Productivity and Vigor Dynamics in a Comparative Trial of Hedgerow Olive Cultivars

Abstract

The hedgerow growing system is prevalent in new olive orchards worldwide due to its fully mechanized harvesting. Several works have been published to compare cultivars planted in this system, focusing on productivity and oil composition. However, little research has been conducted on the long-term evaluation of cultivars’ growth habits when trained in hedgerow systems and on how it affects their interannual productivity. In this work, we report the canopy growth habit, productivity, and their correlation for the ‘Arbequina’, ‘Arbosana’, ‘Koroneiki’, ‘Lecciana’, ‘Oliana’, and ‘Sikitita’ cultivars grown in a hedgerow system in Extremadura, central-western Spain, for 9 years. ‘Koroneiki’, ‘Arbequina’, and ‘Lecciana’ were the cultivars with the highest canopy growth, both in young and adult trees, and the ones with the highest pruning needs from 5 to 10 years after planting. The yield behavior in each of the years evaluated was stable in all cultivars except ‘Lecciana’. This alternate bearing was associated with the distribution of total yearly produced biomass between fruits and vegetative growth. ‘Oliana’, ‘Arbosana’, and ‘Sikitita’ were the cultivars with the highest proportion of fruit of the total biomass, and ‘Lecciana’ showed the lowest. This study indicates that cultivars with higher fruit proportions of total biomass might have better suitability for long-term growing in hedgerow formation, fewer pruning needs, and more stable productivity across the years. In this sense, in the climatic conditions considered here, ‘Arbosana’, ‘Sikitita’, and ‘Oliana’ could be the most suitable cultivars for this growing system.

1. Introduction

Olive cultivation has experienced a strong intensification in the last centuries, which has led to the emergence of hedgerow orchards [1]. This growing system is characterized by a high density of plantation, where olives form continuous hedgerows that are harvested using straddle machines. This dramatically reduces the labor needed for harvesting with respect to traditional or even intensive growing systems [1].

The high density of hedgerow olive orchards implies that only low-vigor cultivars with dense canopies can be used [2,3]. Tree canopies should be low enough to allow the straddle machine to pass over for harvesting operations. However, most olive cultivars available today are centennial and were selected by growers for low-density traditional growing systems; therefore, they are highly vigorous and not adapted for hedgerow growing [4].

Several comparative cultivar trials to determine the best cultivars suitable for the hedgerow system in different climatic and growing conditions have been reported [5]. Most of those trials have been focused on productivity [6] and oil composition [7]. As a result, only ‘Arbequina’, its seedling ‘Arbosana’ (Angjelina Belaj, personal communication), and, to a lesser extent, ‘Koroneiki’, have been reported to be suitable for this high-density hedgerow system [4]. Moreover, several breeding programs have attempted to develop new olive cultivars specifically adapted to the hedgerow system, such as ‘Sikitita’ [8], ‘Oliana’, and ‘Lecciana’ [9].

However, little research has been conducted on the evaluation of cultivars’ growth habits and their suitability to be trained in hedgerows [2,3]. These growth habits will determine the cultivars’ pruning needs to keep the hedgerow in a dimension sufficient to allow the straddle harvester to pass over [10,11]. As harvesting is fully mechanized in hedgerow orchards, pruning is now the costliest operation in olive growing [1]. The influence of vigor and pruning needs on productivity and biennial bearing are also of paramount importance in determining the suitability of a cultivar for a hedgerow growing system [12]. Differences in the partition of biomass production between vegetative (pruning) and reproductive (yield) organs have been observed for ‘Arbequina’, ‘Frantoio’ [13], and ‘Leccino’ [14] potted plants. To test the suitability of olive cultivars for the hedgerow system, it would be necessary to consider this biomass partitioning in field cultivar trials over long periods.

Therefore, in this work, we compare the canopy growth habit, productivity, and their relationship for six olive cultivars grown in a hedgerow system for 9 years. The ideal partitioning between vegetative and reproductive biomass in an adult hedgerow and the most suitable cultivars for hedgerow growing are discussed based on the data obtained.

