Hemp would be a great plant cover for vines

New research conducted over three years in Marlborough’s Sauvignon Blanc vineyards by winegrower Kristy Harkness and viticulture researcher Dr. Mark Krasnow has revealed that hemp is a viable cover crop, at least as far as New Zealand’s Sauvignon Blanc vineyards are concerned.

Research, as described by the New Zealand Wine Grower, showed that hemp did not compete with grapevines and had a beneficial effect on the soil and the wines. During the country’s dry season, hemp also thrived without additional irrigation when other crops failed to survive, allowing the plants to sequester carbon for a longer period during the season.

Assessment of the Impact of Hemp on Vineyards

To assess the effects of a hemp cover crop and an intercrop on grapevines and vineyard soil, researchers planted industrial hemp seeds amidst the rows of grapevines. The hemp plants demonstrated a superior ability to adapt without additional irrigation, and rather than having a negative effect on the wines, they actually improved their quality compared to grapes that were not grown alongside hemp.

«The hemp plants developed large roots at least 30 cm long and were able to grow in the tractor wheel tracks between the rows, where the root system can mitigate the soil compaction caused by viticultural operations,» the researchers said. «Juice/must samples from the 2019 harvest showed a greater diversity of yeast species from the hemp area than the control, and produced a significantly better wine.»

Vineyards and hemp fields

Mr. Harkness highlighted hemp's ability to benefit both the soil and the wine, calling this discovery «very exciting.».

«The differences in native yeast populations caused by hemp cover crops are a topic of great interest,» said Mr. Harkness. «The suggestion that hemp might improve wine quality is an interesting topic of study, but it’s not a path I’m currently pursuing. As a winemaker, I focus on producing the highest-quality fruit and improving soil health in the vineyards.»

Mr. Krasnow also described the lack of competition between hemp and grapes as «somewhat surprising, given the size of some of the plants.» Although the study did not directly assess this aspect, Mr. Krasnow believes that mixing hemp with other cover crops—such as clover for nitrogen and buckwheat for beneficial insects—offers a huge potential benefit for vineyards. This would not only make it possible to produce better grapes with fewer inputs and to sequester carbon, but also to reduce soil compaction caused by tractor tires, which can be a major problem in vineyard soils.

These results could pave the way for a vineyard where it is not necessary to plant grass and, therefore, not necessary to mow. Instead, a mixture of cover crops could be planted, which would improve grape quality, conserve water, be more bee-friendly, reduce diesel consumption, and increase profitability, according to Mr. Krasnow.

«Mowing doesn’t improve the quality of the wine. It may look nice and neater to people walking by, but it’s not very good for the soil,» he added.

«Given the potential of hemp as a cover crop—in terms of improving vineyard soils, potentially enhancing wine quality, and providing a second source of income for the estate— it is expected that more and more winegrowers will experiment with hemp, either as a cover crop or as part of a more diverse cover crop mix,» the researchers state in the study’s discussion.

«Further research is needed on the effects of wines, both in terms of quality and the potential presence of undesirable cannabinoids and/or aromas in red wines grown near hemp plants.»

The complete study is available here.