COVER CROPS in South African Vineyards

CHAPTER 5 WEED CONTROL

No cover crop

3,72

Jade canola

0,53

Nemat

0,36

Braco white mustard

0,33

Caliente

0,17

Pallinup oats

0,15

0,00 0,50 1,00 1,50 2,00 2,50 3,00 Dry matter of weeds in tonnes per hectare

3,50 4,00

FIGURE 5.26. Dry-matter production of winter-growing weeds in cover-crop treatments and a control without a cover crop in drip-irrigated vineyards at Blaauwklippen in the Coastal region. Adapted from Fourie et al (2015).

A trial was also conducted in a non-irrigated vineyard at Plaisir de Merle over a period of six years. For the first five years, the cover crop was Henog rye, and for the final year it was Pallinup oats. Cover crops were sown in autumn. The main purpose of the trial was to evaluate organic and integrated soil- management practices. The conventional control received full-surface chemical weed control from bud-break, and the integrated treatment received full-surface chemical weed control from mid-October. The average dry-matter production of winter-growing weeds was 0.28 tonnes per hectare in the presence of cover crops, compared to 1.46 tonnes per hectare in the control. Cover crops therefore significantly reduced the stand of winter-growing weeds in this trial. Summer-growing weeds The effect of cover crops on dry-matter production of summer-growing weeds was assessed in the trials at the ARC Infruitec-Nietvoorbij research farm in Stellenbosch. Full-surface micro-sprinkler irrigation was applied to the vineyards. None of the cover crops produced sufficient dry matter to act as a mulch and suppress summer-growing weeds in the absence of chemical weed control. Full-surface chemical weed control starting just before grapevine

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