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In a field experiment the micro-climate and grape composition of four trellising systems viz., (a) Bush vines, ( b) Perold system, (c) Lengthened Perold, and (d) Slanting trellis were investigated and compared. Significantly more air movement, higher bunch and ambient air temperature as well as higher soil temperatures at 200 mm depth were recorded in the bush vines compared to the lengthened Perold and slanting trellis. Bunch temperature differences among trellising systems became most pronounced at 12h00 to 14h00.

To accommodate the excessive vegetative growth of a 9-year old, 3.0 m x 1.2 m spaced and vertically trellised Chenin bland99 Richter vineyard, vines were converted to double the original cordon length by removing alternate vines or by extending the cordon laterally in a horizontal plane as per Lyre trellising system. By extending the cordon, shoot vigour was reduced, resulting in an improvement in canopy appearance and microclimate, particularly in the case of the latter system (higher canopy:root volume ratio). Yield increased by 11 % and 65% for the vertically trellised vines with extended cordon length and those on the Lyre system, respectively. Grape composition was not affected, whereas the severity of Botrytis infection tended to decrease. Wine typicity was enhanced by trellis conversion. Labour input in terms of pruning, harvesting and seasonal canopy management was lower for the vertically trellised vines with extended cordon length, but higher for the vines on the Lyre system; the additional yield, however, still resulted in respectively 15 % and 69 % higher total income. The results showed that the "original" vigour (growth capacity) was better accommodated and distributed by extending cordon length, particularly for the Lyre system, thereby resulting in higher yields of at least similar grape and wine quality and higher income than before conversion.

This paper reviews the subject of canopy management with an attempt to develop principles. These principles provide guidelines for canopy surface area amount; spacing between canopies; within canopy shade, especially for the fruiting/ renewal zone; balance between fruit and shoot growth; and uniformity of location of fruit/renewal zones, shoot tips and cane bases. Field techniques of point quadrat analysis and canopy scoring are introduced as an aid to defining problem canopies. These techniques are cheap, quick and effective. A set of twenty-one numeric indices and descriptors to assess winegrape canopies is then presented as a winegrape canopy ideotype, which can be further used as management guidelines. Recent publications are reviewed from various aspects of canopy management. These include vigour control, shoot trimming, leaf removal in the fruit zone and training system responses. The paper concludes with presentation of the authors' unpublished data on the effects of canopy microclimate on yield and wine quality. The trial was conducted with the cultivar Cabernet franc on a deep, fertile soil in a cool, high rainfall region. Canopy division using the Ruakura Twin Two Tier doubled yield compared to dense, vertical shoot positioned canopies which are common in New Zealand. Shade caused reduction in all yield components, and also delayed fruit ripening and reduced wine quality. Similar results were obtained by comparing fruit production at different heights with the Te Kauwhata Three Tier trellis system, where lower tiers were shaded at the canopy exterior. The results confirm that grape yield and wine quaiity can be simultaneously increased by improved canopy management of shaded vineyards.

The swing-arm trellis, designed to improve mechanical harvesting of Sultana grapevines used for raisin or wine production and to allow partial mechanization of pruning, is described. The trellis consists of seven wires, i.e. a cordon-wire and three wires each Sf>aced evenly in the horizontal and vertical plane and supported by triangular frames attached to the trellis posts. The vines are pruned to cordons that produce shoots that grow upward and attach to the vertical wires. For use as replacement canes, these shoots are placed horizontally by rotation of the frames. The yield of Sultana vines trained in this way was equal to or better than that of control vines trained in the standard manner with canes twisted around a single wire. Over fo'!r seasons, total yield was 1,31 times more for fresh fruit and 1,25 more for sugar. The yield differences occurred mainly in two seasons and were due to the combined effects of more nodes, better bud burst, more fruitful nodes and, consequently, more bunches. The advantages of managing vines trained on the swing-arm trellis are discussed.

