WINETECH Technical Yearbook 2020

Raise your goblet

2009 Hectares The traditional training of a bush vine involves the upward positioning of bearers to shape four to eight arms in the form of an open cup or goblet. This process takes several years, as cutting bearers too long can result in them bending downwards under the weight of the grapes. The ideal is to achieve an open goblet which allows good distribution of bunches. The arms of older bush vines have normally been developed to a raised form and grapes consequently do not hang close to the soil surface (photo 1). Van Zyl and 2019 Hectares 41569 37097 39347 39073 15012 10338 4830 3307 312 116 259 719 156 74 0 0 0 25 1020 74 101259,49 92066,96 TOTAL HECTARES vine is usually very good and the yield lower, resulting in more full-bodied and concentrated wines. These days a variety of wines can boast the terms bush vine or old bushvine on their labels.

Van Huyssteen (1980) found, during a vineyard trellis trial in Robertson, that temperatures within the canopy, as well as bunch temperatures, were higher in the case of bush vines compared to Perold and lenghtened Perold systems. From veraison to harvest, the bunch temperatures in the bush vine vineyard at 12:00 measured on average 6.73°C higher than in the lengthened Perold vineyard. It was found that the bush vine vineyard’s bunches were more exposed to the sun, but that bunches also received more reflected heat from the soil surface. In cooler areas this extra heat can help to accelerate ripening and lower acidity, but in warm areas higher temperatures during ripening are unwanted.

Hedge Perold Another reason for the move away from bush vine vineyards, is probably the strive towards higher productions made possible by trellis systems’ bigger canopies. The increasing availability of irrigation water has further reinforced this trend. There is also a sharper focus on mechanisation, and the fact that pruning and harvesting processes cannot be mechanised in bush vines, forms part of the considerations when planning to establish a vineyard. The cultivation of vineyards as bush vines remains a good option however in water- scarce areas where the expected growth is low to moderate, and the majority of bush vine vineyards (80% of the total) can still be found in the Swartland, Paarl and Stellenbosch regions (figure 2). At an average cost of R80 000 per hectare for a trellis system, the establishment of a bush vine vineyard is also considerably cheaper. The fact that the arms of a bush vine are not renewed during winter pruning, results in fewer large pruning wounds and bush vines consequently also live longer. Large pruning wounds cause dieback and fungal diseases penetrate the vine through these wounds. The thriving of bush vines under relatively dry conditions has enabled the making of high-quality wines from fertile cultivars like Grenache noir, Cinsaut, Mourvedré, Pinotage and Chenin blanc. The sunlight exposure of bunches within a bush Bush vine Other Lyre system Guyot Staked vine TOTAL

SEPTEMBER 2020

TRELLIS SYSTEM PER DISTRICT 2009 VS 2019

HANNO VAN SCHALKWYK: Vinpro, Paarl KEYWORDS: Trellis systems, bush vine training

Horizontally divided

Vertically divided

Hedge (mechanical pruning)

Very few trellis systems can claim that its existence predates tractors. The bush vine is one of those older systems that can still be seen today, albeit not so widely used anymore. Is it still relevant in the modern era of viticulture? With the introduction of tractors and a greater focus on mechanisation, the use of cordon systems, like the hedge and Perold systems, increased significantly. According to Archer (1991), the use of bush vine vineyards in Stellenbosch has long been declining, with 59% in 1971, 38% in 1979 and 30% in 1987 of vineyards cultivated as bush vine. In the more recent past, the decline in the use of bush vines (30% over the last decade) can be seen in figure 1.

FIGURE 1. Trellis systems – 2009 vs 2019 (SAWIS).

10000 15000 20000 25000 30000 35000 40000 45000

41569

39347

39073

37097

15012

10338

4830

3307

0 5000

1020

719

312

259

156

116

74

74

25

0

0

0

Hedge

Perold

Bush vine

Horizontally divided

Other

Vertically divided Lyre system Guyot

Hedge (mechanical pruning)

Staked vine

2009 Hectares 2019 Hectares FIGURE 1. Trellis systems – 2009 vs 2019 (SAWIS).

WINETECH TECHNICAL YEARBOOK 2020 140