COVER CROPS in South African Vineyards

CHAPTER 4 COVER-CROP ESTABLISHMENT

In 1997, after five years of establishment, none of the self-sown cover crops produced as much dry matter as those sown annually. Dry-matter production of self-sown rye was 34% of annually sown rye; self-sown black oats was 25%; Parabinga bur medic was 59%; Paraggio bur medic was 35% and grazing vetch was 61%. Trials were extended for the bur medic and grazing vetch. In 1999, the stand of self-sown Parabinga bur medic was 78% of annually sown Parabinga bur medic; Paraggio bur medic was 30%; and self-sown grazing vetch was 37%. Seeds from the various treatments were collected and germinated to determine the number of viable seeds produced by the cover crops. Grazing vetch was the only cover crop that produced more viable seeds than the number used for annual sowing. However, this did not result in higher dry- matter production of grazing vetch in 1997, as was expected.The reason is not known. Grazing vetch grew poorly in 1997 and 1998, and suffered seed damage and predation, which may have contributed to poor dry-matter production in self-sown grazing vetch in 1999. Although the number of viable seeds of the bur medics increased from 1995–1999, it did not reach the density at which these cover crops were being sown.This indicated that neither plant can re-establish successfully.

CERTAIN LEGUMES CAN BE SOWN AT A REDUCED DENSITY IF THEY ARE ALLOWED TO PRODUCE SEEDS IN THE PREVIOUS SEASON.

Based on these results, grazing vetch, and Parabinga and Paraggio bur medic can be sown at a reduced density of 30 kilograms per hectare and 15 kilograms per hectare, respectively, in alternate years, if they are allowed to produce seeds in the previous season. Reference list

Fourie JC, Louw PJE and Agenbag GA. 2005. Cover crop management in a Sauvignon blanc/Ramsey vineyard in the semi-arid Olifants River valley, South Africa. 1. Effect of management practices on selected grass and broad- leaf species. South African Journal of Enology and Viticulture , 26(2), 131–139.

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