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Annual mechanical hedging in August or root pruning at bloom was used to control the growth of four apple (Malus domestica Borkh.) cultivars in two orchard systems planted at half the recommended in-row spacing. Trunk cross-sectional area (TCA) per hectare on the trellis system was 30% higher, a result that correlated (r = 0.80) to a 40% higher cumulative yield per hectare over 10 years compared to the central leader system. Over 10 years, the cumulative yield and TCA per hectare of `Smoothee Golden Delicious', `Empire', and `Redchief Delicious' were higher in the trellis than the central leader system, while these characteristics of `Lawspur Rome Beauty' were not influenced by orchard system. `Lawspur' had the highest TCA per hectare, cumulative yield per hectare, and greatest tendency toward biennial bearing of the four cultivars. Root pruning reduced all tree-size measurements, while hedging did not influence tree height or average shoot length. Yield and yield per TCA were reduced by hedging and root pruning, with the greatest reduction in yield caused by root pruning. Hedging increased cumulative yield per hectare with root-pruned trees intermediate between hedged standard-spaced trees. Trellis trees had a higher density of spurs and shoots and a higher leaf area index than trees on the central leader system. An evaluation of the treatment combinations using net present value analysis indicated that none of the treatments was a profitable investment. Of the top twelve treatments, as evaluated for 10 years, nine were the central leader and three the trellis system, with none of the trellis and only four of the central leader treatments being hedged or root-pruned. Results of this study indicate that orchard intensification is accomplished best by choosing appropriate planting distances and not by attempting to control growth mechanically on trees planted too close for optimum performance.

Abstract

Apple (Malus domestica Borkh.) cultivars Lawspur Rome Beauty (a terminal bearer), Smoothee Golden Delicious, and Redchief Delicious (a spur-type) on MM. 106 or MM.111 were planted as whips or feathered trees (branched during their initial year of growth in the nursery) with the feathers pruned or unpruned. During the first year of growth, feathered trees of ‘Lawspur’ made more new growth than trees planted as whips, and pruning the feathered trees further increased new growth. The branching status of trees at planting had no influence on the first year growth of ‘Redchief’ and ‘Smoothee’. Following the second growing season, feathered trees of ‘Lawspur’ and ‘Smoothee’ had increased trunk cross-sectional areas, but those of ‘Redchief’ were not significantly increased. In the third season, feathered trees of ‘Lawspur’ and ‘Smoothee’ produced higher yields than trees planted as whips. Feathered trees of ‘Smoothee’, left unpruned at planting, had higher yields than trees with the feathers pruned; however, the opposite was true with ‘Lawspur’. Average shoot growth of trees on MM. 106, planted as whips, was longer than on MM.111; however, the opposite was true with feathered trees. Total growth/tree on MM.111 was increased for feathered trees, but there was no effect of initial branching status on growth of trees on MM. 106. Calculation of present values indicated positive economic benefits resulting from planting feathered trees of both ‘Lawspur’ and ‘Smoothee’. There was no positive economic return generated by any of the treatments on ‘Redchief’ or ‘Smoothee’ planted as whips after 4 years of growth.