Spatial Heterogeneity of Radiation Incidence and Interception for Kiwifruit Vines, and Implications for Fruit Quality

Abstract

The spatial heterogeneity of radiation incidence and interception for kiwifruit vine canopies was investigated in relation to trellis design, canopy shape, leaf area distribution and incident radiation at different depths within the canopy. Incident radiation was uniform across the surface of a canopy trained on a horizontal pergola trellis, but was frequently reduced in distal regions of the canopy surface for a vine trained on a T-bar trellis with faces inclined downwards, due to partial or complete shading. Leaf area index also tended to decline with distance from the central cordon, further reducing radiation interception in these zones. Incident radiation at any position within the canopy varied diurnally according to the leaf area between the sensor and the radiation source (which in turn was affected by the shape of the canopy trellis and by canopy growth during the season) and the fraction of total radiation that was diffuse. The relationship between spatial heterogeneity of radiation incidence and interception and heterogeneity of fruit growth and quality is discussed