SOIL PREPARATION

CHAPTER 1

and special configuration of the drainage system, mean that such work must be completed before planting. Ridging, terracing of steep slopes, plant holes and even root pruning are further aspects of soil preparation that require special attention. Once one understands the principles underlying these practices, decision making becomes easier, e.g. when and how often root pruning should be done or whether mechanisation of planting fulfils the requirement for rapid root growth into the surrounding soil. Since soil preparation is primarily aimed at creating soil conditions that will allow root growth to sustain the desired grapevine performance, knowledge about optimum conditions for root growth and the relationship between roots and aerial growth is essential. The technique of soil preparation is to a large extent determined by soil type and the nature of the root impediments present. This can only be determined through inspection in a soil pit, combined with soil sampling and analyses. In addition to soil profile inspection, instruments such as the penetrometer exist that can be used to detect soil compaction and are suitable for application on farms. Considering the costs involved and the long-term nature of investment associated with establishing of vineyards, it will be worthwhile to employ the help of a soil expert. In the end it will be important to decide which kind of implement will be best suited to rectify a specific soil condition. Soil preparation can improve a soil, but if poor subsoil is e.g. ploughed to the surface, the end will be worse than the beginning. The South African wine and table grape industries are fortunate to have access to an array of implements and a pool of experience that can recommend the best horse for every course. Compiling all available knowledge together in book form has the additional benefit of identifying knowledge gaps as well as shortcomings in existing soil preparation practices. One such knowledge gap exists around the incorporation of organic matter into the soil during soil preparation. The prediction of the rate of natural re-compaction of different soils after loosening is also still lacking. The list of unanswered questions can be extended with issues around the practicality and necessity of removing old roots when vineyards are replanted, as well as the economic viability of some practices. In most cases where knowledge gaps exist, research has been done, but the investigations did not yield conclusive answers. Consequently research has to be expanded, repeated or done using different methods. Research on soil preparation is long-term in nature and the progress that has been made, is a tribute to researchers who were willing to dwell on the subject for many years.

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