COVER CROPS in South African Vineyards

COVER CROPS IN SOUTH AFRICAN VINEYARDS

In the second strategy, full-surface chemical control was applied at the end of November, to allow the cover crops to set seed, thereby reducing the need to sow every year.As part of a third strategy, the cover crops were controlled chemically during the first week of October, to extend the growing season and thereby increase dry-matter production. Mechanical weed control was applied from just before grapevine bud- break.Where mechanical control is mentioned, it was only used in the work

row.The vine row was still chemically treated. It should be obvious from the above that cover crops are not seen as a stand-alone weed-control solution, but that they form part of an integrated production system. Nonetheless, cover crops ren- der the use of pre-emergence herbicides unneces- sary, and reduce the requirement for post-emer- gence herbicides. Research on the best practices for cover-crop establishment, with the aim of maximising dry- matter production, are discussed in Cover-Crop Establishment in Chapter 4 (p78).

COVER CROPS RENDER THE USE OF PRE- EMERGENCE HERBICIDES UNNECESSARY, AND REDUCE THE REQUIREMENT FOR POST-

EMERGENCE HERBICIDES.

The effects of cover crops on weeds are described in Weed Control in Chapter 5 (p92). Over time, certain weed species adapt to the weed-control method applied, whether these are chemical or biological. Weed Control therefore includes results of studies on the effect of different cover crops, and their management, on weed populations. Knowing the dynamics of a weed population under cover-crop management allows the producer to adapt his weed-control strategies, thereby preventing the problem weeds from becoming dominant over time. Water infiltration, retention and drainage Bare soil disrupts optimal water use in several ways. Firstly, bare soil tends to form an impermeable crust when impacted by water droplets. Although the crust can be broken by mechanical cultivation, it may recur after a single rain or irrigation event.Water is also more likely to run off bare soil.The net result is reduced water infiltration.

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