A field trial involving four trellising systems viz.( a) Bush vines, (b) Perold, ( c) Lengthened Perold, (d) 1,7 m Slanting trellis, showed differences of the utmost importance with regard to rooting densities, consumptive water use and the incidence of Botrytis rot. Soil physical conditions were dominant in determining root distribution patterns. The slanting trellis had significantly more roots than the other systems. The consumptive water use, however, was not affected by amount of roots but mainly by the micro-climate. Contrary to expectation, the largest trellising system did not show the highest consumptive water use, but under the experimental conditions the bush vines had the fastest evapotranspiration rate. Average crop factors of 0,313; 0,260; 0,241 and 0,205 were found from bud burst to harvesting for bush vines, slanting trellis, lengthened Perold and Perold systems respectively. The high evapotranspiration rate of the bush vines is attributed to higher ambient air temperatures, more air movement as well as less shading of the soil surface than in the case of the slanting trellis. Crop factors varied according to soil moisture content, indicating the need to determine these parameters for specific irrigation frequencies. The low crop factors determined in this experiment emphasize the high water use efficiency of vineyards and stress the need to adopt existing crop factors to recent findings. Significant differences which cannot be attributed to micro-climate conditions occurred among trellising systems. Grape juice analyses, carried out throughout the growing season, indicated a relationship between total nitrogen and arginine status and Botrytis cinerea determined immediately prior to harvesting. More Botrytis rot was found at lower cropping levels. More investigations as to the relationship among the incidence of Botrytis rot, cropping level and nitrogen status of the plant are needed.

Nine-year-old, intensively irrigated, 3.0 x 1.2 m spaced and vertically trellised (5-strand) Chenin blanc/99 Richter vines were converted to double the original cordon length by either removing alternate vines or by implementing a Lyre trellising system. In the former case the root volume was doubled, whereas in the latter case it was kept the same as for the non-converted vines. After five years, a root profile study showed that roots of the single-cordoned, vertically trellised vines with extended cordon were distributed beyond the original soil volume (before conversion); this was not the case for the Lyre system. No difference in root density occurred between vines of converted systems. The available soil volume was apparently better colonised by roots of the converted systems, mainly because of an increase in fine roots. The greatest reduction in individual shoot growth was found for vines trained to the Lyre system. Yield per vine varied according to cane mass. Yield per hectare of vines trained to the vertical trellis with extended cordon space and the Lyre system increased significantly. Yield:cane mass ratios of 11, 15 and 16 were found in the case of the vertical, the vertical with extended cordons and the Lyre systems, respectively. The results indicated that shoot growth was better accommodated and distributed by extending cordon length, particularly when the ratio of cordon length to root volume was increased (as for the Lyre system). Compensatory growth occurred when both above-ground and subterranean growth volumes were increased. Preventing compensatory growth by the root system, resulted in balanced growth and improved microclimatic conditions for pest and disease control and grape ripening. This principle may be implemented as a long-term solution to problems associated with excessive vigour.

The Shaw swing-arm trellis has increased mechanisation in dried grape production as it enables trellis drying of the grapes in the vineyard. However, cordon bunches that do not dry reduce the quality of dried fruit at harvest. Traditionally, foliar application of ammonium nitrate was used to remove cordon bunches, but results were inconsistent. In recent years, health and safety concerns have heavily restricted the use of ammonium nitrate in the agricultural sector. Use of alternate chemical treatments was investigated to find an alternative to ammonium nitrate for removal of cordon bunches in Carina Currant, Sultana and Sunmuscat dried grape production. Different doses of calcium nitrate and Ethrel® (21.7%, w/v, ethephon) were applied to grapevines at various stages of vine growth. Calcium nitrate applied at a rate of 2.6% (w/v) to the vine pre-bloom at the 6 to 8 leaf stage (LS) and 250 ppm Ethrel® applied at full bloom (10 to 12 LS) achieved the most effective results. Both treatments provide a cost effective alternative to ammonium nitrate without any significant negative impact on growth, fruit bearing of vines and yield in the following year. Separate application scheduling of calcium nitrate (at pre-bloom) and Ethrel® (at full-bloom) offers flexibility in spray (application) schedules a management practices.