High-Resolution UAV Imagery for Field Olive (Olea europaea L.) Phenotyping

Giovanni Caruso,Francesco Paolo Marra,Giacomo Palai,Tiziano Caruso

doi:10.3390/horticulturae7080258

Giovanni Caruso, Francesco Paolo Marra + Show 2 more

Open Access

https://doi.org/10.3390/horticulturae7080258

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Journal: Horticulturae	Publication Date: Aug 21, 2021
Citations: 18	License type: CC BY 4.0

Affiliation: University of Pisa, University of Palermo

Abstract

Remote sensing techniques based on images acquired from unmanned aerial vehicles (UAVs) could represent an effective tool to speed up the data acquisition process in phenotyping trials and, consequently, to reduce the time and cost of the field work. In this study, we assessed the ability of a UAV equipped with RGB-NIR cameras in highlighting differences in geometrical and spectral canopy characteristics between eight olive cultivars planted at different planting distances in a hedgerow olive orchard. The relationships between measured and estimated canopy height, projected canopy area and canopy volume were linear regardless of the different cultivars and planting distances (RMSE of 0.12 m, 0.44 m2 and 0.68 m3, respectively). A good relationship (R2 = 0.95) was found between the pruning mass material weighted on the ground and its volume estimated by aerial images. NDVI measured in February 2019 was related to fruit yield per tree measured in November 2018, whereas no relationships were observed with the fruit yield measured in November 2019 due to abiotic and biotic stresses that occurred before harvest. These results confirm the reliability of UAV imagery and structure from motion techniques in estimating the olive geometrical canopy characteristics and suggest further potential applications of UAVs in early discrimination of yield efficiency between different cultivars and in estimating the pruning material volume.

Highlights

The geometrical canopy characteristics derived by RGB images showed significant differences between cultivars and between planting distances (Table 2, Table S2)
Previous studies ascertained the ability of unmanned aerial vehicles (UAVs) and image analysis in geometrical canopy characteristics estimation in orchards and vineyards [22,33,34,35,36,37]
Geometrical canopy characteristics, such as canopy height, projected canopy area and canopy volume, were satisfactorily estimated (MAPE of 3.26, 10.40 and 9.25%, respectively) following the methodology proposed by Caruso et al [33]

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Olive groves are widespread in the Mediterranean basin, where 97% of total olive trees are grown [1]. Taking into account the new olive-producing countries Argentina, Chile and California) outside the Mediterranean Basin, olive trees can be considered one of the most representative tree cultivations in the world [1]. The diffusion of olive growing outside traditional areas of cultivation is mainly due to an increase in olive oil consumption over the last 20 years and to the availability of new planting systems (e.g., high-density and super-high-density) and more efficient orchard management strategies (irrigation and mechanized harvesting and pruning)

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