2. Materials and Methods

2.1. Trial Description and Management

A cultivar comparative trial was planted in Finca “La Orden” (CICYTEX), Badajoz, central-western Spain (38°51′ N, 6°40′ W and 200 m of altitude), which has a typical Mediterranean climate (Figure S1). Minimum winter temperatures were above 0 °C and maximum summer temperatures were 35–38 °C, while annual rainfall was very variable, between 274 and 489 mm. The cultivars ‘Arbequina’, ‘Arbosana’, ‘Koroneiki’, ‘Lecciana’, ‘Oliana’, and ‘Sikitita’ were evaluated. For this purpose, the comparative trial orchard was divided into four blocks. In each block, three consecutive rows of 6 plants (18 plants) of each cultivar were planted and were considered the elementary plots. The elementary plots of the 6 cultivars were randomly sorted by block (randomized complete-block design). The 6 cultivars were selected due to being suitable for the hedgerow growing system [1,9]. Trees were planted in 2012 at 1.35 m × 3.75 m spacing (1975 trees/ha). The plants of all the cultivars had the same size and condition at the time of planting. The orchard was managed with standard practices to maximize productivity. Pruning was performed yearly from January 2015 and consisted of mechanical topping at 2.5 m height and manual removal of basal shoots up to 0.5 m height. Lateral pruning was manually applied to facilitate the correct passage of machinery, keeping the hedgerow between 120 and 170 cm wide. Weeds were periodically controlled with herbicide along the tree row and with mechanical tillage in the inter-row area. Irrigation was applied to cover water requirements [15] (Figure S1B). Fertilization was applied for optimal nutrition considering yearly biomass production and foliar analysis. An average of 80, 40, and 100 fertilization units of nitrogen, phosphorus, and potassium, respectively, were applied annually.

2.2. Measurements

For each elementary plot, the four central trees of the central row were evaluated. Trunk diameter was measured annually from 2014 to 2022 at 50 cm height and used to estimate trunk cross-sectional area (TCSA). From 2014 to 2016, tree canopies were still isolated; therefore, canopy volume (considered an ellipsoid) was calculated using total tree height and two perpendicular canopy width measurements performed with a calibrated stick using Formula (1)

$$Canopy volume={\displaystyle \frac{4}{3}}\times \pi \times {\displaystyle \frac{H}{2}}\times {\displaystyle \frac{W1}{2}}\times {\displaystyle \frac{W2}{2}}$$

(1)

where H is the plant height and W1 and W2 are the two perpendicular widths.

From 2017 to 2022, trees were already forming a continuous hedgerow; then, canopy volume was measured, dividing the hedgerow into three parts. Those measurements were carried out each year just before and then after pruning, and pruning volume was calculated as the difference between these measurements using Formula (2):

$$\mathrm{P}\mathrm{r}\mathrm{u}\mathrm{n}\mathrm{i}\mathrm{n}\mathrm{g} \mathrm{v}\mathrm{o}\mathrm{l}\mathrm{u}\mathrm{m}\mathrm{e}:\mathrm{C}\mathrm{a}\mathrm{n}\mathrm{o}\mathrm{p}\mathrm{y} \mathrm{v}\mathrm{o}\mathrm{l}\mathrm{u}\mathrm{m}\mathrm{e} \mathrm{b}\mathrm{e}\mathrm{f}\mathrm{o}\mathrm{r}\mathrm{e} \mathrm{p}\mathrm{r}\mathrm{u}\mathrm{n}\mathrm{i}\mathrm{n}\mathrm{g}\left(\mathrm{y}\mathrm{e}\mathrm{a}\mathrm{r} \mathrm{n}\right)-\mathrm{C}\mathrm{a}\mathrm{n}\mathrm{o}\mathrm{p}\mathrm{y} \mathrm{v}\mathrm{o}\mathrm{l}\mathrm{u}\mathrm{m}\mathrm{e} \mathrm{a}\mathrm{f}\mathrm{t}\mathrm{e}\mathrm{r} \mathrm{p}\mathrm{r}\mathrm{u}\mathrm{n}\mathrm{i}\mathrm{n}\mathrm{i}\mathrm{g}(\mathrm{y}\mathrm{e}\mathrm{a}\mathrm{r} \mathrm{n})$$

(2)

