COVER CROPS in South African Vineyards

COVER CROPS IN SOUTH AFRICAN VINEYARDS

Dry-matter production and weed suppression were assessed for two years. Results are summarised in Table 3.3. Cover-crop performance differed significantly between years, with much higher dry-matter production in the second than in the first year. Three grasses (black oats, Overberg oats, and rye) and six legumes (faba bean, Parabinga bur medic, Paraggio bur medic, Kelson snail medic, grazing vetch, and Woogenellup subterranean clover) were chosen for inclusion in the long-term vineyard trial.Woogenellup subterranean clover was preferred to pink serradella and grazing vetch due to its more consistent dry-matter production and winter-growing weed suppression. Vineyard trials The cover crops selected during the open-land trials were further evaluated in a vineyard at the ARC Infruitec-Nietvoorbij research farm. Cover crops were sown annually in the work row. Full-surface chemical weed control was applied from just before bud-break until harvest. Cover crops received 18 millimetres of water per week for the first ten weeks after sowing. Further irrigation was not usually necessary, as winter rains normally supplied the requirement of 18 millimetres of water per fortnight. Dry-matter production for the grasses is illustrated in Figure 3.17 and for the legumes in Figure 3.18. In both charts, the dry-matter production of the natural weed stand is presented for comparison.

10,00

9,00

8,00

7,00

Rye Overberg oats Black oats Weeds

6,00

5,00

4,00

3,00

2,00

Dry matter in tonnes per hectare

1,00

0,00 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 Year FIGURE 3.17. Annual dry-matter production of grass cover crops in vineyard trials in the Coastal region. Adapted from Fourie et al (2006).

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