12.5 Horticultural production

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Figure 12.26 Peach trees trained to a Tatura trellis. Mechanised summer pruning, as shown here, keeps vegetative vigour in check, improves canopy penetration of sunlight, and thus enhances flower bud differentiation for next year's crop. This well-maintained orchard at the Horticultural Research Station, Tatura (State Department of Agriculture, Victoria), returned high yields soon after establishment compared with conventional orchards based on widely spaced trees (see Colour Plate 62)

(Photograph courtesy P.E. Kriedemann)

Compared to annual crops or plantation forests, perennial horticultural fruit crops offer wide flexibility in the physical arrangement of their canopies in space. Not only can the size and shape of the canopy be dramatically altered by spacing, pruning and training, but the canopy can be physically constrained by a support structure of posts and wires into various forms, for example the V shape of the Tatura peach trellis (Figure 12.26; van den Ende et al. 1987), the horizontal form of the Lincoln apple canopy (Dunn and Stolp 1987), the pergola or T-bar training of kiwifruit or a variety of divided canopy forms of grapevines (Figure 12.27; Smart and Robinson 1991).

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Figure 12.27 Concord grapes (Vitis lubruscana) trained as either a single canopy (a) or divided canopy (b) growing as north-south rows under natural rainfall at Hector in upper New York State (near Cornell University Geneva Experiment Station). Naturally pendulant shoots of Concord grapes produce a dense canopy with reduced fruitfulness when vines are trained on a single wire. Light climate and flower bud differentiation is greatly improved when a canopy is managed as a double curtain of positioned shoots, and known colloquially as a 'Geneva Double Curtain'. Grape productivity per length of row can be more than doubled (Shaulis et al. 1966a, b). Yields from irrigated Vitis vinifera trained as a divited canopy (c) can be similarly improved (May and Shaulis 1971) (see colour plate 63)

((a) and (b) Photographs courtesy P.E. Kriedemann; (c) photograph courtesy E.A. Lawton)

In many of these cases, large changes in canopy form have been developed due to the availability or the possibility of machine harvesting. Changes in canopy management have accompanied machine improvement, recognising that sustainable cropping calls for horticultural rather than engineering solutions. With some perennial fruit crops, for example apple and pear, dwarfing rootstocks provide an alternative means of constraining canopy volume.

 

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