Canopy growth volume was calculated as the difference in volume before pruning in a given year minus volume after pruning in the previous year following Formula (3):

$$\mathrm{C}\mathrm{a}\mathrm{n}\mathrm{o}\mathrm{p}\mathrm{y} \mathrm{g}\mathrm{r}\mathrm{o}\mathrm{w}\mathrm{t}\mathrm{h} \mathrm{v}\mathrm{o}\mathrm{l}\mathrm{u}\mathrm{m}\mathrm{e}=\mathrm{C}\mathrm{a}\mathrm{n}\mathrm{o}\mathrm{p}\mathrm{y} \mathrm{v}\mathrm{o}\mathrm{l}\mathrm{u}\mathrm{m}\mathrm{e} \mathrm{a}\mathrm{f}\mathrm{t}\mathrm{e}\mathrm{r} \mathrm{p}\mathrm{r}\mathrm{u}\mathrm{n}\mathrm{i}\mathrm{n}\mathrm{g}\left(\mathrm{y}\mathrm{e}\mathrm{a}\mathrm{r} \mathrm{n}\right)-\mathrm{C}\mathrm{a}\mathrm{n}\mathrm{o}\mathrm{p}\mathrm{y} \mathrm{v}\mathrm{o}\mathrm{l}\mathrm{u}\mathrm{m}\mathrm{e} \mathrm{b}\mathrm{e}\mathrm{f}\mathrm{o}\mathrm{r}\mathrm{e} \mathrm{p}\mathrm{r}\mathrm{u}\mathrm{n}\mathrm{i}\mathrm{n}\mathrm{g}(\mathrm{y}\mathrm{e}\mathrm{a}\mathrm{r} \mathrm{n}+1)$$

(3)

Canopy pruning was performed in January and weighed in the four representative trees. Pruning material was classified into three groups: topping, lateral young (one-year-old) branches, and lateral old (two or more years old) branches. For each group, leaves and shoots were separated, weighed, and then dried in an air force oven for 72 h at 105 °C and weighed again. Therefore, the fresh and dry weights of the leaves and shoots of each of the three groups were determined per cultivar and year.

The four selected trees of each elementary plot were hand-harvested in the second half of November each year and the crops were weighed. Then, a straddle machine was used to harvest all the trees of the trial. An olive sample of 1 kg was taken for each elementary plot and three subsamples of around 35 g were taken and weighted. Then, they were dried in an air force oven at 105 °C for 48 h and weighed again. Those data were used to calculate fruit fresh and dry weight and moisture.

2.3. Data Analysis

The alternate bearing index was calculated using Formula (4) as previously reported [16]:

$$BI={\displaystyle \frac{\sum _{2014}^{2022}\left(\right(\left|yi+1-yi\right|\left)\right)/(yi+yi+1))}{\mathrm{n}-1}}$$

(4)

where y_i refers to the yield for year i, and n is the number of the studied years of production (in our case, n = 9).

The total annual dry matter produced every year was estimated as the sum of dry yield and dry pruning weight. The proportion of yield in the total dry matter was then calculated.

Yearly data were grouped into two stages, including young trees when they were still forming isolated canopies (2014–2016) and adults that formed a continuous hedgerow (2017–2022). In each group of data, an analysis of variance was performed to test the cultivar effect of canopy increment, pruning volume, pruning weight, TCSA, yield, fruits per tree, bearing index, and total biomass. The total biomass annually produced by the trees’ aerial part was estimated by summing up the yield (reproductive) and pruning weight (vegetative), both on a dry basis. Pearson correlations among those parameters were calculated for each year (from 2017 to 2022) using average yearly values for each cultivar. Then, the values of all years’ correlations were averaged. Finally, the distribution of the total pruning weight was calculated among the topping, lateral young, and lateral old branches, and among branches and leaves.

3. Results

High variability was observed for all the traits measured in this cultivar trial. Cultivar had a significant effect both on young (2014–2016) and adult (2017–2022) tree stages (

Table 1. Average accumulated values of the agronomic traits measured in this comparative trial in young (2014–2016) and adult (2017–2022) trees per cultivar. Initial canopy is the canopy volume measured in December 2014 before the first pruning. Different letters indicated significant differences among cultivars’ means.

