Ivan Jansen van Rensburg of Barenbrug providing feedback at the Diepkloof demo site.
There’s no denying that a good winter cover crop programme can help you effectively control weeds, improve the soil structure and build up beneficial soil nutrients and microbes in your wine grape vineyard. With such a large variety of cover crops available, the Gen-Z Vineyard Project established and assessed a number of cover crop demo sites across the respective wine regions this year to find out what works well under different conditions.
“The demo sites enable us to see which cover crop species are best suited to certain areas and soil types, with a specific focus on effective weed suppression and soil health,” says Francois Viljoen, manager of the Gen-Z Vineyard Project. “We share these insights with wine grape producers, viticulturists and vineyard managers in the respective regions, while also gaining their valuable feedback that will help us refine our recommendations going forward.”
The Gen-Z Vineyard Project established nine cover crop demonstration sites in April and May this year, in collaboration with suppliers Agricol and Barenbrug, and hosted site visits at De Wetshof in Robertson, Diepkloof farm in the Breedekloof region, Stellenbosch University’s Welgevallen experimental farm in Stellenbosch and Goudini Cellar in the Breedekloof region during September and October.
Medics sown on the grapevine row at DeWetshof in Robertson.
The feedback
Due to drier weather during April, better results were achieved where sowing was carried out later than normal, during May. The cereal crops with earlier growth cycles, such as barley and rye, produced excellent biomass and allowed for earlier termination by rolling or mulching, so as not to compete with the vines. “These cover crop species would be especially suited to drier regions,” says Emma Carkeek, Gen-Z viticulturist.
Later growing species such as vetch and oats were slower to develop due to the cold, wet winter conditions, but as the temperatures increased in spring, they produced exceptional biomass. “It is important to note that these species may not work well in areas where water scarcity is a concern, as they may compete with grapevines during the budding stage,” Emma says.
Although the brassicas (radishes, mustards and turnips) generally did not do well when included in mixes – likely due to the small seed size which makes uniform sowing difficult – they performed well when sowed on their own. Mixes that were comprised of cover crop species with similar growth cycles showed good growth.
For coverage on the grapevine row (berm), the medics and medics/clover mixes that were established for the first year at the De Wetshof demo site provided an excellent “living mulch”.
“Although these demo sites give us really valuable insights into what works well in terms of cover crop species, ultimately wine grape producers should take their specific goals, challenges and conditions into account when selecting the cover crops that would fulfil their needs,” Emma says.
About the Gen-Z Vineyard Project
The difference between rolling the cover crop flat (left) and mowing and depositing the cover crop on the berm (right), as demonstrated during the site visit at Welgevallen. The two rows had a very good stand of Triticale.
“Vinpro’s Gen-Z Vineyard Project was established in 2016 as a knowledge transfer project that connects wine growers, viticulturists, suppliers and researchers to the latest practices, technology and vineyard tools by establishing small-scale field demos across South Africa’s wine regions,” Francois says.
The trials include new cultivars and clones, rootstocks, cover crops, trellis systems, pruning systems and viticultural practices in existing commercial vineyard blocks on producers’ farms. “We communicate the findings through technical and popular articles in print and electronic media, as well as site visits during which industry role-players share their insights,” Francois says.
For more information, if you would like to attend a demo site visit, or partner with the Gen-Z Vineyard Project, contact Francois Viljoen at tel 083 309 7627 or e-mail viljoenf@vinpro.co.za.
