PRINCIPLES OF ORCHARD SYSTEMS MANAGEMENT OPTIMIZING SUPPLY, DEMAND AND PARTITIONING IN APPLE TREES
Research in the last 30 years has elucidated the importance of light interception and utilization to potential productivity. To take advantage of the potential, tree canopy management techniques have been developed that help improve the balance of partitioning of dry matter between the crop and the vegetative development. Productivity of healthy orchards is primarily limited by total light interception, but actual productivity appears to be limited by light interception by leaves supporting the fruit (mostly spur and bourse leaves) around 3–4 weeks after bloom. Viewing the apple as a wild plant suggests that vegetative growth to acquire limiting resources early in the season is highest priority and that fruit drop is extremely variable since it can be caused by any resource limitation. Insufficient light is an important resource limitation in different climates and within canopies. Early season shade reduces fruit set since it reduces fruit growth more than competing shoot growth. Later-season exposure is important to obtain good flowering and maintain leaf photosynthetic ability and spur vigor. Summer pruning or late season mite damage can reduce whole canopy gas exchange and final fruit sizing. Experimental data and computer modeling indicate that carbon deficits are most likely at about fruit set time and in the last weeks before harvest. Future research will probably emphasize reduction of tree-to-tree variability in productivity via more precise management of individual trees as is done now with pruning and training. Modern technologies like global positioning, geographic information systems and computerized equipment controllers are providing opportunities to extend precision management to more cultural practices like thinning and pest management.
Lakso, A.N. and Robinson, T.L. (1997). PRINCIPLES OF ORCHARD SYSTEMS MANAGEMENT OPTIMIZING SUPPLY, DEMAND AND PARTITIONING IN APPLE TREES. Acta Hortic. 451, 405-416
photosynthesis, Malus domestica, temperature, light, carbon balance, pruning, training, respiration