	Cultivar	Initial Canopy Vol (m3/ha)		Average Canopy Vol Incr (m3/ha)		Accumulated Pruning vol (m3/ha)		Accumulated Fresh Pruning Weight (kg/ha)		Average TCSA * Incr (cm2)		Accumulated Yield (kg/ha)		Bearing Index		Average Yield as % of Dry Mater
2014–2016	Arbequina	2987.8	b	6671.6	a	2645.4	ab	1629.7.	a	11.2	ab	32,844.3	ab			69.5.	b
	Arbosana	1804.5	cd	4030.5	cd	1205.7	c	450.9.	b	7.0	c	33,930.5	a			85.9.	a
	Koroneiki	2545.7	b	5612.3	ab	2254.6	ab	1428.5.	a	11.4	a	33,421.9	ab			70.7.	b
	Lecciana	3753.5	a	6830.6	a	3061.7	a	1478.5.	a	9.1	bc	32,603.5	ab			67.2.	b
	Oliana	1352.2	d	3116.6	d	934.0	c	529.2.	b	4.5	d	27,368.6	ab			86.0.	a
	Sikitita	2012.3	c	5096.3	bc	1778.8	bc	1135.9.	ab	10.1	ab	25,787.3	b			81.8.	a
2017–2022	Arbequina			33,077.7	a	28,477.4	a	64,620.8.	a	57.9	ab	70,709.9	ab	0.20	b	43.9.	c
	Arbosana			19,398.0	bc	16,567.8	bc	35,991.3.	bc	43.4	c	83,331.8	a	0.19	b	62.6.	ab
	Koroneiki			31,428.2	a	26,893.2	a	70,414.3.	a	66.8	a	64,450.4	b	0.24	b	42.6.	c
	Lecciana			24,602.6	b	20,714.0	b	60,694.2.	a	52.0	bc	66,037.8	b	0.70	a	40.1.	c
	Oliana			14,760.4	c	12,643.6	c	21,983.6.	c	24.9	d	78,208.8	ab	0.15	b	71.8.	a
	Sikitita			21,127.2	b	18,945.9	b	38,323.0.	b	51.9	bc	73,493.5	ab	0.18	b	57.5.	b

* TCSA = trunk cross-sectional area.

). Block variance was 5- to 10-fold less than the cultivar factor for most of the traits measured. Differences in tree growth were higher in young trees, with ‘Lecciana’, ‘Arbequina’, and ‘Koroneiki’ showing the highest values for accumulated canopy increment, pruning volume, and fresh pruning weight. Those differences were already reflected in the initial canopy volume measured before the first pruning. In adult trees, ‘Arbequina’ and ‘Koroneiki’ showed the highest values for accumulated volume increment and pruning volume, including also ‘Lecciana’ for cumulative fresh pruning weight. For TCSA, ‘Oliana’ showed the lowest values from 2015 (Figure 1), followed by ‘Arbosana’. ‘Koroneiki’ had the highest TCSA during all the experiment, which was similar to that of ‘Lecciana’ and ‘Sikitita’.

Among the productivity traits, accumulated yield showed few differences among cultivars (Table 1); only ‘Koroneiki’ and ‘Lecciana’ showed significantly less yield than ‘Arbosana’. The bearing index estimates the irregularity of interannual productivity in the adult stage. In general, it was low, mainly due to stable productivity until 2019. However, more irregular productivity was observed from 2020 to 2022 (Figure 2). This could be associated with high summer temperatures in those years but also with the higher age of the hedgerow and more competition among neighboring trees. The exception is ‘Lecciana’, which showed a marked alternate bearing during all the years under evaluation.

Yield represented a higher percentage of total biomass in young than in adult trees (Table 1). Both in young and adult ‘Oliana’, ‘Arbosana’, and ‘Sikitita’ trees, yield represented a higher percentage of total biomass than in the other three cultivars.

A high average positive correlation was found between pruning weight (both in dry and fresh basis), pruning volume, and canopy increment in the previous year (

Table 2. Pearson correlations (r values) among the agronomic traits measured in this comparative trial in adult (2017–2022) trees. Average values of correlations per year are indicated.

	Pruning Volume+1	Fresh Pruning Weight+1	Dry Pruning Weight+1	Canopy Increment	TCSA **	TCSA Increment	Yield
Fresh pruning weight+1 *	0.85  ***
Dry pruning weight + 1	0.81	0.97
Canopy increment	0.99	0.86	0.84
TCSA	0.80	0.80	0.75	0.82
TCSA increment	0.45	0.57	0.53	0.51	0.82
Yield	−0.54	−0.41	−0.34	−0.46	0.14	−0.03
Yield as % of dry mater	−0.86	−0.89	−0.87	−0.85	0.15	0.01	0.69

* “+1” indicates values for the next year’s measurements. ** TCSA = trunk cross-sectional area. *** Values higher than 0.8 are highlighted in bold.

