraison this year, due to severe downy mildew infection causing early defoliation, but this was the only planned data measure that was unable to be taken. 

September 1, 2013 – NE SARE funding commenced.

 October 3, 2013 – Research fruit harvest. Yield measurements were taken including the total number of clusters and total weight of fruit per vine. Random cluster samples were taken for each replicate and sampled for berry size and then crushed into juice which has been submitted for analysis. Fruit was sent to the Vinification and Brewing Lab at the New York State Agricultural Research Station for fermentation.

In 2012, there were no under-vine cover crop effects to yield components. In 2013, chicory significantly reduced the yield per vine and average cluster weight by about 25% and individual berry mass and the berries per cluster by 14% compared to the glyphosate control. Buckwheat did not significantly affect yield components (Table 1).

No significant differences were found in measures of vine water status for a second year (Fig 2), so differences in yield cannot be attributed to competition for water. Nutrient analysis results from the 2013 season are still pending, and may provide clarity to explain why chicory reduced vegetative growth and yield.

 In the first year of this experiment, chicory reduced the titratable acidity of juice by 1 g/L compared to the glyphosate control at harvest. Analysis of juice characteristics from 2013 is pending and these results will be critical in understanding the effects of using under-vine cover crops the resulting juice and wine.

Overall, this experiment was conducted successfully for a second year, in the 2013 growing season. This was only the second year of establishment for the under-vine cover crops, so continued evaluation to see if any reduction of vegetative growth or yields is ever seen in the buckwheat and if the trend continues for chicory. The vigorous, biennial growth habit of chicory was unexpected in the under-vine region where there are two intensive cultivation operations every year, but could account for why this treatment has produced significantly different measures of growth and yield compared to the herbicide control and buckwheat. Understanding if there is a consistent effect on juice characteristics will be important. 

• SARE 2013 Report Figures for L. Jordan

Impacts and Contributions/Outcomes

Results were presented at the following two conferences with both researchers and growers present and members of industry and academia expressed continued interest in research evaluating under-vine cover crops.

 June 26^th, 2013 – Results from 2012 selected to be presented at the American Society of Enology and Viticulture conference in Monterey, California in the Poster Flash talk session.

November 19^th, 2013 – Presented at the 2013 Cornell University Recent Advances in Viticulture and Enology conference

Results were also presented at the Department of Horticulture seminar series on November 25^th, 2013.

This research has shown that two different species of under-vine cover crops  – buckwheat and chicory – can be successfully established in the under-vine region and used as an alternative to herbicide in the vineyard. Many industry members could benefit from using chicory which reduced undesirable vegetative vigor and reduced yield which could eliminate the need for costly leaf thinning and crop adjustment passes in the vineyard. For growers that are not looking to alter vine characteristics or yield components, buckwheat could provide an alternative to herbicide. Further evaluation in the upcoming years of successive years of establishment of under-vine cover crops as proposed by this funded project would be vital to make recommendations to growers with confidence. 

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