COVER CROPS in South African Vineyards

CHAPTER 3 COVER-CROP SELECTION

Vineyard trials The two selected annual grasses (rye and triticale) and legumes (grazing vetch and faba bean) were evaluated in a vineyard.The treatments were: • Triticale monoculture • Grazing vetch monoculture • Triticale and grazing vetch monocultures rotated every year • Triticale and grazing vetch monocultures rotated every two years Each cover crop was sown annually in the work row, except for perennial dwarf fescue ( Festuca arundinacea ‘Cochise’) which was sown every five years. Full-surface chemical weed control was applied from just before bud- break until harvest, except in the fescue treatment. The fescue was slashed from grapevine bud-break, and continued to grow throughout the grapevine- growing season. Cover crops received 16 millimetres of water per week for the first eight weeks after sowing, and 16 millimetres every two weeks thereafter until the end of August. Rainfall was supplemented by full-surface micro-sprinkler irrigation. The annual dry-matter production of the various treatments is illustrated in Figure 3.15. It can be seen that the dry-matter production of the rye- faba-bean mixture did not decline over time. Dry-matter production of the grazing-vetch monoculture declined from the fourth season onward, and in the triticale monoculture from the tenth season onward. In the treatments where triticale and grazing vetch were rotated, annual dry-matter production fluctuated according to which was sown in a particular year.Triticale generally produces more dry matter than grazing vetch. Although the continuous use of triticale by itself gave the best overall dry- matter production, it is recommended that grasses and legumes should be rotated to help prevent the build-up of soil-borne diseases that may target a specific cover crop. The mixture of rye and faba bean also gave good results, but mixtures restrict the rotation options available to producers over the medium to long term. • Rye and faba bean mixture • Dwarf fescue monoculture.

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