SOIL PREPARATION

CHAPTER 4

FIGURE 4.6: Formation of callus tissue and new roots of 99Richter after root pruning (Van Zyl & van Huyssteen, 1987) (Photo: ARC Infruitec-Nietvoorbij).

Timing is an important consideration when root pruning is considered. In South Africa grapevines have two peaks of active root growth per season, namely immediately after budding in spring and again in the post-harvest period during autumn. It is recommended that root pruning takes place after harvest since root regeneration will be better during the active root growth period than in the rest of the season. Furthermore, post-harvest root pruning is preferred because for grapevines the seasonal cycle of aboveground growth is almost completed by then, giving them time to recover and allow compensatory root growth before the new season starts. Both water-logged conditions as well as dry soil after root pruning will negatively affect root regeneration. This conclusion is supported by experiments done in Australia which indicated that the effectiveness of ripping between rows depends on the rainfall conditions of the season (McCarthy et al ., 2010). Consequently, optimum irrigation and fertilisation programmes should be maintained after root pruning in order to enhance root regeneration and growth into the loosened soil. Grapevine response is also affected by the severity of root pruning. In a field experiment, the effect of an actively-growing cover crop combined with regular and severe root pruning of a 13-year-old Colombar vineyard on own roots was compared to clean cultivated as well as permanent cover crop treatments. The vineyard was planted on a deep calcareous Hutton soil at Lutzville in the Olifants River valley of South Africa (Saayman & Van Huyssteen, 1983). In this experiment, deep tillage was carried out using a two-tined ripper

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