Vine size is critical. If vine size is low, there will be little shading within the canopy and most training systems will be suitable. As vine size increases crop potential goes up, but so does shade potential. More care must be taken to ensure an efficient display of canopy, one that maximizes the amount of leaf area exposed to the sun and minimizes shading of the renewal area. Shaded renewal areas result in the pro duction of low quality canes.
The bulk of this presentation will be devoted to a description of training systems in use today, and a discussion of their attributes. This discussion will not describe several systems widely used 50 years ago. Typical of these is the Chautauqua system. They have been abandoned because they are suitable only for small vines, they have shaded renewal areas and they require high labor inputs such as summer tying.
Four (or Six) Arm Kniff in (4-AK) differ only in the number of arms and hence canes (Fig. la). They were once extensively used but are not much used now. They offer some advantages, primary of which is the fact that they are easy to visualize and to establish. They suffer from several disadvantages. They are not well adapted to mechanical harvest. When slapper type harvesters are used, they must be run so aggressively that considerable vine injury may result. With all but small vines, the lower arms are heavily shaded and thus the cane quality at these positions will be poor. In addition there is a problem with apical dominance. Apical dominance occurs when the shoots growing at the end of a cane (near the cut) suppress the growth or development of shoots growing from buds originating near the base. Obviously, as cane length increases apical dominance increases. There are two ways to combat this phenomenon, 1) use shorter bearing units (spurs) or 2) orient the canes so that the apex is below the base of the cane. This helps because gravity slows the movement of the inhibitory substances. So to sum we recommend the 4-AK system to if 1) your vine size is small or 2) if you are so unsophisticated that you are not able to visualize a more com plex training system. It seems to me that if that represents your vineyard's potential in the first case or your own poten tial in the second, you don't belong in the vineyard business.
Umbrella Kniff in training (UK) (Fig. 1D) overcomes some of the basic limitations of 4-AK. In effect the lower, shaded arms are eliminated and all canes originate from the upper arms. Also the canes are bent so that apical dominance is minimized. Thus the renewal area is relatively unshaded and the arms do not tend to become rapidly extended. UK is also more adapted to mechanical harvest.What are it's disadvantages? Although the shade problem will not be as great as with 4-AK, large vine size still results in excessive shade and a reduction in cane quality. It is not well adapted to varieties with short internodes (the space on a cane between the buds). Our native varieties tend to have long internodes and canes can be brought over the top wire, bent and tied to the bottom wire at a point nearly midway be tween the vines without exceeding 12-14 nodes. The French- American and vinifera varieties have short internodes. A cane long enough to reach to the bottom wire will have too many nodes and overcrops will follow.
While mechanical harvesting is feasible with this system, there is no mechanized pruning system presently envisioned which will work on UK trained vines.
Hudson River Umbrella (HRU) (Fig. lC) training extends the arms o an UK traine vine into cordons from which short arms or canes originate. If offers many advantages. 1) Apical domin ance is combated. 2) The renewal area is not shaded, especially if shoot positioning is done. 3) Shoot crowding and hence within canopy shading can be minimized because of the opportuni- ty to distribute the retained nodes both horizontally and ver tically. Because of this, HRU is equally adapted to varieties with long or short internodes. 4) The large trunk-cordon sys tem provides a large resevoir for carbohydrate reserves. Re serves which are utilized during growth in the spring. 5) The need for tying is minimized depending on the variety. 6) With 1800 pruning (removing all growth from the top one-half of the cordon), shoot positioning and short vertical arms, HRU trained Concord vines may be mechanically pruned.
There are, of course, disadvantages as well. These primarily are expressed with varieties other than our native American ones. The large amount of trunk and cordon means not only that carbohydrate storage is maximized, but that sites for winter injury are also maximized. The top wire cordon ensures little shading of the renewal area, but it eliminates any sup port for upright growing shoots which are thus more subject to wind breakage. The final and perhaps most important dis advantage is that the large trunk-cordon system has many sites for base buds. Thus the non-count crop that arises from base buds and is not controlled by balance pruning is maximized. This results in the need to manually adjust crop or to suffer the consequences of automatic overcropping on most French- American varieties. Conversely these buds can be of benefit because they can serve as a reserve crop when the count crop is lost due to spring freeze.
If the vine size is so great that the growth on properly managed HRU trained vines still results in an excessively shaded renewal area, then conversion to Geneva Double Curtain (GDC) (Fig. lE) training should be considered. In es sence, GDC is an extension of HRU that further reduced shade by dividing the canopy into to discrete curtains of foliage. To maintain these curtains, the vines must be shoot positioned. HRU and GDC share similar advantages and disadvantages. The difference is that GDC is more expensive to establish and to maintain, but it will result in increased production/acre and reduced cost/ton in situations where HRU results in too much internal canopy shade. For Concords this appears to be in the neighborhood of 2 1/2 lbs. of prunings per vine when the within the row spacing is 8 feet. GDC is well adapted to mechanization of both harvest and pruning.
The training systems discussed above were presented in what seems to me to be a logical sequence when considering train ing options for our native American varieties. As discussed above the addition of other varieties both French-American and vinifera to our culture has complicated our decision-mak ing. This is because they differ in that they have upright growth habits and smaller, thinner leaves all of which reduces the amount of intra-canopy shading. They also have more fruit per retained node and a more productive base bud system. This means that the grower is not necessarily striving to increase the fruitfulness of his canes, but may instead be interested in combating other problems such as winter trunk injury. One system that has proved adaptable to many of the French-Ameri can varieties is Modified Keuka High Renewal (MKHR) training (Fig. lB). It is useful in that it 1 gives support to young shoots and so reduces shoot breakage on these upright growing varieties. 2) It has a minimal trunk system so base buds and non-count crop are minimized as is the amount of trunk tissue exposed to low winter temperature. However, at the present time we know of no way that MKHR trained vines may be properly mechanically pruned.
This completes the discussion of the predominant training sys terms use in New York. There are two others which are some times used and deserve mention. Mid-wire Cordon training can be thought of as HRU on a mid-wire. It offers the flexibility of distribution of canes and/or spurs of HRU but puts the head low to give shoot support. This is the most commonly used system in California, and is the system that mechanical prun ing work is centered on outside of New York. It appears that it may be suitable for varieties which have a high crop per retained node and which have very winter hardy trunks. The tnedency for fruitful base buds is proably of benefit with this sytem to combat the tendency for arms to become too long.