By Kathryn Carter, Anne Verhallen, Dr. Tejendra Chapagain, OMAFRA
Under-vine covers crops are an alternative to the use of herbicides or cultivation in managing weeds in vineyards. Research in other grape growing regions (e.g., New York, Australia British Columbia and Virginia) have shown that annual and perennial cover crops can be effective in managing weeds, controlling vine vigour and improving soil health (Abad et al., 2021).
Under-vine cover crops research is still relatively new, and performance of the cover crops will vary considerably in different growing regions, due to different soil types, and environmental conditions. Cover crops that work in other grape growing areas (e.g., New York, Australia or British Columbia) may not be a viable alternative in Ontario vineyards. In order to be viable in commercial vineyards, under-vine cover crops must establish easily and effectively manage weeds, while having minimal negative impact on yields and fruit quality.
Under-vine cover crops vary in their impact on vine size, with deep rooted cover crops like chicory (Cichorium intybus) and annual ryegrass (Lolium multiflorum) resulting in reduced vine size, while others (buckwheat – Fagopyrum esculentum, rosette forming turnip – Brassica napus) have no impact on vine vigour. As a result, vigour management will need to be taken into consideration when selecting cover crops.
OMAFRA initiated a trial in 2021 with an objective of evaluating the potential of using under-vine cover crops in Ontario vineyards to supress weed growth. The project focused on evaluating a variety of under-vine cover crop treatments that have shown promise in other grape growing regions (e.g., New York, Virginia and British Columbia) to determine their impact on weed management, vine growth, yields and fruit quality. In addition, a screening trial was set up to evaluate several species that are commonly used as cover crops in other commodities to determine their potential fit as under-vine cover crops. For the purpose of this trial, the cover crops selected were those that had minimal impact on vine vigour in other trials.
The trials were set up in a mature organic Reisling block in Beamsville Ontario. A split plot trial with 5 treatments and 4 replications was set up to evaluate a variety of cover crop treatments including buckwheat, buckwheat+phacelia (Phacelia tanacetifolia), rosette forming turnip, natural vegetation/weeds and cultivation/grower standard for organic) to examine their impact on weed pressure, vine growth, vine nutrients, and soil moisture. In addition, smaller screening trials (1 panel plots) were set up to evaluate cover crops that have been used effectively in other commodities to determine their potential for use as under vine cover crops in vineyard including: Subterranean clover (Trifolium subterraneum), Buckwheat and phacelia broadcast, Buckwheat broadcast, Turnip broadcast, Mix, flax (Linum usitatissimum), Common vetch (Vicia sativa), Chickling vetch (Lathyrus sativus), Double cut clover (Trifolium pratense), Crimson clover (Trifolium incarnatum), Balansa clover (Trifolium michelianum), Fodder rape (Brassica napus).
The buckwheat cover crop treatment had the best establishment, and least amount of weeds (Figure 1). The combination of buckwheat + phacelia performed relatively well, but the phacelia didn’t establish as anticipated. In addition, the buckwheat in both treatments grew taller than expected, and had to be cut down to prevent it from growing into the fruiting zone where it could reduce air circulation resulting in increased disease pressure. Rosette forming turnip had poor establishment overall and did not provide adequate control of the weeds. Both the phacelia and buckwheat have attractive flowers and were actively visited by bees.
Soil and Plant Tissue Nutrition
Soil samples were taken prior to seeding cover crops, and this data will be used to monitor the long-term impact of cover corps on soil nutrition. The pre-trial soil report indicated that fertility levels were consistent across treatments. Tissue analysis in all of the under-vine treatments indicated acceptable levels of nutrients indicating that cover crop treatments did not affect petiole tissue nutrition. However Phosphorous, Zinc, and Iron levels were slightly higher in plots with buckwheat and natural vegetation.
Vine Growth and Yields
There were no significant differences in shoot length between the various treatments indicating under-vine cover crops had minimal impact on vine growth (Figure 2).
There were no significant differences between yield in the various under-vine treatments (Figure 3), indicating that the growth of the under-vine cover crops vine didn’t have a negative impact on yields. However, in 2021 precipitation was not limiting. Further work is needed to evaluate performance under varying growing conditions.
Also, quality parameters (e.g., number of cluster per vine, yield, brix, pH, and titratable acidity) were not significantly affected by cover crop treatments.
Conclusion and Future Work
The findings of this trial were similar to what other researchers (e.g., Vanden Heuval, 2017) found indicating that under-vine cover crops can be used effectively to manage weeds without having a negative impact on vine growth or fruit composition.
Although the buckwheat treatments established well and were able to provide adequate weed control, they grew up into the fruiting zone which could create an issue in commercial vineyards and requiring mowing. Researchers from British Columbia had similar issues, while trials in New York, did not have an issue with Buckwheat growing into the fruiting zone. This demonstrates that selection of under-vine cover crops will need to be region/vineyard specific and may vary between sites. Rosette forming turnip did not establish well enough to provide adequate weed management in 2021. A different approach to seeding and establishment may be required for future plantings.
In screening trials, fodder rape, chickling vetch and crimson clover performed extremely well and we hope to include these in future under-vine cover crop trials.
OMAFRA has received funding from the Ontario Grape and Wine Research Institute (OGWRI) to continue researching the potential use of under-vine cover crops in vineyards in 2022. An application has also been made to obtain funding for a three-year project evaluating the long-term use of under-vine cover crops. In addition, research needs to be conducted to find an economically feasible method of seeding the under-vine cover crops.
We are grateful for the funding from Hort Crops Ontario that supported this research. In addition, we are grateful to Dr. Justine Vanden Heuval (Cornell) and Wade Stark (30 Bench Vineyards) for their support.
Abad, J., I. Hermoso de Mendoza, D. Marin, L. Orcaray and L. Santesteban. 2021. Cover crops in viticulture. A systematic review (1): Implications on soil characteristics and biodiversity in vineyard. Oeno one.
Karl, A. 2015. Impact of under-vine management on vine growth, yield, fruit composition and wine sensory analyses of Cabernet franc. MS Thesis, Cornell Univ., Ithaca, NY.
Vanden Heuval, J. 2017. Adopting Under-Vine Cover Crops in Vinifera Vineyards. Research Focus 2017-1.pdf (cornell.edu).
Wise, A. and H. Walter Peterson. 2018. Expanding the Use of Under-Vine Cover Crops in New York Vineyards (cornell.edu).