COVER CROPS in South African Vineyards

COVER CROPS IN SOUTH AFRICAN VINEYARDS

9,00

8,00

Triticale Rye|faba bean mix Triticale|vetch two-yearly rotation

7,00

6,00

5,00

Triticale|vetch annual rotation Grazing vetch Dwarf fescue Weeds

4,00

3,00

2,00

1,00 Dry matter in tonnes per hectare

0,00 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 Year

FIGURE 3.15. Annual dry-matter production of cover-crop treatments in vineyard trials in the Breede River valley. Adapted from Fourie (2010).

Triticale under drip irrigation The performance of triticale in a drip-irrigated vineyard was compared to triticale in a micro-sprinkler-irrigated vineyard for five consecutive years. Both treatments received 16 millimetres water per week in the first eight weeks after sowing, followed by 16 millimetres every fortnight until the end of August. Rainfall was supplemented with irrigation. Drip irrigation resulted in significantly lower dry-matter production during dryer winters. The best performance of the drip-irrigated triticale occurred in the single winter when rainfall exceeded the recommended amount for cover crops. The conclusion is that winter rainfall in the Breede River valley is not sufficiently reliable to serve as the sole source of water for cover crops. Full- surface micro-sprinkler irrigation should be installed to eliminate this risk of cover-crop failure in this region, and in other regions with a similar climate. Which cover crops were successful? The long-term average dry-matter production of the different treatments are shown in Figure 3.16. The average dry-matter production of the natural weed stand is given for comparison. Based on the long-term vineyard trial, the cover-crop treatments for this region are ranked as follows: 1. Triticale 2. Rye and faba bean mixture

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