). All those parameters were negatively correlated with the proportion of yield with respect to all the biomass generated each year. Moreover, TCSA showed a high correlation with canopy increment and pruning weight. It is interesting to notice that the initial canopy volume measured in January 2015 (before the first pruning) was correlated with the average pruning weight for 2017–2022

‘Koroneiki’, ‘Arbequina’, and ‘Lecciana’ showed the highest pruning weight almost every year (Figure 3). In those three cultivars, top pruning also represented a higher proportion of total pruning than in the other three cultivars in both young and adult trees (Figure 4). In the meantime, ‘Arbequina’ and ‘Koroneiki’ showed the highest proportion of old lateral branches in young trees. In adult trees, ‘Oliana’ had a lower proportion of old lateral branches than the rest.

The proportion of total pruning weight on a dry basis, corresponding to stems and leaves, was very similar in all cultivars and in both young and adult trees (Figure 5A,B). Only ‘Koroneiki’ showed a slightly higher proportion of leaves than the rest of the cultivars. Those percentages also showed similar values (Figure 5C,D) in the three groups of pruning materials (top pruning and young and old lateral pruning).

4. Discussion

One of the main constraints on olive cultivars to be suitable for hedgerow growing systems is training them in a way that can be harvested by straddle machines, while still allowing for a high and stable olive yield with the pruning needed for this training [3]. The six cultivars evaluated in the present comparative trial were initially considered suitable for this growing system [1]. In fact, ‘Arbequina’, ‘Arbosana’, and ‘Sikitita’ were reported to have lower vigor than other traditional cultivars when trained in hedgerows [6,17,18]. However, a high pruning volume was observed for all cultivars, especially in the adult period. This reinforces the idea that pruning is a critical operation for the long-term viability of this growing system [1] and that cultivars with low pruning needs but with high and stable productivity are needed.

However, significant differences in canopy growth, pruning needs, and yield stability were observed among the six cultivars tested. Initial canopy volume, measured three years after planting, already reflected the differences in canopy volume and pruning weight observed 9 years later. This indicates that the early measurement of canopy volume, before any pruning has been performed, might be an interesting tool for selecting low-vigor genotypes. ‘Oliana, ‘Arbosana’, and ‘Sikitita’ showed the lowest values, while ‘Koroneiki’, ‘Arbequina’, and ‘Lecciana’ were the cultivars with higher vigor, as previously reported [9], and with higher pruning weight. However, in a trial in Sicily, southern Italy, ‘Arbequina’ and ‘Oliana’ showed the same canopy volume in unpruned trees, which was higher in ‘Arbosana’ [2]. Those differences among trials might be attributable to different environmental conditions and planting densities. The likely environmental influence on vigor indicates that the evaluation performed here should be conducted in other environments to fully characterize those cultivars.

A high genetic effect on vigor was also found in seedlings of breeding programs in the early [19] and late selection stages [20]. However, in cultivar trials in the hedgerow system, plant vigor has received little attention despite its importance in determining the suitability for mechanical harvesting. This could be due to the difficulties of properly measuring canopy volume in large continuous hedgerows. New measurement techniques, such as the ones associated with unmanned aerial vehicles (UAVs), could boost the measurements of volume and canopy traits in hedgerow olives both in experimental trials [21] and in commercial orchards. The high correlation between pruning weight and pruning volume reported here indicates that the pruning needs of a cultivar could be estimated very well by UAV volume measurements [22]. In hedgerow olive orchards, as in the one in this work, plants are trained to form a hedgerow with fixed dimensions to allow the straddle harvester to pass over [1]. Therefore, canopy volume is not a good estimation of cultivar behavior. The results obtained here indicate that other parameters, such as yearly canopy increment and pruning weight, should be used to test growing differences among cultivars.

Not only the total pruning weight but also the composition of the pruning materials seems to vary across cultivars. ‘Koroneiki’, ‘Arbequina’, and ‘Lecciana’ showed the highest top pruning weight, indicating that those cultivars might have a higher upright growth habit. Old lateral branches were more frequent in ‘Arbequina’ and ‘Koroneiki’. The low proportion of “old lateral branches” in ‘Oliana’ might indicate that its structure is based on very small, weeping branches. An association between low vigor and low proportion of old woody structures was previously reported [12]. However, this lack of sufficient branching structure could be a problem in long-term trees with high yields. ’Oliana’ was previously reported to have thinner and shorter shoots and a higher branching frequency than ‘Arbequina’ and ‘Arbosana’ [2]. All this is important since pruning is the costliest operation in hedgerow orchard management [22], and even more so considering that the pruning of different parts of the hedgerow (top and lateral) and different types of materials (old and young shoots) could have different costs. The proportion of leaves to stems in the total pruning weight was around 40–60% for all cultivars, both on a dry and wet basis. This proportion is similar to what was reported for 4-year-old ‘Arbequina’ and ‘Frantoio’ potted plants [13].

