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. This report presents data from the 2013 growing season which was not available at the time of the last report, as well as data for the 2014 growing season (the third year of the experiment). Chicory as an under-vine cover crop reduced vine size greatly compared to the conventional herbicide treatment – from a 5% reduction in pruning weight in year one of the study, to 28% in year two, and then 55% in year three. This reduction in vine size is too great to be sustainable. By the third year of the study using buckwheat as an under-vine cover crop reduced vine size by only 18% compared to the control. Shoot lengths were reduced by the under-vine cover crop treatments. Measured soil physical and chemical characteristics remained unchanged by the use of cover crops by the end of the second year of the study. This grant has help enable research to evaluate if two different species of under-vine cover crops 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:

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

1. 1. 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.

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

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

Accomplishments/Milestones

April 2014. Data on soil physical and chemical characteristics from late 2013 samples received from CNAL, and analyzed. Data presented in Tables 1 and 2. Surprisingly there were no significant differences in soil characteristics as a function of under-vine management.

May – August 2014. Grapevines dehilled and buckwheat as an under-vine cover crop were established for a third year. However chicory – expressing its biennial growth habit – had developed into a full stand with 100% coverage quickly after de-hilling, so was not seeded again. Chicory grew tall and into the fruiting zone, requiring mowing (Fig. 1). In subsequent studies we will use dwarf chicory to prevent the need for mowing. Shoot lengths and growth rates were collected. As in 2013, significant differences in measures of vegetative growth were found in 2014. Chicory and buckwheat significantly reduced shoot length and shoot growth rate (Fig. 2) compared to the glyphosate control.  

October 2014 – 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. 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 3) including pruning weight. In 2014, chicory reduced yield per vine by 22% while buckwheat reduced yield by 11% compared to the control, however the big impact was on vine size as reflected by pruning weight. Pruning weight was reduced in chicory by 55% but in buckwheat by only 18% compared to the control.

Data on fruit composition is not yet available for 2014.

2014 was the third year of establishment for the under-vine cover crops. Although data collection will continue for a fourth year under graduate student Adam Karl, it can be concluded at this point that chicory is likely too vigorous a competitor for Riesling grapevines. In the three years of study buckwheat as an under-vine cover crop is only a moderate competitor and may be a good replacement for herbicide strips in vigorous vineyards. Understanding if there is a consistent effect on juice characteristics will be important (data pending).

• Annual Report Tables and Figures

Impacts and Contributions/Outcomes

Results were presented at the Business, Enology, and Viticulture (BEV – NY) conference in Rochester, NY in February 2014, to approximately 210 grape growers. We demonstrated that buckwheat and chicory can be successfully established in the under-vine region and used as an alternative to herbicide in the vineyard. Some 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, however its use would likely need to be short-term so that vine size wasn’t too diminished. For growers that are not looking to alter vine characteristics or yield components, buckwheat could provide an alternative to herbicide. The fourth and last year of evaluation of these cover crops will help shape more definitive recommendations for the growing community.

Collaborators: