COVER CROPS in South African Vineyards

COVER CROPS IN SOUTH AFRICAN VINEYARDS

Soil types The trial site had a sandy soil. Sand content was 99% at 0–300 millimetres and at 300–600 millimetres, and clay was absent throughout. Irrigation practices The Olifants River valley combines low annual rainfall with relatively high temperatures between autumn and spring, and is frequently burdened with water restrictions.Agriculture in the region relies on irrigation. During the grapevine-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. Cover crops can only be cultivated under full-surface sprinkler or micro- sprinkler irrigation in this region.This is especially important in the first ten weeks after sowing.When water supply is limited, as it was in three winters during the trials, cover-crop performance is negatively affected. Cultivar and management Cover-crop trials were conducted over ten years in a vineyard of Sauvignon blanc grafted on Ramsey. The vines were trained on a seven-strand double lengthened Perold trellis system. Grapevines were spaced 1.5 metres apart in rows spaced 3 metres apart. Where else do these results apply? The site near Lutzville represents the semi-arid winter rainfall regions, as well as sandy soils in other regions where grapevines are cultivated, such as the Hex River valley. Cover-crop selection .............................................................................. p68 Cover-crop establishment . .................................................................... p83 Fertilisation of cover crops .................................................................... p85 Effect of cover crops on water use ..................................................... p122 Effect of cover crops on soil carbon and minerals ........................... p135 Effect of cover crops on grapevine nutrition and performance ....... p159 Where to find details of trials in this region

43