Towards an Optimized Method of Olive Tree Crown Volume Measurement

Accurate crown characterization of large isolated olive trees is vital for adjusting spray doses in three-dimensional crop agriculture. Among the many methodologies available, laser sensors have proved to be the most reliable and accurate. However, their operation is time consuming and requires specialist knowledge and so a simpler crown characterization method is required. To this end, three methods were evaluated and compared with LiDAR measurements to determine their accuracy: Vertical Crown Projected Area method (VCPA), Ellipsoid Volume method (V E ) and Tree Silhouette Volume method (V TS ). Trials were performed in three different kinds of olive tree plantations: intensive, adapted one-trunked traditional and traditional. In total, 55 trees were characterized. Results show that all three methods are appropriate to estimate the crown volume, reaching high coefficients of determination: R 2 = 0.783, 0.843 and 0.824 for VCPA, V E and V TS , respectively. However, discrepancies arise when evaluating tree plantations separately, especially for traditional trees. Here, correlations between LiDAR volume and other parameters showed that the Mean Vector calculated for VCPA method showed the highest correlation for traditional trees, thus its use in traditional plantations is highly recommended.The authors thank the Ministry of Economy and Competitiveness of the Spanish government for financial support, and the pre-commercial procurement MECAOLIVAR project and the Interprofesional del Aceite de Oliva Español (IAOE) for its financial support. This research has been financed with FEDER funds. The first author also thanks the Spanish Ministry of Education, Culture and Sport for its financial support through the National Training Program of University Lecturers (FPU)