COVER CROPS in South African Vineyards

COVER CROPS IN SOUTH AFRICAN VINEYARDS

Soil nitrogen levels after harvest were noticeably lower in the tenth season than in the third season, except for the treatment in which grazing vetch was sown every second year.

Overall, these results from the Breede River valley are consistent with the findings in other regions, in that soil nitrogen levels tend to be higher in annual cover-crop treatments than in a control without a cover crop. Soil nitrogen levels were lower when perennial dwarf fescue was established, than when no cover crop was grown.This suggests that a perennial cover crop can consume nitrogen, thereby potentially competing with grapevines. st mber otation ion August November

SOIL NITROGEN LEVELS TEND TO BE HIGHER IN ANNUAL COVER-CROP TREATMENTS THAN IN A CONTROL WITHOUT A COVER CROP.

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Triticale weed control August Triticale weed control November Rye|faba bean mix Triticale|vetch two-yearly rotation Triticale|vetch annual rotation Grazing vetch weed control August Grazing vetch weed control November Perennial dwarf fescue No cover crop

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5,00 Nitrogen in milligram per kilogram soil

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1995/1996 Third season

2002/2003 Tenth season

FIGURE 7.4. Soil nitrogen measured after harvest in the 0–600-millimetre soil layer in cover-crop treatments compared to a control in the Breede River valley. Adapted from Fourie (2012). Other minerals Soil was analysed for phosphates, potassium, and exchangeable cations in 2000 and 2003. In general, although significant differences occurred between certain treatments, no trends were observed. Potassium concentrations in all the treatments were approximately two to five times the norm for wine grapes.

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