COVER CROPS in South African Vineyards

CHAPTER 10 PRACTICAL GUIDELINES

Cover crops must be sown in every row. When cover crops are grown in every second row, weeds proliferate in the open rows during winter and summer. These weeds serve to maintain the seedbank in the top 50 millimetres of the soil, whereas sowing cover crops in every row allows for the progressive down-management of weed seeds. Sowing dates and irrigation Breede River valley

COVER CROPS MUST BE SOWN IN EVERY ROW.

Paraggio bur medic should preferably be sown in the last week of March, whereas triticale, black oats, Overberg oats, and grazing vetch produce the most fibre if sown during the second week of April. Rye can be sown from the second week of April to the first week of May. Dry-matter production of cover crops sown at different dates is shown inTable 10.2. TABLE 10.2. Effect of sowing date on dry-matter production of different cover crops in the Breede River valley as measured at the end of August. Adapted from Fourie et al (2006).

Dry-matter production in tonnes/hectare

Cover crop

Sown 23–26 March Sown 7–12 April

Sown 1–7 May

Rye Triticale Overberg oats Black oats Paraggio bur medic Grazing vetch

5.19 5.06 4.99 4.39 5.67 4.56

6.18 8.35 7.07 6.81 2.86 6.32

6.43 7.40 6.04 6.09 1.61 3.90

Due to the erratic winter rainfall in this region, irrigation should be applied when necessary to ensure that cover crops receive a total of at least 18 millimetres of water from either rainfall or irrigation per week for the first eight weeks after sowing. Thereafter, the cover crops should receive a total of 18 millimetres of water from either rainfall or irrigation every two weeks until grapevine bud-break.

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