Hedgerow Olive Orchard Research Articles

Water status, gas exchange and crop performance in a super high density olive orchard under deficit irrigation scheduled from leaf turgor measurements

We evaluated the suitability of scheduling a regulated deficit irrigation strategy in a hedgerow olive orchard with high plant density from leaf turgor related measurements. Measurements were made for two consecutive years at an olive orchard with 1667 ‘Arbequina’ trees per hectare where we had two deficit irrigation treatments, 45RDICC and 45RDITP, plus a full irrigation as a control. The two 45RDI treatments consisted on applying the same regulated deficit irrigation strategy, aimed to supply a total of 45% of the irrigation needs. The 45RDICC treatment however, was scheduled with the crop coefficient approach, while the 45RDITP treatment was scheduled with an irrigation scheduling approach based on leaf turgor related measurements, first suggested by Padilla-Díaz et al. (2016, Agric. Water Manage. 164:28–37). They worked at the orchard in 2014, and made a preliminary evaluation of the irrigation scheduling approach by comparing 45RDITP versus 45RDICC in terms of irrigation dose and frequency, predawn and midday stem water potential (Ψstem), and the fruit yields of each treatment. In this work, we considered the same variables as well as maximum daily values of stomatal conductance and CO2 net assimilation, the seasonal courses of the number of internodes in current-year shoots, leaf area and oil accumulation in the fruits, and total fruit and oil yields. All those variables were monitored both in 2014 and 2015, and we found no differences between the 45RDITP and the 45RDICC treatments, for any of them. The irrigation amounts applied to each treatment differed occasionally, but the total water supplies were similar to both 45RDI treatments. Our results, therefore, confirm the suitability of the irrigation scheduling approach proposed by Padilla-Díaz et al. (2016) to apply regulated deficit irrigation in commercial hedgerow olive orchards. We found additional evidence for the 15% changes on the irrigation amount recommended by the irrigation scheduling approach as being suitable for the orchard conditions. Caution must be taken when applying this approach to other olive orchards, since the relations between the tree water status and the shape of the daily curves recorded with the ZIM probes may depend on the cultivar and orchard conditions.

Assessing plant water status in a hedgerow olive orchard from thermography at plant level

Water scarcity is the most limiting factor in many irrigated areas of Mediterranean countries such as South Spain. Olive growing has been traditionally associated to rain-fed agriculture, although irrigation and practices related to intensive agriculture have been progressively introduced, requiring a more precise irrigation scheduling to save water. Thermal imaging is among the alternatives to assess the crop water status, especially when deficit irrigation (DI) strategies are applied. However, this technique requires of new advances to be more user friendly and robust for practical usage. The aims of this study were: i) to define threshold values of canopy temperature (TC), Crop Water Stress Index (CWSI) and the temperature difference between canopy and the surrounding air (ΔTcanopy-air) for the assessment of the olive water status when a DI strategy is applied; ii) to define the best time of the day and the best area of the canopy to carry out thermal measurements, and iii) to obtain relationships between thermal indicators and main physiological parameters useful to estimate the crop water status from thermal data. The trial was conducted during 2015, in a hedgerow olive orchard (SW Spain) with 8-year-old trees (Olea europaea L., cv. Arbequina), under three irrigation regimes: a full-irrigation treatment (FI) and two regulated deficit irrigation treatments aimed to supplying 45% of the irrigation needs. In one of them, irrigation was scheduled from leaf turgor pressure related measurements (45RDITP). In the other, the crop coefficient approach was used to schedule irrigation (45RDICC). Significant correlations between Tc versus stem water potential (Ψst) and leaf gas-exchange parameters (stomatal conductance to water vapour, gs; net CO2 assimilation, AN; transpiration, E) were obtained (p≤0.05), in particular from measurements taken at 10:30 GMT in the lower part of the sunlit side of the canopy. Moreover, the relationships between both ΔTcanopy-air and CWSI with the monitored physiological variables were very robust. We concluded that values of ΔTcanopy-air higher than 0°C and values of CWSI up to 0.2 reliably reflect the plant water stress. Our results, therefore, suggest that both ΔTcanopy-air and CWSI measured at midday provide reliable information on the tree water status and are useful to schedule irrigation in hedgerow olive orchards, especially under DI conditions.

