WINETECH Technical Yearbook 2021

Figure 4

100 150 200 250 300 350 400

-0.2 2020-10-01 2020-10-15 2020-10-29 2020-11-12 2020-11-26 2020-12-10 2020-12-24 2021-01-07 2021-01-21

25 Aug: 0 mm difference

18 Dec: 30 mm drier

13 Jan: 58 mm drier

12 Nov: 0 mm difference

Red cultivars White cultivars

(None)

-0.4

-0.6

(Low)

-0.8

-1.0

(Moderate)

-1.2

Vine row ( under plasti c ) Work row

-1.4

(High)

Soil water content (mm/1.5 m)

-1.6

0 50

(Very high)

-1.8 Leaf stem water potential (MPa)

2020-08-15 2020-09-14 2020-10-14 2020-11-13 2020-12-13 2021-01-12

-2.0

FIGURE 4. Progression of soil water content on the vine row, as well as in the work row, during 2020/21.

FIGURE 5. Progression of midday stem water potential during 2020/21.

VITICULTURAL ASPECTS In 2019/20, the vines were divided to develop one cordon to both sides on the cordon wire, and where possible, four spurs were allowed on a side during pruning. For the first harvest in 2020/21, the crop load of the third-leaf vines was limited to one bunch per shoot. The crop load could possibly be adjusted in the fourth growing season according to the vigour. PLANT WATER STATUS Stem water potential was measured at mid- day with a pressure bomb. In the 2021/21

withdrawal on the vine row increased as the vines were developed and the canopies grew larger over the first three seasons (figure 3). As the rainfall decreased in the summer, the soil water content under the plastic mulch was however consistently higher than in the work row (figure 4). This difference shows the importance of a mulch to conserve soil water for when it is required later in the growing season. A plastic mulch is therefore critically important during the establishment phase, especially in the case of dryland vineyards.

season, the white cultivars generally expe- rienced more water stress in comparison to the red cultivars (figure 5). By mid-January, the red cultivars experienced moderate stress compared to the high stress in the white cultivars. According to the seasonal soil water in figure 3, there was more water available before very high water stress, i.e. <-1.6 MPa, would set in. VEGETATIVE GROWTH Cane masses were measured in August during pruning. A comparison between the first two seasons’ cane mass during pruning

indicated that certain cultivars grew stronger than others in the first two years (figure 6). Chardonnay grew well in the first year, but showed significantly weaker growth in the second year. In contrast, Arinarnoa and Tempranillo tended to grow relatively stronger in the second year than the first. Visual observation indicated very vigorous growth for some of the cultivars in the 2020/21 season. This was especially noticeable lower down against the slope where the soil is better. A higher crop load in the next season could possibly restrict the vegetative growth of these cultivars.

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