COVER CROPS in South African Vineyards

CHAPTER 3 COVER-CROP SELECTION

The cover crops were sown annually.They received 18 millimetres of water per week for the first ten weeks after sowing, and 18 millimetres every two weeks thereafter. Rainfall was supplemented by full-surface sprinkler irrigation. Dry-matter production and weed suppression were assessed for two years. Results are summarised in Table 3.2. All the annual grasses except barley produced more than 5.0 tonnes of dry matter per hectare, and restricted winter-growing weeds to less than 0.4 tonnes per hectare. Grazing vetch, Parabinga bur medic, Paraggio bur medic, and pink serradella all produced more than 4.0 tonnes of dry matter per hectare, which is sufficient to outcompete winter-growing weeds in this region, as well as to supply a weed-suppressing mulch for the grapevine-growing season. Legumes performed better when sown in March, allowing them to maximise dry- matter production before the onset of cold weather in June. Two grasses (triticale and rye) and two legumes (grazing vetch and faba bean) were chosen for inclusion in the long-term vineyard trial. However, grasses such as Overberg oats and black oats, as well as legumes such as Paraggio bur medic could also be considered as cover crops in this region, as they are able to suppress winter-growing weeds, as well as produce enough dry matter to create an effective summer mulch.

JOHAN FOURIE

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