2045 Bainer Hall
Modeling Canopy Light Interception for Estimating Potential Yield in Almond and Walnuts Trees
Francisco Rojo, Ph.D. Candidate
A knowledge of spatial variability in potential yield is needed for site-specific nutrient management in crop production. Models of potential yield are usually based on photosynthetically active radiation (PAR) data, which is rarely available in commercial orchards. The objectives of this project were: (i) to develop a model for PAR intercepted by almond and walnut trees based on data obtained from respective tree(s), (ii) estimate potential crop yield in individual or a block of five trees, and (iii) to analyze if the area of the shadows and light interception at any time can be obtained from aerial images. This project used proximally sensed PAR interception data measured using a lightbar mounted on a mobile platform, aerial images obtained from an unmanned aerial vehicle and a crop growth model to estimate PAR interception and potential yield in almond and walnut trees. An analytical model was developed, where tree canopy was assumed to be spheroidal in shape. PAR intercepted by a tree was estimated taking into account the effect of row spacing, tree spacing within the row, latitude and longitude of the orchard, day of the year and row orientation. Our results showed that the total amount of PAR intercepted by the tree at any time during the day can be found analytically using estimated tree canopy radius and optical density obtained using just one lightbar scan as a reference. Good correlations were found between yield (for both actual and potential) and absolute midday PAR intercepted for both almond and walnut trees. Additionally, the shaded area of trees was found to be correlated with the area of the canopy extracted from the aerial image and the Zenith angle.
2045 Bainer Hall University of California Davis