COVER CROPS in South African Vineyards

COVER CROPS IN SOUTH AFRICAN VINEYARDS

These results demonstrate that annual cover crops can increase organic carbon in the 0–300-millimetre soil layer of a sandy loam soil. Nitrogen in the soil Nitrogen was applied at 14 kilogram per hectare during the first week of March, when cover crops were sown, and at 14 kilogram per hectare when they reached the two-to-four-leaf stages. Soil nitrogen levels were measured in the work row at grapevine full bloom, at véraison, and again after harvest. Figure 7.2 shows the soil nitrogen levels at grapevine full bloom. Unless specified, cover crops were sown annually, and weed control started at grapevine bud-break. In the third season, soil nitrogen levels were higher in all the cover- crop treatments than in the control, except in the case of dwarf fescue. Nitrogen was especially high in the treatment where grazing vetch was sown every second year, mostly due to high amounts in the 0–150-millimetre soil level. By the tenth season, soil nitrogen levels had increased for all treatments, as well as for the control, and the difference between the cover-crop treatments and the control was less marked. However, the treatment where grazing vetch was sown every second year still stood out. st mber otation ion August November

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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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Nitrogen in milligram per kilogram soil

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1995/1996 Third season

2002/2003 Tenth season

FIGURE 7.2. Soil nitrogen measured at grapevine full bloom in the 0–600-millimetre soil layer in cover-crop treatments compared to a control in the Breede River valley. Adapted from Fourie (2012).

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