Cover crops are a tool that is growing rapidly in popularity, both in New Zealand and globally. Cover crops are annual and perennial plants that are grown primarily for improving soil health, fixing nitrogen, nutrient cycling, weed management, soil borne disease management, pest management etc.
Video description: For the Holdaways, cover crops species are selected across different functional groups and traits to increase diversity.
Video description: The team at Greystone Wines make extensive use of cover crops to improve soil health and nutrient cycling.
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More on diverse vineyard cover crops
Cover crops tick many of the regenerative principles by keeping soil covered, having diverse living plants feeding soil microbes, and allowing livestock to be integrated into the system if/when grazing the cover crops. In viticulture systems cover crops can help reduce compaction, reduce the need for fertilisers, improve water infiltration and reduce pest and disease pressure. Check out how Greystone Wines and the Holdaways are integrating cover crops below.
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Holdaway vineyard: Cover crop species selection
The Holdaways have been extensively cover cropping since 2018, starting with every second row to ensure there was a row clear for tractors to drive down.
Cover crops species are selected across different functional groups and traits and are direct drilled following a herbicide, which is preferred over cultivation.
After five years of cover cropping Richard is confident he can see better and deeper soil structure than before they started. The increased diversity and abundance of insects in the vineyard has also seen pests such as mealy bug and leaf roller caterpillar populations generally kept to low levels.
Cover crop implementation:
Richard and Robbie try to select plants with traits that are not competitive with vines (such as big fibrous grass roots) and work to a $250/ha seed cost budget.
The focus is primarily on legumes, brassicas and herbs. Grasses and chenopods (i.e. fathen) are already present in the seed bank.
For summer mixes the emphasis is on flowers to host beneficial insects including those that predate insect pests - species include borage, vetch, radish, mustard and even poppies and calendulas.
Mixes have exceed 40 species in some cases.
Tall cover crops can increase the humidity around the grape bunches so this needs to be managed carefully.
Cover crops are either roller crimped, side-throw mulched (to cover the under vine area) or mown.
Greystone Wines: Improving cover crop establishment
The team at Greystone Wines began extensively cover cropping in 2020.
Attempts to direct drill cover crops into existing pasture largely failed due to the presence of a thick browntop thatch that prevented seedling establishment. Cover crops sown following the cultivation of new vine blocks established much better.
The team are now biting the bullet and cultivating every second row of the vineyard to ensure good cover crop establishment, with the hope that cultivation will only be required every 10 or so years.
Cover crop implementation:
Historically cover crops were low diversity and focused on flowering plants to attract beneficial insects to manage insect pests such as leaf roll caterpillar and mealy bug (i.e. phacelia, buckwheat, alyssum)
Now cover crops have a broader intention of also improving soil structure and nutrient cycling and have 16-30 species including species from all functional groups (grasses, legumes, forbs/herbs, brassicas, chenopods).
“We’re just trying to get that diversity in plant growth. The diversity in carbon going into the soil to help this soil have really good water infiltration, oxygen exchange, nutrient availability, all that sort of stuff.”
Nick Gill, Greystone Wines
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