COVER CROPS in South African Vineyards

CHAPTER 4 COVER-CROP ESTABLISHMENT

4,50

4,00

3,50

3,00

2,50

1996 Sown annually 1996 Self-sown 1998 Sown annually 1998 Self-sown

2,00

1,50

1,00

0,50

Dry matter production in tonnes per hectare

0,00

Paraggio bur

Rye Overberg oats Black oats Grazing vetch

Pink serradella

Woogenellup subterranean

medic

clover

FIGURE 4.2. Dry-matter production of cover crops sown annually compared to re- establishment from self-sown seed in the Lower Orange River region. Adapted from Fourie (2005).

Grazing vetch re-established successfully in 1996. It was then given the opportunity to again reseed and re-establish in 1997. However, the dry- matter production of self-sown grazing vetch was 81% of that of annually sown grazing vetch in 1997, and 63% in 1998.This suggests the need to sow 10 kilogram of seeds per hectare in the second year, and 25 kilogram in the third year, when allowing this plant to self-seed. Dry-matter productionof self-sownParaggioburmedicwas approximately 80% that of the annually sown medic. This indicates that, for this cover crop, seeding density could be reduced to 5 kilograms of seed instead of 25 kilogram of seed per hectare in every second year. The most success was achieved with Woogenellup subterranean clover. Dry-matter production of self-sown Woogenellup subterranean clover was 45% of that of annually sown clover in 1996, and 99% in 1998. Therefore, this plant can re-establish itself in time. The greater success achieved with Woogenellup subterranean clover, Paraggio bur medic, and grazing vetch in this region contrasts with the results in the other regions. This is attributed to the warmer climate and sandier soils that assisted in scarifying the hardened coats of the legume seeds.

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