Light relations in orchard systems

The optimization of light interception is essential for the production of highquality fruit. High light interception is required for high yields, whereas insufficient light exposure may lead to inferior flowering and a reduction of many characteristics of fruit quality. Orchard configuration is important for the manipulation of light utilization. In this context, the influence of planting density, arrangement, tree size and shape on light interception was quantified in a model approach. The results were evaluated with the use of datasets from experiments with apple.From the results of the calculation of light absorption and canopy photosynthesis, it could be inferred that early cultivars having a growing season of only four months achieve about the same potential production over a wide range of temperate regions. The production of cultivars with a longer season would, however, increase by at least one tonne fruit (fresh weight) per ha for every degree lower latitude. On the other hand, production at low latitudes may suffer from higher respiration costs.A model for the assessment of light transfer through trees was used to analyse the influence of density, planting system, and tree size and shape. It was concluded that trees with a conical shape have better light penetration into the lower tree parts than have those with parabolic or cylindrical shapes. Light interception and the amount of well-illuminated canopy increase with planting density particularly 9 leaf density of the crowns is not increased. Systems with a low ratio of between-to- within row distance (rectangularity) should intercept light very efficiently.In experiments, planting density was found to be the most important orchard factor for production per ha, which was actually due to leaf area. Systems at low rectangularities produced considerably more well-coloured fruit than did those at higher rectangularities. The product" of three-row bed systems on a triangular design lagged behind that of other systems. A tall bit open tree was found to produce more well-coloured fruit than lower trees with a higher leaf density did. It is concluded that for fruit growers light interception is a key factor for the optimization of orchard management, that can be manipulated by planting density, planting system, and tree size and shape.