COVER CROPS in South African Vineyards

CHAPTER 8 EFFECT OF COVER CROPS ON GRAPEVINE NUTRITION AND PERFORMANCE

Bunch damage A heat wave presented the opportunity to study the effect of different cover crops on the percentage of bunches damaged during véraison. The results are shown in Figure 8.19. Damage was significantly more prevalent in the dwarf-fescue treatment, and where chemical weed control was practiced in the absence of a cover crop. These results demonstrate the value of cover crops and their mulches in protecting grapevines from extreme temperature events. trol rol

50 45 40 35 30 25 20 15 10

5 0 Sown Sown 1995 Sown Sown two- Mechanical Chemical Percentage bunch damage

Slashed

annually

annually yearly

control

control

Grazing vetch

Oats

No cover crop

Dwarf fescue

FIGURE 8 .19. The percentage of damaged bunches in cover-crop treatments compared to no cover crop during a heat wave in the Lower Orange River region. Fourie, unpublished data. Grape yield and quality The number of export-quality bunches per grapevine is shown in Figure 8.20. Although the vines in the treatment with annually sown grazing vetch produced the most bunches, the treatment with annually sown Overberg oats had the highest number of bunches that qualified forThompson seedless. These numbers suggest that cover crops such as Overberg oats can significantly increase the yield of high-value grapes. Reference list Conradie WJ. 1994. Vineyard Fertilisation. Proceedings of a workshop on fertilization, Nietvoorbij, 30 September,ARC Infruitec-Nietvoorbij, Private Bag X5026, Stellenbosch, 7599.

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