ISHS Acta Horticulturae 707: VII International Symposium on Modelling in Fruit Research and Orchard Management
EVALUATING THE ACCOUNTABILITY OF TRUNK SIZE AND CANOPY VOLUME MODELS FOR DETERMINING APPLE TREE PRODUCTION POTENTIAL ACROSS DIVERSE MANAGEMENT REGIMES |
| Authors: | H. Wright, D. Nichols, C. Embree |
| Keywords: | canopy volume, TCA, ‘Honeycrisp’, orchard productivity |
| Abstract:
Trunk cross-sectional area (TCA) is the most common surrogate measurement for determining tree size and, indirectly, the capacity of that tree to produce fruit. When used in a ‘Honeycrisp’ cultivar crop density and apple (Malus domestica) fruit quality experiment there was a lack of consistency across sites in fruit size and yield for similar crop densities, based on TCA (fruit/cm²). This reduced confidence in the goal of defining the optimum density and made industry wide recommendations difficult. The ‘Honeycrisp’ experiment consisted of three commercial sites which had plantings of identical age, rootstock and nursery source, but differed in tree spacing, training, pruning and management. To better account for the inconsistencies between sites, methods of calculating crop density per cubic volume of tree canopy were examined (fruit/m3). The ‘contour method’ for approximating canopy volume was developed and tested. The established, but underutilized, simple cone along with the elliptical cone method for approximating canopy volumes were also tested. The simple cone (V = (⅓)  r² h) and elliptical cone (V = (1/12) a b h) methods require three measurements of the tree’s canopy and assume the contour of the tree’s profile to be straight.
The ‘contour method’ (V = ((¼) a b h) / (m(x) + m(y) + 1)) requires five measurements of a tree’s canopy.
The canopy volume is calculated by first equating the tree’s unique contour and then by integrating along the contour lines of one of the axis.
Using the Log10 scale the crop density was plotted against average fruit size across all sites cumulatively for the four methods, TCA, simple cone, elliptical cone, and ‘contour method;’ the variation accounted for using simple linear regression was 58.9, 78.8, 80.1 and 83.9 percent respectively.
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