Sensor-based Canopy Mapping Using Photosynthetically Active Radiation Interception in Y-trellis Tree Fruit Orchards

Abstract

<abstract> <bold>Abstract.</bold> Canopy interception of incoming photosynthetically active radiation (PAR) is an important factor affecting tree fruit orchard productivity. In traditional multiple-leader training systems, a positive correlation exists between PAR interception and yield. In this study, a sensor-based canopy mapping method was developed for measuring of PAR interception in Y-trellised sweet cherry (Prunus avium L.) orchard. A mobile sensor system capable of measuring PAR data under a constant data spatial resolution was development and used in field PAR data collection in two significantly different canopy stages of dormant (March, 2013) and full canopy (June, 2012). A mathematical model of canopy projecting position correction was developed to correct deformation of canopy projection caused by the sun position (i.e. solar zenith and azimuth angles), on PAR reading recorded at different time. Digital images of ten tree canopies were taken on dormant season to evaluate the accuracy of canopy projection correction. Results showed that the developed sensor system could obtain a 1.0 cm constant spatial resolution within the entire speed range of the mobile platform along the traveling direction. The relative errors of inclinations of 20 distinct segments on digital images and mapping images were from 0.2% to 9.6%, presenting the good performance of the canopy mapping method.