SOIL PREPARATION

They suggested that at least 4 vines and 14 observation tubes would be necessary to obtain reliable spatial root distribution when using this method. A further innovation used successfully to study root growth recently demonstrated that technology will undoubtedly make it ever easier and cheaper to study roots in future. In a study on apples, Stofberg (2018) used an ordinary document scanner to successfully scan roots against the walls of perspex chambers in a young apple orchard (Figure 4.5). Before installation, a grid that showed the exact position of the roots was engraved on the perspex sides of the chamber. The scanner was inserted into the chamber and the sides scanned in sections while images were captured on a laptop.

FIGURE 4.5: Perpex chamber permanently installed in the soil (left) and quality of root images (right) scanned inside the chamber using an ordinary document scanner (Stofberg, 2018) (Photos: J.E. Hoffman, Stellenbosch University). Many questions still remain regarding the behaviour and management of grapevine roots. One such question is the necessity and the practicality of removing old roots when a vineyard is replanted. It is normally recommended that residual root fragments in vineyards be removed before planting of the new vineyard in order to get rid of pests and diseases such as nematodes and phytophthora (Van der Westhuizen, 1981; Emmet et al ., 1992; ARC Infruitec- Nietvoorbij, 2002; Coulouma et al ., 2006). This is currently not being done – in fact it is impossible during deep soil preparation – and investigations are needed to determine the value and method of incorporating such a practice as part of soil preparation.

52 | ROOT RESPONSE TO SOIL CONDITIONS