COVER CROPS in South African Vineyards

COVER CROPS IN SOUTH AFRICAN VINEYARDS

in integrated and organic production systems were compared to conventional production without a cover crop. The cover crops sowed in this trial were Henog rye and Pallinup oats. Full-surface chemical weed control was applied in the integrated production systems from mid-October, and in the conventional production systems from bud-break. Winter-growing weeds were collected from the work row each year at the end of August.The contributions to total dry-matter production of each winter-growing weed species at the start and end of the trial are shown in Figure 5.29.Wild radish was the dominant weed in all treatments at the start of the trial. Perennial weeds (yellow sorrel, narrow-leaf ribwort, and hairy wild lettuce) increased in the integrated and organic production treatments where cover crops were sown.This was mainly due to an increase in yellow sorrel in the integrated treatment, whereas both yellow sorrel and narrow-leafed ribwort increased in the organic treatment. However, annual weeds remained more common than perennial weeds in all treatments after five years.

100%

90%

80%

Yellow sorrel Narrow-leaf ribwort Hairy wild lettuce Wild radish Broadleaf purple vetch Bur clover Prickly oxtongue Winter grass Other

70%

60%

50%

40%

30%

20%

10%

0%

2000 Conventional Relative perecentage contribution to total dry matter 2005

2000 2005 Organic production

2000 2005 Integrated production

FIGURE 5 .29. Species composition of the dry matter produced by winter-growing weeds in different treatments at Plaisir de Merle in the Coastal region. Adapted from Fourie and Raath (2008).

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