COVER CROPS in South African Vineyards

COVER CROPS IN SOUTH AFRICAN VINEYARDS

The success of a cover crop depends on its ability to outcompete winter- growing weeds by either preventing their germination or suppressing their growth.The cover crop must also produce enough dry matter to mulch the soil surface and thereby stop summer-growing weeds from emerging. A cover crop must produce at least 2.5 tonnes of dry matter per hectare to start suppressing weeds. The greater the dry-matter production, the more effective the weed suppression, and therefore the less chemical weed control needed.Although cover crops that produce 2.0 tonnes of dry matter per hectare will not effectively suppress weeds, they will improve water infiltration and reduce soil erosion. The names and seeding densities of the potential cover-crop plants assessed in open-land trials are listed inTable 3.1. Legumes were included to evaluate whether they could supply the nitrogen needed by the grapevines.This aspect is covered more fully in Effect of Cover Crops on Soil Carbon and Minerals in Chapter 7 (p124) and Effect of Cover Crops on Grapevine Nutrition and Performance in Chapter 8 (p140). TABLE 3.1. The seeding density for grasses and legumes evaluated in open-land trials in the Coastal region, Breede River valley, and Olifants River valley. Adapted from Fourie et al (2001) and Fourie et al (2006).

Seeding density in kilogram per hectare

Common name

Scientific name

Grasses Perennial phalaris or bulbous canary-grass

Phalaris aquatica ‘Sirosa’

25

Overberg oats

Avena sativa ‘Overberg’ Avena strigosa ‘Saia’

100 100 100 100 100

Black oats

Barley

Hordeum vulgare

Rye

Secale cereale ‘Henog’ × Triticosecale ‘Usgen 18’

Triticale

Legumes Gabriel perennial lotus Campbell annual lotus Harbinger medic Kelson snail medic

Lotus corniculatus ‘São Gabriel’ Lotus hispidus ‘Campbell’ Medicago littoralis ‘Harbinger’ Medicago scutellata ‘Kelson’

12 10 25 25

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