COVER CROPS in South African Vineyards

COVER CROPS IN SOUTH AFRICAN VINEYARDS

TABLE 2.1. Average mean daily temperature and monthly rainfall for Robertson for March 1991 to February 1993. Data supplied by the ARC Institute for Soil, Climate and Water.

Average total monthly rainfall in millimetres

Average mean daily temperature in °C

Month

January February

1.3

23.7 23.6 22.3 18.8 15.6 12.3 12.2 11.9 15.0 17.4 20.3 22.5

21.7

March

7.6

April May June

18.0 19.3 52.1 50.9

July

August

8.6

September

13.8 39.3

October

November December

8.3 3.2

Average total annual rainfall 243.8 The Breede River valley represents a relatively warm and dry grapevine- growing region. However, winters tend to be colder than either the Coastal region or the Olifants River valley. Soil types The soil at the trial site was a medium-textured, sandy clay loam. Clay content was 25% at 0–300 millimetres and 27% at 300–600 millimetres. Irrigation practices Irrigation is required to cultivate grapevines in this region. During the grape- vine-growing season (September to February) full-surface micro-sprinkler irrigation was applied when approximately 60% of the plant-available water was depleted to replenish the soil to field water capacity. Winter rainfall in this region is insufficient for growing cover crops during most seasons. Irregular rainfall with dry intervals necessitated full-surface sprinkler or micro-sprinkler irrigation to provide the water needs of the cover crops. Drip irrigation alone led to disappointing performance of cover crops in dry winters.

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