Vine development and vigour control

Efficient winegrape production, involving the adoption of mechanical harvesting and pruning to minimise labour inputs, has enhanced the competitive position of the Australian industry and underpinned recent developments in export markets. However, the long term viability and sustainability of the industry will also depend on the efficient use of natural resources, i.e. land and water, and the reduction of chemical inputs. Several recent studies indicate that there is considerable potential to manipulate, within a low input context, vine growth and development (i.e. both the canopy and crop) and to control vine vigour to facilitate both a sustainable and economically viable approach to quality winegrape production. Widespread adoption of mechanical pruning by hedging (May and Clingeleffer 1977) and minimal pruning systems (Clingeleffer 1983, 1992) followed the introduction of mechanical harvesters into Australia in the early 1970s. It is estimated that about 60% of Australian winegrape vineyards in both the warm irrigated districts and cooler regions are pruned mechanically leading to substantial savings in production costs. Although production in warmer regions is largely unaffected by hedging (May and Clingeleffer 1977), its use has led to vine vigour problems in the cooler regions because cuts through one-year-old wood induce strong growth (Clingeleffer 1983, 1992). This may result in large canopies with subsequent fruit shading and loss of quality, low shoot fruitfulness, poor productivity, and development of vines which are difficult to harvest mechanically. Vertical shoot positioning (using imported European equipment) is being adopted to some degree to reduce the negative effects associated with hedging. Trials with minimal pruning systems over 19 seasons have shown that the vine has the capacity, through balanced growth, to maintain its shape, productivity and fruit quality. Variants of minimal pruning have evolved in commercial vineyards in cooler regions with the adoption of crop control techniques for high-yielding vigorous vines. The purpose in using these techniques is to restrict yields to around 20 tonne/ha and ensure adequate maturity and fruit quality (Clingeleffer 1992). Techniques include the use of mechanical skirting after fruit set (Clingeleffer 1992, Kidd 1986) and mechanical crop thinning after fruit set (Clingeleffer 1992). With minimal pruning the number of nodes per bearer is controlled by abscission of immature non-lignified terminal growth. Virtually all mature lignified shoots from the previous season are retained. Their length varies from very short spurs to longer canes of 10–14 nodes, depending on variety and vine vigour. In cooler regions, both the high vine vigour and low fruitfulness of basal nodes have limited the adoption of mechanical hedging. Also, minimal pruning is not suited to hand picking, which is quite generally used in cool regions in the absence of many mechanical harvesters. Alternatively, hanging cane systems, based on Sylvoz (Hudson River Umbrella) with high cordons, are being used to reduce costs associated with trellising, annual pruning and shoot training of the traditional, vertically trained, cane pruned Guyot system (Clingeleffer 1992). Other methods suitable for full mechanisation of cane pruning have been based on principles derived from hanging canes and split cordon systems (Clingeleffer 1981). More recently a midpoint Sylvoz using a modification of the swing-arm trellis (Clingeleffer, 1981) has been used for commercial Sultana production and also has potential for winegrape production. The removal of side growth from minimally pruned vines has been adopted in some commercial vineyards and may be developed as a simple hanging cane system. This paper will report on available practices to manipulate vine development and vigour, with particular reference to the further improvement of low input management systems. Effects on canopy and crop development, wine style and quality will be discussed.