Development of a dynamic model to estimate canopy par interception

Models of the shadows cast by orchard trees can provide useful information to assist in canopy and nutrient management, estimation of potential yield and water use. In this study, an analytical model was developed that calculates the shape, size, position and orientation of the shadows cast by the tree canopy and described the diurnal and seasonal changes in those shadows. The objective of this study was to derive analytical expressions to describe the positions and potential effects of shadows in time and space based on shape and size of the canopy, row and tree spacing, row orientation, and the latitude and the longitude of the orchard to compute canopy PAR interception considering the shading from neighbouring trees. The model was based on the assumption that canopies have spherical or ellipsoidal shape. Simulations were performed at different times of the day to study the shading patterns of trees and evaluated in terms of solar radiation received, transmitted and intercepted. The model was calibrated using field data to assist orchard design and canopy management based on lightbar scans obtained at different times of the day. The calibration procedure was tested on an almond orchard by comparing the shadows scanned and estimated by the model. The maximum average values between precision and recall were 87.50% and 87.75%, respectively.