SOIL PREPARATION

CHAPTER 4

instances ripping was conducted in autumn, i.e. in the post-harvest period. A once-off ripping of the entire inter-row area in vineyards showed that grapevine response is affected by the presence or absence of roots in the mid-row area during the loosening action (McCarthy et al ., 2010). Canopy size and yield of Shiraz decreased significantly (yield decreased by 60 % in the first year) during the first two years after ripping of the mid-row when a significant number of roots had already been present prior to the loosening action. It took three years for the grapevines to recover to their original performance. With no or only few roots present in the second experiment, ripping of the mid-row had little effect on grapevine performance initially, but yield was significantly better than that of the control in the third season. Unfortunately there are no results to indicate whether the grapevine performance in the above-mentioned two experiments continued to improve in the long run. In another experiment conducted for seven years in a Shiraz vineyard, treatments were applied in spring (McCarthy et al ., 2010). The effect of ripping between rows to loosen tractor wheel compaction was somewhat less beneficial than the application of mulch along the vine row. Yield response to ripping was positive and significantly so in some years, but vine growth only increased significantly in the 4th and 5th vintages on the lighter and heavier textured soil zones in the experiment. Even in the seventh vintage after treatment application, yield and canopy growth were still positive albeit not significant anymore. In general, ripping between the rows did not affect berry quality. These Australian studies again demonstrated the value of having roots exploiting the inter-row area in a vineyard, the time it takes for the root system to recover after severe root pruning, and also the limited longevity of ripping the inter-row area (McCarthy et al., 2010) . This research also showed that grapevine response to surface mulching is more predictable than its response to the loosening of the inter-row area, especially if this area did not contain roots initially. An interesting approach was followed in a recent South African study by Moffat (2017) who compared root pruning alone with combinations of root pruning and the incorporation of 57 t/ha of compost (dry material). Before treatments were applied, the vineyard grew poorly in patches and penetrometer readings indicated soil compaction. The compost was incorporated into the soil using either a furrow plough or a small excavator. The actions were conducted in alternative rows as well as on plots where every row was treated. Root pruning per se had no positive effect on vegetative growth and yield, but when compost was combined with the two tillage operations, yield and cane mass improved significantly during the two consecutive seasons immediately after the treatments were applied. No additional benefit was obtained by working in every row. Further research should indicate whether the grapevine response

SOIL PREPARATION | 57