COVER CROPS in South African Vineyards
COVER CROPS IN SOUTH AFRICAN VINEYARDS
Relatively high nitrogen uptake by the grapevines caused luxurious vegetative growth in some of the legume treatments. These results suggest that a legume cover crop should not be used every year on sandy loam soils, as it may lead to excessive vegetative growth of the grapevines. Figure 8.12 shows the nitrogen concentrations in the grape juice of vines in the different grass cover-crop treatments, and Figure 8.13 shows the nitrogen concentrations in the different legume cover-crop treatments.
A LEGUME COVER CROP SHOULD NOT
BE USED EVERY YEAR ON SANDY LOAM SOILS, AS IT MAY LEAD TO EXCESSIVE VEGETATIVE GROWTH OF THE GRAPEVINES.
Nitrogen concentration in grape juice in some of the legume treatments exceeded 1 000 milligram per litre, which could affect wine quality. These results suggest that Paraggio bur medic andWoogenellup subterranean clover should not be sown every year on these sandy loam soils. rol
700
600
500
400
1994–1999 2000/01 2001/02
300
200
100 Nitrogen in milligram per litre
0
Sown Sown two-
Sown Sown two-
Sown Sown two- Chemical
annually
yearly
annually
yearly
annually
yearly
control
Henog rye
Overberg oats
Saia black oats
No cover crop
FIGURE 8.12. Nitrogen measured in the grape juice from vines in grass cover-crop treatments compared to a control in the Coastal region. Adapted from Fourie et al (2006).
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