INFLUENCE OF MECHANICAL ROOT PRUNING AND HEDGING ON PERFORMANCE OF APPLE TREES IN THREE MANAGEMENT SYSTEMS

Trees of ‘Golden Delicious’ apple were evaluated over 10 years in the following orchard systems: trellis, 1143 t•ha^-1 (TREL); interstem, 889 t•ha^-1 (INT); and central leader, 370 t•ha^-1 (C.LD.). Within each system trees were also planted at half the in-row spacing and annually either mechanically hedged (Hedg) in August or root pruned (Rt.Pr.) at full bloom. INT had the largest trunk cross-sectional area (TCA)/ha followed by the TREL system, while the C.LD. had smallest TCA/ha. Cumulative yield per tree followed tree size with C.LD. trees with the highest yield and TREL trees the smallest with INT intermediate. Cumulative yield per hectare and production efficiency (kg•cm^-2) were higher with the TREL and INT compared to the L.CD. The significant interaction for yield per hectare between orchard system and treatment was due to the increase in yield of both Hedg and Rt.Pr. treatments in the INT system with no benefit of these treatments with the other systems. The significant interaction of orchard system and treatment on cumulative efficiency was due to the reduction in efficiency of the TREL trees caused by planting at half-spacing and either hedging or root pruning. Spur density, leaf area index (LAI) and percentage of the leaf area due to spurs were highest in the TREL system. Hedging increased shoot density and LAI. Specific leaf weight (SLW) of spur and shoot leaves decreased from the top to the bottom of the canopy, while the percentage of spur leaf area increased. The midsection from top to bottom and central section from east to west had the greatest density of both spurs and shoots.