COVER CROPS in South African Vineyards

Figure 1.6

COVER CROPS IN SOUTH AFRICAN VINEYARDS

2000

1950

1900 Soil bulk density in kilogram per metre 3 1850 1800 1750 1700 1650 1600

Field water capacity

1550

1500

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Soil water content as percentage mass

FIGURE 1.6. Compaction of a Clovelly soil shown as bulk density resulting from cultivation at different soil-moisture levels. Adapted from Van Huyssteen and Weber (1980).

The result of compaction is that deeper soil layers become nearly inaccessible to the grapevine roots.The root system is restricted, and so the potential for the plant to absorb water and nutrients is also restricted, which ultimately reduces its performance. One of the benefits of cover crops is their ability to counteract compaction. Cover crops protect the surface of the soil from impacts such as traffic and water. How to use this book Most of the chapters have a general introduction, followed by sections that describe research conducted in the different grapevine-growing regions. In most cases, there is information on the Breede River valley, Coastal region, and Olifants River valley, because these were the regions in which the main cover-crop trials were conducted.Where information is available for other regions, such as the Lower Orange River region, this is presented in separate sections.

27