Figure 16.—Fine clusters on trained plants.
Pro and Con
The advantages claimed for pruning and training are:
Earliness.
High yield per acre.
Ease of cultivating and spraying.
Ease of picking.
No injury from snails and wire worms.
Quality of fruit:—size, color, smoothness and cleanliness.
Crop finished earlier.
Less sunscald.
The disadvantages claimed are:
Many plants required.
Reduced yield.
More blossom-end rot.
Higher cost of labor.
Cost and care of stakes and wire.
The validity of each of these points varies greatly with conditions; in fact, the answer to the whole question depends largely upon the location and the ideas of the grower. In trying to reach a conclusion, it is well to realize that training makes certain radical changes in the plant. It loses leaves through pruning, it is supported from the ground, and it is spaced differently. Since the leaves manufacture the basic substance for themselves, and for the rest of the plant, removal of leaves reduces the resources of the plant. H. C. Thompson[17] has found that the root system is reduced about in proportion to leaf reduction. It is fairly clear that single-stem training greatly reduces the yield per plant, and other methods result similarly in proportion to the severity of pruning. When plants are spaced closely enough together the yield may be brought up to that of areas unpruned and unstaked. Idaho experiments indicate that staking alone does not affect the total yield, but that it does favor early maturity under the different pruning systems. The disadvantages of training are largely economic. Will the marketing conditions justify the extra cost of staking and pruning?
Experiments have shown pretty clearly that sunscald, blossom-end rot and cracking are worse on trained plants. Using varieties of good foliage will help the first trouble while uniform and adequate water supply achieved by selection of suitable land, by building humus content of the soil and by irrigation will solve the latter two problems. Thompson found increased yield of early fruit. Other evidence is somewhat conflicting but, in general, it supports Thompson. It is generally agreed that pruned plants yield larger, cleaner and more perfectly formed and colored fruits. Ease of spraying or dusting and of picking is important.