COVER CROPS in South African Vineyards

CHAPTER 8 EFFECT OF COVER CROPS ON GRAPEVINE NUTRITION AND PERFORMANCE

The ratio of grape yield to shoot mass is shown in Figure 8.16. Ratios of less than four, as well as the relatively high shoot mass, indicates that a bigger harvest could have been loaded on the young grapevines in 1995/96. rol

5,00 4,50 4,00 3,50 3,00 2,50 2,00 1,50 1,00 0,50 0,00

1995/96 2002/03

Ratio of grape yield to shoot mass

Sown annually

Sown annually

Sown annually

Sown annually

Sown annually

Sown annually

Sown annually

Sown annually

Sown two-yearly

Sown two-yearly

Sown two-yearly

Paraggio Kelson Woogenellup No Sown two-yearly Sown two-yearly

Sown two-yearly

Sown two-yearly

Sown two-yearly

Chemical control

Henog Overberg Saia black Grazing Faba

oats

oats

vetch bean bur medic snail

rye

clover cover

medic

crop

FIGURE 8.16. Ratio of grape yield to shoot mass in cover-crop treatments compared to a control in the Coastal region. Values below line indicate potential for increased grape yield. Adapted from Fourie et al (2006). A ratio of grape yield to shoot mass ratio of 2.50 in some of the legume treatments demonstrate that these treatments created a luxurious supply of nitrogen during grapevine flowering, resulting in a high nitrogen uptake by the grapevines.This suggests that grasses are preferable to legumes as cover crops in full-bearing grapevines on sandy loam soils in the Coastal region. An alternative option is to control cover crops as late as the first week of October where full-surface irrigation is available. However, in drip- or non- irrigated vineyards the cover crops should be controlled just before grapevine bud-break, to preserve soil moisture for the grapevine-growing season. A study by Van Huyssteen andWeber (1980) looked at grape yields in a non-irrigated vineyard at the ARC Infruitec-Nietvoorbij research farm in Stellenbosch. Barley was the main cover crop.

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