COVER CROPS in South African Vineyards

COVER CROPS IN SOUTH AFRICAN VINEYARDS

The trials described below examined how much water was needed to ripen the harvest of vineyards in the Coastal region, Breede River valley, and Olifants River valley. During the grapevine-growing season (September to February) full-surface micro-sprinkler irrigation was applied to replenish the soil to field-water capacity when approximately 60% of the plant-available water was depleted. In general, the results showed that establishing a winter-growing annual grass or legume in April, and controlling it chemically at grapevine bud- break, reduced the irrigation requirement, irrespective of the soil or region. Coastal region A trial in the Coastal region was conducted over six years at the ARC Infruitec-Nietvoorbij research farm in Stellenbosch in theWestern Cape.The site had sandy loam soils. Cover crops were sown in autumn. Rainfall was supplemented with irrigation for the first ten weeks after sowing.Thereafter, the cover crops were totally dependent on winter rainfall. The vineyard required an average of 231 millimetres of water per hectare per year when no cover crop was present.When rye, oats, or Paraggio bur medic was sown annually, and chemical control started just before bud-

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Irrigation water supplied in millimetres

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Sown Sown two- yearly annually

Sown Sown two- yearly annually

Sown Sown two- yearly annually

Chemical

Mechanical

control

control

Saia black oats

Paraggio bur medic

No cover crop

Henog rye

FIGURE 6.1. The amount of irrigation water per hectare per annum required in vineyards with and without cover crops under full-surface micro-sprinkler irrigation in the Coastal region. Adapted from Fourie (2015).

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