ROOT PRUNING AND TRUNK SCORING HAVE LIMITED EFFECT ON YOUNG BEARING APPLE-TREES

To control excessive growth, vigorous 'Smoothee Golden Delicious', 'Jo nagold', 'Empire', and 'Gala' apple (Malus domestica Borkh.) cultivars on Malling 7A (M.7A) rootstock planted at close in-row spacing (2.5 o r 1.8 m) were mechanically root-pruned (RP), trunk-scored (TS; ringing ), or both, annually for 3 to 5 years beginning in the fourth leaf. Tr ees were grown in a deep, well-drained, fertile soil and supplied with trickle irrigation. RP reduced terminal shoot length in 2 of 5 years on 'Smoothee Golden Delicious'; trunk cross-sectional area (TCSA) was not affected by RP. TS reduced terminal length in 3 years and TCSA in each of 5 years of treatment on 'Smoothee Golden Delicious'. Bloom den sity was not affected by RP on 'Smoothee Golden Delicious' but was inc reased by TS in two of the three years measured. RP reduced terminal s hoot length in 'Gala', 'Empire', and 'Jonagold' in most years and TCSA in 1993 for all cultivars. TS had no effect on shoot length or TCSA i n these three cultivars. Effects of RP and TS on yield and fruit size varied with year and cultivar. In general, the effects of RP and TS we re inconsistent and often failed to reduce shoot growth or canopy spre ad. No practical advantage was recognized from these techniques for yo ung apple trees growing on a fertile site with trickle irrigation.