Abstract
Orchard vigour, defined as the intensity of vegetative growth, is an important indicator for crop management in fruit tree cropping systems. It is often evaluated in commercial plots by experts on a non-formalised basis or measured with a single variable known as trunk cross-sectional area (TCSA). In this article, we proposed a set of 11 tree or plot morphological vegetative variables for apple orchards and applied it on 117 farm plots in south-eastern France. Relationships between variables were studied by component analysis (CA) and plots were classified into four clusters according to the first two factors of the CA. These modelled vigour marks were compared to expert vigour marks on 14 plots. Plot modelled vigour classification was re-estimated with only three morphological variables and compared to the original classification. These morphological variables were: TCSA, number of water sprouts on the trunk and length of annual shoot at the distal part of fruiting branches at the bottom of the tree. The first three factors of the CA correspond to vegetative growth intensity, opposition between annual and cumulative growth and vigour balance, respectively. Modelled and expert plot vigour classifications were generally in agreement, except in the case of heterogeneous plots. Re-estimated and original modelled classifications were also in agreement, except in the case of older and more vigorous orchards. Results showed that plot vigour modelling based on these three morphological variables may be relevant. TCSA thus did not appear to be sufficient. Results are discussed in relation to plant architecture features.