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ARC Infruitec-Nietvoorbij shares research results with raisin and wine grape producers of the Lower Orange River
Danie van Schalkwyk, Neels Volschenk, Jan Avenant & Andries Daniels, ARC Infruitec-Nietvoorbij, Stellenbosch
ARC Infruitec-Nietvoorbij is committed to serving wine and raisin producers in the Lower Orange River to ensure that they remain abreast of the latest research in this field which will enable them to produce the best quality product. In an attempt to introduce producers to research results in a more practical way, researchers from the Viticulture section of the institute presented a farmers’ day at the Upington Experiment Farm and at SADOR in December 2008. This event was attended by 45 persons from the ranks of commercial and emerging farmers, as well as technical persons from the industry locally. The farmers’ day was co-ordinated by Danie van Schalkwyk from ARC Infruitec-Nietvoorbij.
One of the research sites visited was that of Neels Volschenk, where alternative cultivation methods are researched for wine grapes intended for the production of juice and distilling wine. There is an ongoing demand for alternative/cheaper methods to cultivate wine grapes and in this study scions from various grapevine cultivars were planted in rows 100 cm apart. The use of a scion entails a considerable reduction in establishment cost. The vines were planted at different widths in the row, some only 30 cm apart. Hedge poles were used for trellis poles in a low trellis system with a cordon at 60 cm and two adjustable foliage wires. The objective of the project is to establish an alternative system which will make it affordable for emerging farmings to grow wine grapes profitably on a relatively small piece of land. The management of the system is fairly intensive and the narrow rows necessitated adjustments to normal cultivation methods. One of the cultivars used in the trial is Villard blanc. This cultivar is a self bearer and can be cultivated on its own roots under normal conditions. Villard blanc is resistant to downy mildew and oidium and the study showed it to be resistant to berry rot as well. This attribute results in significant cost savings in the disease control programme. Yields of up to almost 40 t/ha have been obtained in the trial. Villard blanc is currently being planted on a large scale in the Northern Cape. The trial also entails an investigation into the use of various high-growing cover crops to protect vines with low cordons against frost in spring (Photo 1). Mr Volschenk discussed the results that have been obtained so far (Photo 2).
Trellis systems constitute the biggest part of vineyard establishment costs. Jan Avenant is currently evaluating alternative trellis systems for raisin grapes on the Upington Experiment Farm. The objective of this trial is to make use of cheaper trellis systems which will reduce the production cost of raisin grapes. During the farmers’ day Mr Avenant explained to producers the results that he has obtained so far using these systems (Photo 3). These systems include the Shaw 1 and 2, and Shaw 3 which are being evaluated in comparison to the gable system. The Shaw systems were designed to improve the utilisation of sunlight. They are easy to manage and on average they currently produce the same yields as the gable system. They also facilitate pruning and harvesting. Producers showed keen interest in these three systems and participated in discussions about the applicability of the system.
The production of raisins in South Africa is currently mostly dependent on two raisin grape cultivars, namely Sultanina and Merbein Seedless. The problem with Sultanina is that yields differ vastly from one season to the next and the average yields in the Lower Orange River are fairly low. Although Merbein Seedless produces higher yields, it requires more care during the harvest and drying process. Merbein Seedless is an extremely vigorous grower. It has to be pruned differently to Sultanina and it is also more susceptible to growth arrest disease. Consequently raisin producers are keen to find alternative raisin grape cultivars which produce more consistent yields, have higher yields than Sultanina and produce the same or better quality raisins. The table and raisin grape section of the Breeding and Evaluation division of ARC LNR Infruitec-Nietvoorbij has been creating new hybrids for some time and is evaluating imported cultivars to address this demand. The evaluation programme is currently under the direction of Andries Daniels who explained the objective of his programme to producers at the farmers’ day (Photo 4). Producers had the opportunity to taste raisins made from the most promising new hybrids. Among these hybrids were some which produced exceptional quality raisins. They will be further evaluated on a semi-commercial basis on producer farms as well as the experiment farm. It is already clear that some hybrids have great potential and they may be released to the raisin industry in the foreseeable future after virus cleansing.
SAD also participated in the presentation of the farmers’ day and SADOR was paid a visit to look at the practical implementation of a roof trellis for raisin grapes. During the visit Leon Loubscher from SAD explained the advantages and disadvantages of a roof trellis to the producers (Photo 5). The construction cost of a roof trellis is extremely high and great care should be taken to use the correct strength material for the erection otherwise the entire system might crash if some of the cables or wires break. The roof trellis is the only trellis system that utilises sunlight optimally. The management of the system is more labour intensive, however. These aspects as well as the cost of the system make it less appealing to producers. Mr Loubscher also showed producers one of the new imported raisin grape cultivars that they are evaluating. The cultivar produces consistently higher yields than Sultanina and also makes excellent raisins.
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