COVER CROPS in South African Vineyards

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COVER CROPS IN SOUTH AFRICAN VINEYARDS

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30

25

20

15

Sultanina Thompson seedless

10

5

Number of export bunches per vine

0

Sown Sown 1995 annually

Sown Sown two- annually yearly Oats

Mechanical Chemical control control No cover crop

Slashed

Grazing vetch

Dwarf fescue

FIGURE 8.20. The number of export bunches per grapevine in cover-crop treatments compared to no cover crop in the Lower Orange River region. Fourie, unpublished data.

Olifants River valley A trial in the Olifants River valley was conducted at the ARC Infruitec- Nietvoorbij research farm near Lutzville in the West Coast District of the Western Cape. Seven cover crops namely, Henog rye, Overberg oats, Saia black oats, Paraggio bur medic, Parabinga bur medic, pink serradella, and grazing vetch, were compared to a control without a cover crop. Unless otherwise stipulated, 14 kilogram of nitrogen per hectare was broadcast during the second week of April, and 42 kilogram of nitrogen per hectare was broadcast in late September. For treatments with grass cover

crops, 28 kilogram per hectare of nitrogen was broadcast at the two-to-four-leaf stages, while the same amount of nitrogen was applied to the vine row in other treatments. The grapevines were in full production from 1995/96 onward. Shoot mass, grape yield, berry mass and volume, and leaf-petiole nitrogen were determined for the vines. Grape juice was analysed, and research wine prepared and evaluated.

NITROGEN FERTILISATION AT GRAPEVINE

BERRY SET IS NOT NECESSARY WHEN NITROGEN MEASURED AS NITRATE IN THE LEAF PETIOLES OF GRAPEVINES EXCEEDS 1 000 MILLIGRAM PER KILOGRAM.

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