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Cover crops are very beneficial to wine grape cultivation. (Photo credit: Johan de Jager).

As wine grape producers will be sowing their cover crops for the upcoming season this month, we uncover the value of using cover crops in vineyards and share tips and findings of cover crop demonstrations from Vinpro’s Gen-Z Vineyard Project.

“The use of cover crops is an extremely valuable practice to ensure healthy soils that help buffer your vines against challenging conditions, including climate change,” said Ivan Jansen van Rensburg, Barenbrug agronomist at a recent Winetech Viticulture Forum meeting.

“Input costs are soaring globally and export wine markets are introducing stricter measures on chemical use in vineyards. Cover crop cultivation provides an alternative solution to weed suppression, nitrogen fixing, microbe stimulation and luring natural predators, while reducing costs and improving yield, quality and profitability,” Ivan says.

“Cover crops offer numerous agro-ecological benefits,” says Emma Carkeek, viticulturist at the Gen-Z Vineyard Project that establishes cover crop demos and a wide range of other viticultural field trials across South Africa’s winegrowing regions.

“Cover crops increase the soil organic carbon over time, aid in soil moisture retention and water infiltration and improve soil stability. They also help limit water run-off and erosion, suppress weeds and increase biodiversity.”

Do’s and don’ts

Ivan shares a few tips for establishing and managing cover crops on vine rows:

Do

  • Plant early under irrigation. This is especially crucial for species such as medics when sown on the grapevine row.
  • Inoculate legumes if the aim is to increase nitrogen levels.
  • Use a mulch to suppress weeds.
  • Plant creeping crops that will cover a larger surface.
  • Spot-spray and “skoffel” weeds.

Don’t

  • Plant twining or tall crops so that they don’t reach the cordon.
  • Apply pre-emergent herbicides that could damage your cover crop.
  • Plant after May.
  • Plant deeper than 1.5cm.

2021 cover crop findings

“Although we already have valuable insights into the use of cover crops in vineyards, it is important to keep learning about the efficiency of different cover crop variations and refining practices under different circumstances in the respective regions,” Emma says.

The Gen-Z Vineyard Project established 11 cover crop field trials from April to May 2021 and hosted five demo days in October last year during which wine grape producers, vineyard managers and viticulturists discussed the findings and shared best practices. The demos were established by Gen-Z, Agricol and Barenbrug, and the grower demo days were hosted by Gen-Z in collaboration with Winetech and Barenbrug.

Attendees at the Gen-Z Grower Demo Day held in October 2021 at Welgevallen Experimental Farm in Stellenbosch.

Some of the general observations will be outlined below, however the detailed data of the cover crop demonstrations are available in an article in the May 2022 edition of WineLand magazine’s Winetech Technical section.

Stellenbosch: Welgevallen Experimental Training Vineyards
Two cover crop mixes and one single varietal (US 2014 triticale) all produced impressive stands and biomass and suppressed weeds effectively. When rolled using a crimp roller, the cover crops created a protective mat over the soil that lasted for several months. The first mix consisted of Barpower forage rye, Haymaker grazing vetch and Scala brown mustard, and the second mix included Moby forage barley, Arvika forage peas and Tajuna fodder radish.

Barsaia oats and Tajuna fodder radish at Kanonkop Wine Estate.

Stellenbosch: Kanonkop Wine Estate
Weed suppression was good in all three cover crop combinations that were sown at this site, however a mix of Barsaia oats and Tajuna fodder radish performed best overall in terms of biomass production, followed by a mix of Barpower forage rye, Haymaker grazing vetch and Scala brown mustard. The combination of Moby forage barley, Stala phacelia and Arvika forage peas produced less biomass, but weed suppression was still very effective.

Paarl: Klipvlei farm
A blend of Moby forage barley, Venice white mustard and Arvika forage peas produced the most biomass, largely due to the successful growth of the forage barley. A mix of Barpower forage rye, Tajuna fodder radish and Azuro bitter lupines was average, while a third combination of Barsaia oats and Haymaker grazing vetch was impeded by high weed pressure and the emergence of cereals from the previous season.

Worcester: Cilmor farm
Promising results across all three plots, with excellent biomass produced and effective weed suppression. A mixture of Barforce silage barley and Moby forage barley grew densely to overshadow weeds, Barpower forage rye and Venice white mustard produced a high biomass and the third combination of Barsaia oats, Tajuna fodder radish and Haymaker grazing vetch showed excellent weed suppression.

Barpower forage rye and Venice white mustard at Cilmor farm.

Breedekloof: Diepkloof farm
Despite the challenge of heavy clay soils, the mixtures at this site produced good biomass overall, in part due to good rainfall in 2021. Barsaia oats and Scala brown mustard outperformed the other two mixes in terms of biomass produced. Weed suppression was very good in both the Barpower forage rye, Haymaker grazing vetch and Venice white mustard mix, as well as the Moby forage barley, Arvika forage peas and Tajuna fodder radish mixture, however the grazing vetch and radish were unsuccessful in the respective mixes.

Robertson: De Wetshof
All three cover crop combinations performed well, and medics sown on the grapevine row shows excellent potential for a grapevine row cover and living mulch. A combination of Barsaia oats, Tajuna fodder radish and Haymaker grazing vetch produced the highest biomass, dominated by the oats, followed closely by Moby forage barley and Stala phacelia. Barpower forage rye and Scala brown mustard had an average to good performance.

Cape South Coast: Paul Cluver Wines

The cool soils in this area make cover crop cultivation a challenge, but three mixtures still showed good growth, biomass production and weed suppression. A mixture of US 2014 triticale, Fiesta faba beans and Stala phacelia produced the most biomass, followed by Barpower forage rye and Haymaker grazing vetch and lastly a mix of Moby forage barley, Arvika forage peas and Tajuna fodder radish.

Medics on the grapevine row at De Wetshof.

For more information contact:

Gen-Z Vineyard Project
Emma Carkeek
E-mail: emma@vinpro.co.za

Barenbrug
Ivan Jansen van Rensburg
E-mail: ijvr@barenbrug.co.za

 

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