COVER CROPS in South African Vineyards

COVER CROPS IN SOUTH AFRICAN VINEYARDS

Coastal region Black oats, Paraggio bur medic, and snail medic should preferable be sown in mid-March, while rye, triticale, and Overberg oats should be sown during the first two weeks of April to maximise dry-matter production. Dry-matter production of cover crops sown at different dates is shown inTable 10.3. TABLE 10.3. Effect of sowing date on dry-matter production of different cover crops in the Coastal region as measured at the end of August. Adapted from Fourie et al (2001).

Dry-matter production in tonnes/hectare

Cover crop

Sown 19–22 March Sown 1–9 April

Sown 2–5 May

Rye Triticale Overberg oats Black oats

4.77 4.60 5.69 8.90 6.62 5.09

6.30 5.55 8.88 8.39 4.42 4.70

2.95 3.79 1.90 2.88 4.20 4.48

Paraggio bur medic Kelson snail medic

To help ensure the successful establishment of cover crops, 18 millimetres of water per week is needed during the first eight weeks after the cover crop is sown.The same irrigation can allow oats to produce as much as 8.9 tonnes of dry matter per hectare. However, if full-surface irrigation is not available, the first autumn rains will still allow the producer to sow. Lower Orange River region All cover crops should be sown during the last two weeks of March. In this semi-arid region, the cover crops should receive 18 millimetres of water weekly for the first eight weeks after sowing. Thereafter, 18 millimetres of water should be applied every two weeks until grapevine bud-break. Where the micro-sprinkler irrigation is not capable of wetting the whole of the soil surface in the work row, rye, Paraggio bur medic, and grazing vetch should be sown. Full-surface micro-sprinkler irrigation allows the producer to also consider pink serradella and black oats.

181