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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. The need to improve apple orchard productivity and profitability has resulted in the use of new orchard management systems (Jackson and Palmer, 1989). The most proven method of increasing orchard efficiency is to intensify planting in these systems using a precocious, size-controlling rootstock combined with an appropriate management system (Barritt, 1989; Ferree et al., 1989b; Robinson et al., 1991). Unfortunately, many of the most precocious and efficient dwarfing rootstocks are susceptible to fireblight and significant losses can occur (Ferree et al., 1983). Generally it is uneconomical to plant trees on more vigorous rootstocks at very close spacings without some additional means to control size due to increased pruning costs and the tendency of the trees to produce excessive vegetative growth at the expense of fruiting. Mechanically hedging dormant trees, or during the summer, has been tried with only limited success (Ferree, 1976, 1979). Root pruning is another mechanical means of controlling tree size. Root pruning reduces growth, pruning time, preharvest drop, and fruit size while increasing fruit firmness and soluble solids concentration and improving fruit color (Ferree, 1992; Schupp and Ferree, 1987, 1988; Schumacher, 1975). Most of these studies on root pruning have been conducted on mature trees, but this technique has not been compared directly to other orchard systems or techniques designed to improve orchard efficiency. The present study was established to determine if mechanical summer hedging or root pruning could contain the growth of trees planted at double their recommended density in two orchard systems. In addition, the influence of the systems and treatments for publication 23 Sept. 1992. Accepted for publication 14 Feb. 1993. nd research support provided by state and federal funds appropriated to Agricultural Research and Development Center, The Ohio State Univeral article no. 264-92. The cost of publishing this paper was defrayed in e payment of page charges. Under postal regulations, this paper therefore ereby marked advertisement solely to indicate this fact. SOC. HORT. SCI. 118(6):707-713. 1993. on orchard efficiency, canopy composition, and economic performance were evaluated. Materials and Methods In 1981, ‘Smoothee Golden Delicious’, ‘Lawspur Rome Beauty’, ‘Redchief Delicious’, and ‘Empire’ were established in a four-wire trellis hedgerow on M.9 rootstock or a free-standing central leader on M.7 rootstock. A three-tree plot of each combination was established in a series of three plots per row at the recommended spacing for that cultivar and rootstock (‘Smoothee’ and ‘Empire’—M.7, 4.5×6m; M.9, 2.5×3.5m; ‘Redchief and ‘Lawspur’— M.7, 3.5×5m, M.9, 2×3.5m) and two plots were established in each row at half the recommended in-row spacing, with all rows running north to south. Trees in the plots at half spacing were either root-pruned or mechanically hedged. We recognized that the effects of spacing and either hedging or root pruning are confounded in this study; thus, even though the treatments are referred to as either hedged or root-pruned, the effects could be due, partly or totally, to the closer spacing. Root pruning on two sides of the trees 50 cm from the trunk and 35 cm deep was begun in 1983 and repeated annually at bloom with a tractor-drawn subsoiler (Geisler and Ferree, 1984) cutting at the same location each year. Trees were hedged annually in early August on two sides with a two-bladed sickle-bar mower set at a 75angle. The mower was positioned to remove 15 cm of growth from the east and west sides of the canopy until the trees filled their allotted space and then they were cut at the same location each year. The treatments were arranged in a split-plot design of four replications, with training system as the whole plot, cultivar as the split plot and spacing-pruning as the split-split plot. Tree height, spread, and trunk circumference were recorded annually. The yield from each tree was graded annually with a weight-sizer (FMC, San Jose, Calif.), set independently for each cultivar to divide the fruit into the following size classes, with the

Apple Tree Performance with Mechanical Hedging or Root Pruning in Intensive Orchards