# Tree Planting Density and Canopy Position Affect 'Cerasuola' and 'Koroneiki' Olive Oil Quality
## 3 Results and Discussion  
### Production and Fruit Quality  
The influence of cultivar, planting density, and canopy position on production and fruit characteristics is presented in Table 1. Fruit yield ranged between 4.9 and 9.2 kg/tree. MD trees of both cultivars showed higher fruit yield than HD trees. The same trend was observed for yield efficiency with MD giving the highest values (0.2 kg cm\({}^{-2}\)). The highest yield per hectare was obtained with 'Cerasuola' at HD. These results are in agreement with a long-term study on 'Arbequina', where fruit and oil production per tree responded markedly to row spacing after six years from planting with higher values at a greater planting distance [32]. In 'Cerasuola', fruit yield expressed in t ha\({}^{-1}\) indicated that lower fruit yield per tree of HD was compensated by the larger number of trees per hectare. In contrast, 'Koroneiki' did not show significant differences between HD and MD, suggesting that yield potential of a single 'Koroneiki' tree was reached at lower densities. Results on the percentage of fruit yield harvested in the upper or lower layers of the canopy demonstrated that the majority of the production occurred in the upper layers. 'Cerasuola' presented the biggest differences in fruit distribution across the canopy. Percentage of fruit production in the lower layers of the canopy was higher than previously described by [PERSON] et al. [33] for 'Arbequina' in the south of Spain (17%), indicating that cultivars (growth habit, canopy density, and vigor) and cultural practices (mainly pruning) have a great influence on fruit distribution within the canopy. 'Cerasuola' presented higher fruit weight than 'Koroneiki' (Table 2). Fruit weight was not affected by planting density or canopy position, suggesting that any possible difference in fruit growth must have been canceled by the fruit's ability to attract assimilates from distant areas of the canopy during development [34]. During maturation, most of the chlorophyll is degraded and replaced by anthocyanins, producing a change in color from green to black in the olive fruit, commonly visually evaluated by the maturity index (MI). MI ranged between 2.2 and 3.3 and differences between upper and lower layers of the canopy were larger in HD than in MD (Table 2). This is likely due to a less homogeneous distribution of the light intercepted by the canopy when the trees are close to one another [35]. Percentage of black peel was assessed by image analysis. The same method applied in this study was previously used to study peel color and maturity level of oranges, apples, peaches, and nectarines at harvest [28; 36; 37]. In olive, percentages of black peel did not follow the same trend as MI values. In 'Cerasuola', MI of fruits from upper canopy layers of HD trees was significantly lower than fruits from MD trees, while their percentage of black peel was not significantly different. Differences between these methods can be explained by the color changes in the peel of the fruit from both cultivars and the methodology applied. In 'Cerasuola' fruits, the darkening of the peel starts on one side of the fruit and then spreads to the whole fruit, creating higher variability in the percentage of black peel. While in 'Koroneiki', the black peel starts from the tip of the fruit and uniformly expands around the fruit. To determine MI, fruits were separated into groups based on the amount of dark skin color, and in fruits where the color was more uniform, like 'Koroneiki', the MI relates better to the percentage of black peel. On the other hand, in 'Cerasuola', the MI methodology allows for determination of the intermediate color break between green and dark, detecting a greater difference between samples than the percentage of black peel. These results show how subjective the MI can be and how limiting the use of a nonsubjective method is at higher maturity stages.