Soil moisture dynamics in a hedgerow olive orchard under well-watered and deficit irrigation regimes: Assessment, prediction and scenario analysis

A study was conducted in a hedgerow olive orchard (SW Spain) to assess the capability of the HYDRUS 2D/3D model in predicting seasonal soil water dynamics in a well-watered (full irrigation, FI) and two regulated deficit irrigated plots (60RDI and 30RDI) differing in the timing and level of water stress imposed. The simulated soil water balance components were used to assess the suitability of the irrigation management accomplished in the experimental orchard and that of the irrigation treatments for different soil types and management scenarios. Soil water content (θ) was measured in all four plots per irrigation treatment with two access tubes per plot installed at 0.1m and 0.4m away from the dripper. Comparison of simulated against observed θ showed mean absolute errors ranging from 0.03 to 0.045cm3cm−3, root mean square errors from 0.035cm3cm−3 to 0.056cm3cm−3 and Nash–Sutcliffe efficiency coefficients from 0.438 to 0.834 across all treatments and probe locations. The modelled soil water balance components showed that drainage water losses represented 9–12% only of the applied irrigation water across all irrigation treatments. Scenario analysis revealed that daytime irrigation led to higher drainage water losses in FI than nighttime irrigation. For the same irrigation volumes, rootzone soil pressure head decreased (i.e. became more negative) when the irrigation frequency of the RDI treatments increased, thus supporting the lower irrigation frequencies scheduled in RDI as compared to FI in the experimental orchard. Scenario analysis also revealed the importance of adjusting irrigation schedules to soil type, irrespective of whether FI or RDI treatments were to be implemented.

Scheduling regulated deficit irrigation in a hedgerow olive orchard from leaf turgor pressure related measurements

Regulated deficit irrigation (RDI) has been proposed as one of the most promising irrigation strategies for hedgerow fruit orchards with high plant densities. Scheduling a RDI strategy, however, is highly demanding, since the targeted water savings must be achieved at the same time that episodes of excessive water stress are avoided when the crop is most sensitive to drought. Here we tested an approach to schedule a RDI strategy supplying 45% of the crop irrigation needs, specially designed for hedgerow olive orchards. Our approach is based on the use of a water stress indicator derived from the shape of the daily curves recorded with ZIM sensors, which are related to the leaf turgor pressure. We worked in a mature, fully productive ‘Arbequina’ olive orchard with 1667 trees ha−1, under both a daily irrigated (FI) treatment and the mentioned RDI strategy. We found that the relation between the shape of the curves and the tree water stress levels holds for olive trees of different age under a wide range of growing conditions. We were able to schedule irrigation just from the visual analysis of the curves derived from the ZIM outputs, without any further data processing. A comparison with the crop coefficient approach showed that, with our approach, we achieved greater water savings without affecting neither the trees water status nor the crop performance. Still, further studies are required to confirm whether empirical aspects of our approach are limiting and, if so, to derive suitable alternatives.

Using sap flow measurements to estimate net assimilation in olive trees under different irrigation regimes

The measurement of bulk net assimilation (A) in fruit tree species is hindered by the need for sophisticated and complex instrumentation. The aim of this study is to present a simple alternative for estimating A from sap flow measurements and meteorological records. The proposed method was tested in a mature hedgerow olive orchard of 22.2 ha. Within the orchard, an irrigation experiment was established in a small plot including three treatments: a full irrigated control (CI), regulated deficit irrigation (DI) and a treatment mimicking customary orchard irrigation management (FI). Determinations of sap flow, water potential (Ψ) and trunk diameter variations (TDV) were conducted in the three treatments for 3 years. Also, measurements of net ecosystem exchange (NEE) were performed with an eddy covariance system in the centre of the orchard for the first season. The validity of the method was supported by the fact that estimates of A were consistent with both the measured values of NEE and published data regarding the same species under similar environmental and management conditions. Also, differences in A between irrigation treatments were generally in agreement with irrigation applied, transpiration (E p ), Ψ and TDV. It is concluded that the proposed sap flow-based method represents a user-friendly approach to estimate A at the canopy level with potential to study the effects of DI on biomass accumulation.

Low winter temperatures induce a disturbance of water relations in field olive trees

Low winter temperatures induce an increase in the soil-to-trunk hydraulic resistance of field-grown olive trees resulting in a significant disturbance of their water relations. A disturbance of water relations in response to chilling have long been observed in potted plants growing under controlled conditions, but information is lacking for field plants. The aim of this study was to assess the effects of winter low temperatures on the water relations of mature olive trees. To this end, water potential, sap flux density, soil temperature and meteorological data were monitored in a hedgerow olive orchard near Córdoba, southern Spain, throughout two consecutive winters. Water stress symptoms were found in terms of midday Ψ, despite adequate water supply and low evaporative demand. These effects were associated with changes in the soil-to-trunk hydraulic resistance (R root), which increased by December–January to much higher values than those previously reported in the literature, particularly in the year of higher fruit load. The contribution of viscosity (η) to the observed R root dynamics was almost negligible as deduced from measurements of soil temperature, so the high winter values of R root were likely to have originated from other causes such as reductions in membrane permeability and root growth. The findings of this work raise new major issues that deserve further research such as the impact of the winter water stress on stomatal conductance and photosynthesis rates in mature olive trees.

