YIELD AND LIGHT EFFICIENCY FOR HIGH QUALITY FRUIT IN APPLE AND PEACH HIGH DENSITY PLANTING
Increasing planting density in fruit trees allows higher yields but, above certain thresholds, often it also brings about vegetative unbalances of the tree, resulting in overcropping and alternate bearing. The trees tend to age more rapidly, with a loss of fruit quality. In apple this threshold is around 3–4,000 trees ha-1, despite recent attempts with much higher densities (8–10,000 trees ha-1). These orchards are by definition rather extreme and require careful management: use of “preformed” trees, root restriction, hormones/summer pruning, accurate thinning, etc. Furthermore, though capable of high yields, they often display poor fruit quality. A general goal is to optimize tree performance, from photosynthetic efficiency to carbon partitioning to fruit. The training system greatly impacts these two aspects, via light interception and leaf demography. Net photosynthesis for the whole tree appears lower than could be expected based on single leaf measurement, while the tight relationships between photosynthesis and respiration indicate the importance of light management of the canopy. In addition, partitioning is adversely affected by shading, in apple more so than in peach. This may impact more heavily on cropping efficiency (up to 30% reduction in apple) than on quantity produced. With the basic concepts well defined, orchard design and canopy architecture may vary greatly, after identification and evaluation of the specific factors locally limiting orchard performance. For example, the highest densities recommended for the fertile Po Valley (2,500 trees ha-1) may well be considered normal in less vigorous environments, although upper thresholds can be much higher (4,000 trees ha-1) for alpine environments.
Sansavini, S. and Corelli-Grappadelli, L. (1997). YIELD AND LIGHT EFFICIENCY FOR HIGH QUALITY FRUIT IN APPLE AND PEACH HIGH DENSITY PLANTING. Acta Hortic. 451, 559-568
Training systems, cropping efficiency, high density planting, photosynthesis, carbon partitioning, Prunus persica, Malus domestica, peach, apple