TCSA also showed significant differences among cultivars and a relatively good correlation with canopy volume, as previously reported [23], and also with pruning weight. Therefore, it can be considered a complementary, easy-to-use criterion for selecting cultivars for high-density orchards [12]. However, this parameter should be taken with caution, as there are some exceptions to the good TCSA/canopy volume correlation. In this work, ‘Sikitita’ had one of the highest TCSA increments, but the canopy increment and pruning weight were not so high. A lack of correlation between trunk size and canopy volume was previously found in a hedgerow cultivar trial [24].

Contrarily to vigor, little variation among the cultivars was observed for cumulated yield. Few differences in yield were also reported in a trial in Toledo, central Spain, for the same set of cultivars, except ‘Lecciana’ and ‘Oliana’ [6]. Therefore, it seems that increasing yield in breeding programs may be a difficult task, while selection for lower pruning needs could be achievable, although more experiments are needed to confirm that.

Furthermore, yield also showed high stability (low alternate bearing) across years for all cultivars except ‘Lecciana’. This is despite the high variability in rainfall and temperature observed over the 9 years of this study. The lower yields in 2020 and 2022 with respect to previous years could be explained by the high summer temperatures reported in those years, but also by the fact that the hedgerow was growing older. ‘Koroneiki’ was previously reported to have a high tendency for biennial bearing in Cordoba, southern Spain [25], and in the previously mentioned Toledo trial, ‘Arbosana’ and ‘Sikitita’ showed less alternate bearing than ‘Arbequina’ and ’Koroneiki’. These differences in alternate bearing between experiments might be due to climatic differences that promote differences in growth rate among the cultivars. Other traditional cultivars tend to have higher alternate bearing than those used here, probably due to their higher vigor and pruning needs [18].

In fact, this alternate bearing could be directly related to the distribution of total annual biomass production between fruits and vegetative growth. In our case, ‘Oliana’, ‘Arbosana’, and ‘Sikitita’ were the cultivars with the highest proportion of fruit in the total biomass, at around 60–70%, while ‘Arbequina’, ‘Koroneiki’, and ‘Lecciana’ showed the lowest values. These differences were already observed in young trees, even before the first pruning. Therefore, it seems that an early selection for this parameter could also be performed in comparative breeding trials. A similar proportion of fruits with respect to vegetative biomass was previously reported for ‘Arbequina’ in Spain [26] and in Italy [13]. However, in the Spanish work, the proportion of stems in the vegetative biomass was 70%, a bit higher than in our case. This is probably due to the vase-shape training in that work, different from the hedgerow formation in the present one. A higher proportion of vegetative biomass with respect to fruits than the one reported here was found in ‘Leccino’ and ‘Racioppella’ potted plants [14]. Both of them are considered to be more vigorous [27] and to have a later bearing than the ones evaluated here. This supports the idea that early bearing and biomass partitioning are linked to lower vigor across olive cultivars, as previously stated [28].

Therefore, low-vigor cultivars might have the advantage of better suitability for hedgerow formation, but also fewer pruning needs, a higher proportion of fruits with respect to total biomass, more stable productivity across years, and earlier bearing. However, this behavior may vary with different locations, fertilization, and/or irrigation management, as mentioned above for the trial performed in Sicily. Even planting density could affect growth behavior [29]. In particular, hedgerow growing in dry farming might produce a different growth rate than the one reported here. Therefore, multi-environment trials should be considered to fully understand the cultivars’ differences. Additionally, other traits such as oil content and composition and resistance to pests and diseases should be considered before determining the most suitable cultivars for a given set of environmental conditions.

5. Conclusions

In summary, a high proportion of yield with respect to vegetative biomass is necessary for a cultivar to be adapted to hedgerow growing system. It seems that this characteristic can be estimated in young cultivar trials before any pruning is made. It is critical to have low pruning needs and low biennial bearing. On the contrary, TCSA as an indicator of low vigor cultivars should be interpreted with caution, considering the data on ‘Sikitita’ observed here. In the climatic conditions of this experiment, ‘Arbosana’, ‘Sikitita’, and ‘Oliana’ seem to be the cultivars with the best balance of vegetative growth and productivity. However, different cultivars’ behavior could be optimized by adapting planting density, pruning, irrigation, and fertilization strategies.