VARYING DENSITY WITH CONSTANT RECTANGULARITY: EFFECTS ON APPLE TREE PERFORMANCE AND YIELD IN THREE TRAINING SYSTEMS
In 1992, an experiment designed to assess the effect of varying planting density at constant rectangularity on apple tree performance, yield and fruit quality was initiated. Five tree densities (from about 1125 to 3226 trees ha-1), three training systems (Y-trellis, short spindle, tall spindle) and two scion cultivars ('Summerland McIntosh' and 'Royal Gala' on M.9) were tested in a fully guarded split-split plot with four blocks. Light interception increased linearly with tree density, reaching about 45% for the highest density in 1995. Light interception did not differ significantly among systems. Leaf area indices in 1995 ranged from 0.4 at the lowest density to 1.0 at the highest. Total spur leaf area per tree declined at the highest density, and was higher on the Y-trellis than either spindle system. Yield per tree declined from about 15 to 10 kg as density increased, but yield per hectare increased. Training system did not affect yield during the first four years. Mean fruit size for 'Gala' was slightly smaller on the Y-trellis in 1995. The percentage of highly colored fruits decreased in 1995 at high densities for both cultivars.
Hampson, C.R., Kappel, F., Quamme, H.A. and Brownlee, R.T. (1997). VARYING DENSITY WITH CONSTANT RECTANGULARITY: EFFECTS ON APPLE TREE PERFORMANCE AND YIELD IN THREE TRAINING SYSTEMS. Acta Hortic. 451, 437-442