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In tree fruit crops, the crop load is one factor that has an influence on the vegetative growth of the trees. However, since trees vary in leaf area and associated fruit bearing capacity, the number of fruit per tree alone is not sufficient to predict their vegetative growth. In the present study, it was investigated whether the leaf area to fruit ratio of trees variable in size and crop load, measured automatically with a LiDAR laser scanner, have an influence on growth properties of the annual shoots. Canopy leaf area, the number of fruit per tree and the leaf area to fruit ratio of apple trees from two commercial apple orchards of the cultivar 'Gala' grown on sandy soils were scanned with a LiDAR laser scanner over a two-year period (n=12 trees per orchard and year). Additionally, the amount of carbon partitioned to fruit and annual shoot growth was quantified for each tree in both years (n=36). No correlation between the number of fruit per tree and the canopy leaf area alone to the amount of carbon partitioned to annual shoot growth was found in both orchards. However, the carbon partitioned to fruit correlated to the leaf area to fruit ratio, while the amount of carbon partitioned to the annual shoot growth was only correlated to the leaf area to fruit ratio in the young orchard. The inter-tree variability in shoot properties has been described. Nevertheless, it was found that the leaf area to fruit ratio is a weak indicator for shoot properties in apple trees, especially in the mature orchards. [ABSTRACT FROM AUTHOR]

This paper describes an approach to estimate the photosynthetic capacity and derive the optimum fruit number for each individual tree, in order to achieve a defined fruit size, which is named as the fruit bearing capacity of the tree. The estimation of fruit bearing capacity was carried out considering the total leaf area per tree as measured with a 2-D LiDAR laser scanner, LALiDAR, and key carbon-related variables of the trees including leaf gas exchange, fruit growth and respiration, in two commercial apple orchards. The range between minLALiDAR and maxLALiDAR was found to be 2.4 m² on Pinova and 4.3 m² on RoHo 3615 at fully developed canopy. The daily C requirement of the growing fruit and the associated leaf area demand, necessary to meet the average daily fruit C requirements showed seasonal variation, with maximum values in the middle of the growing period. The estimated fruit bearing capacity ranged from 33-95 fruit tree-1 and 45-121 fruit tree-1 on the trees of Pinova and RoHo 3615, respectively. This finding demonstrates sub-optimal crop load at harvest time in both orchards, above or below the fruit bearing capacity for individual trees. In conclusion, the LiDAR measurements of the leaf area combined with a carbon balance model allows for the estimation of fruit bearing capacity for individual trees for precise crop load management. [ABSTRACT FROM AUTHOR]