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  • Author or Editor: Jeffrey W. Burcaw x
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The authors have developed a mathematical model designed for shade-intolerant tree crops which describes the amount of intertree shading in an orchard. These data are used to formulate an optimal orchard design based on shading reduction in orchards for any tree crop during any developmental window at any global location for either continuous canopy hedgerows or non-intersecting canopies for several different orchard geometries. Variables include tree shape, orchard geometry intertree spacing, row orientation, time and day of year, and geographical coordinates. Optimal orchard designs are based upon the total amount of unshaded canopy surface per unit area which each orchard configuration confers. Results indicate extensive variability of intertree shading between hedgerow and non-intersecting canopies to be largely a function of latitude, regardless of other variables.

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The authors have developed a computer model designed for shade-intolerant tree crops which describes the amount of intertree shading in an orchard. These data are used to formulate an optimal orchard design based on shading reduction in orchards for any tree crop during any developmental window at any global location.

Tree shape is modelled as an ellipsoid bisected about the semi-minor axis, with ellipsoid dimensions and eccentricity altered to reflect growth stages of the trees. Intertree shading is measured as the surface area of the projected shadow on the ellipsoid. Variables include crop, light extinction, ellipsoid dimensions, intertree spacing, orchard geometry, time and day of the year, and geographical coordinates. Simulations compared the sunlight-related attributes of a variety of orchard geometries for different growth phases of the trees during different parts of the year for several global locations. Results indicate extensive variability of intertree shading to be a function of latitude, regardless of other variables.

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The relative intolerance of pecan trees to low light environments suggests a need for the development of sunlight management strategies that optimize orchard productivity. Current strategies exhibit little emphasis on integrating sunlight interception, tree growth, and orchard design within this context. Therefore, there is a myriad of geometrical variation among commercial orchards and an associated difference in productivity.

We have developed a mathematical model incorporating computer simulations of pecan tree growth in a wide variety of orchard situations. Variables include tree shape, intertree spacings, geometrical pattern within the orchard, geographical coordinates, and time and day of year. This model predicts the extent of shading during the daily interval of maximum photosynthesis for any combination of these variables. It can also be used by the orchardist to establish orchards in which trees receive maximum levels of sunlight within specific windows of time; for example, during the period of nut filling or during the accumulation of dormant season assimilate reserves.

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Tree crops are often planted at particular geometrical and spacing patterns with little or no quantitatively based data on how the arrangements influence sunlight interception and productivity.

We have developed a mathematical model describing intertree shading derived from computer simulations of tree growth and light extinction through the canopy. Variables include tree shape, intertree spacings, orchard geometry, geographical coordinates, season, and time of day. This model predicts the extent of intertree shading during the daily interval of maximum photosynthesis for any combination of these conditions and indicates that optimal orchard design is unique for each latitude and tree crop. It can be used by the orchardist to establish orchards in which trees receive maximum levels of sunlight within specific windows of time; for example, during the period of fruit development or during the accumulation of dormant season assimilate reserves.

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