COVER CROPS in South African Vineyards

CHAPTER 5 WEED CONTROL

The average annual dry-matter production of winter-growing weeds in the different grass cover-crop treatments is illustrated in Figure 5.36. It can be seen that the average winter-weed stand in treatments in which a cover crop was sown annually was significantly reduced compared to the control, as well as to treatments where the cover crop was sown every second year. ally.

(2005)

3,00

2,50

2,00

No cover crop Henog rye. Sown annually. Henog rye. Sown two-yearly. Overberg oats. Sown annually. Overberg oats. Sown two-yearly. Saia black oats. Sown annually. Saia black oats. Sown two-yearly.

1,50

1,00

0,50

0,00

1995

1996

1997

1998

.

.

Year

Dry-matter production of weeds in tonnes per hectare FIGURE 5.36. Dry-matter production of winter-growing weeds in grass cover-crop treat - ments compared to a control without a cover crop in the Lower Orange River region. Adapted from Fourie (2005). The average dry-matter production of winter-growing weeds in the different legume cover-crop treatments is illustrated in Figure 5.37.The legumes also gave significant weed-suppression when sown annually, compared to the control, and compared to the treatments where legumes were sown every two years. In addition to the annual cover crops discussed above, this trial included perennial dwarf fescue, which was sown every five years, and slashed regularly. Full-surface chemical weed control was not applied to the fescue. Although fescue did reduce the weed stand, it became infested with common couch. Application of herbicides was eventually necessary, which led to destruction of the cover crop, as can be seen in Figure 5.38. Reference list Fourie JC. 2005. Cover crop management in the vineyards of the Lower Orange River region, South Africa: 1. Performance of grass and broadleaf species. South African Journal of Enology and Viticulture , 26(2), 140–146.

116