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- Author or Editor: James Schupp x
- Journal of the American Society for Horticultural Science x
Abstract
Vigorous 15-year-old ‘Melrose’/M.26 apple (Malus domestica Borkh) trees were mechanically root-pruned annually for 4 years at full bloom on two sides of the trunk at a distance of 60 or 80 cm and to a depth of 25 or 50 cm at each distance. Compared to unpruned controls, trees that were root-pruned had reduced trunk cross-sectional area, shoot length, leaf size, pre-harvest fruit drop, fruit size, and pruning time. Although fruit yield was unaffected, yield efficiency, fruit color, and soluble solids were increased by root pruning. Canopy light penetration was increased, as was spur quality. Generally, pruning 60 cm from the trunk had a greater effect than pruning at 80 cm, while pruning depth had no influence.
The characteristics of 1-year-old vegetative spurs growing on 2-year-old branches were measured on 28 `Delicious' apple (Malus domestica Borkh.) strains growing on M.7 rootstocks at Clarksville, Mich., and on 23 strains of `Delicious' on M.7a rootstocks at Kearneysville, W.Va. Spur-type strains typically had densities >20 to 21 spurs/m, and high spur leaf numbers, leaf areas per spur, leaf areas per leaf, and terminal bud diameters, whereas values for standard strains were generally lower. However, for most spur quality characteristics, there was a continuous range of values between the extremes rather than any distinct grouping into either spur or standard type. At both sites, spur density was significantly and positively correlated with yield efficiency. In a related study, the spur characteristics of `Starkspur Supreme' were measured on nine rootstocks: M.7 EMLA, M.9 EMLA, M.26 EMLA, M.27 EMLA, M.9, MAC 9, MAC 24, OAR 1, and Ottawa 3. Spur leaf number and spur leaf area were both high with vigorous rootstocks, whereas spur density was low. The rootstocks MAC 9, M.9, and M.9 EMLA had the highest yield efficiencies.