Effect of varied summer deficit irrigation on components of olive fruit growth and development

The timing, duration, and intensity of summer water restrictions differentially affect overall olive fruit growth and production, based on the underlying fruit developmental processes. For that, the fruit component and tissue morphogenetic response to different irrigation strategies during summer was examined in a hedgerow olive orchard cv. Arbequina. Control trees (CON) were irrigated to maintain the root zone close to field capacity throughout fruit growth. From budburst to 4 weeks after full bloom (WAFB) (Period 1) and from 14 WAFB to harvest (at 23 WAFB) (Period 4) trees of all treatments were irrigated as CON. Two severe water deficit treatments were applied during summer by irrigating 30% CON from 4 to 9 WAFB (Period 2) in DI-P2 or from 9 to 14 WAFB (Period 3) in DI-P3. Moderate water deficit was applied in Periods 2 and 3 by irrigating 50% CON in DI-P2&3. Growth and development of the fruit and its component tissues (exocarp, mesocarp and endocarp), fruit composition, mesocarp cell area and cell number, and epidermal characteristics at the end of each period were evaluated. Water deficits significantly reduced fruit volume at the time when they were applied. Mesocarp size was more sensitive to water deficit than endocarp size and showed a high recovery capacity after rewatering. Although the majority of cells were developed in Period 1, a substantial number of mesocarp cells were also formed later. While mesocarp cell number was unaffected by water reduction in any of the deficit periods, cell size was highly affected but with high recoverability. Endocarp size was reduced when water restriction was applied in DI-P2 and its effect continued until harvest. Fruit oil content at harvest was not significantly affected by the applied water restrictions, whereas water was the fruit component which most responded to both the increases and decreases in irrigation. Cuticle thickness, epidermal cell size and number at harvest appeared to respond to both irrigation regime and fruit expansion pressures.

Phenolic composition of virgin olive oils in cultivars for narrow hedgerow olive orchards

Narrow hedgerows system (NHS) is a new concept of olive orchards characterized by minimum labor requirements, continuous mechanical harvesting, early bearing, high yield, and olive oil quality. In this work, the variability of phenolic composition of virgin olive oils (VOOs) was studied in three cultivars (Arbequina, Arbosana, and Sikitita), two planting systems (NHS: 1975 trees/ha and intensive system (IS): 333 trees/ha) and different harvesting dates (1 October and 26 November for the three cultivars; and three additional dates for the new olive Sikitita: 16 and 29 October; and 12 November). Phenolic compounds were extracted from the obtained VOOs by liquid–liquid extraction with 60:40 v/v methanol/water. The resulting hydroalcoholic extract was analyzed by liquid chromatography – diode‐array detector – fluorescence detection (LC‐DAD‐FD) for individual phenols separation–quantification. Significant differences among genotypes were found for some individual phenols at the first harvesting date. At the second harvesting date, significant differences were found between genotypes and between planting systems (p<0.05). According to the obtained results, the new Sikitita should be harvested at the beginning of the ripening period for obtaining VOO with high phenolic content. Finally, a global agronomic and oil compositional evaluation in NHS of the new cultivars bred specifically is needed for this new olive growing system.Practical applications: Narrow hedgerow is a new very high density (>1500 trees/ha) olive planting system associated to overhead vineyard harvesters that is increasingly used as it reduces drastically both labor and time needed to harvest the crop. This study focuses on the comparison of the content of phenolic compounds in olive oils originated from narrow hedgerow system and intensive system. The results can be used to determine the best time for harvesting the new olive Sikitita, recently selected for narrow hedgerow system, in order to obtain an olive oil with high phenolic content.

A regulated deficit irrigation strategy for hedgerow olive orchards with high plant density

There is not a consensus on the best irrigation approach for super-high density (SHD) olive orchards. Our aim was to design and test a regulated deficit irrigation (RDI) strategy for a sustainable balance between water saving, tree vigour and oil production. We tested our RDI strategy for 3 years in an ‘Arbequina’ orchard with 1,667 trees ha−1. Two levels of irrigation reduction were applied, 60RDI and 30RDI, scaled to replacing 60 % and 30 %, respectively, of the of irrigation needs (IN). We also had a full irrigation (FI) treatment as control, with IN totalling 4,701 m3 ha−1 The 30RDI treatment showed the best balance between water saving, tree vigour and oil production. With a yearly irrigation amount (IA) of 1,366 m3 ha−1, which meant 72 % water saving as compared to FI, the reduction in oil yield was 26 % only. Our results, together with recent knowledge on the effect of water stress on fruit development, allowed us to suggest a potentially improved RDI strategy for which a total IA of ca. 2,100 m3 ha−1 was calculated. Both some management details and the benefits of this suggested RDI strategy are still to be tested.

Summer deficit irrigation in a hedgerow olive orchard cv. Arbequina: relationship between soil and tree water status, and growth and yield components

Stem water potential (Phi-stem) is a useful tool for irrigation scheduling in tree crops, provided threshold values for growth and production are determined for each physiological period. Four irrigation treatments were evaluated in a hedgerow olive orchard. Control (CON) was irrigated using soil water sensors to maintain the root zone close to field capacity. Severe water deficits were applied by irrigating at 30% CON from end of fruit drop to end of July (DI-J) or from end of July until beginning of oil synthesis (DI-A). Less severe water deficit was applied in July and August by irrigating at 50% CON (DI-JA). Continuous measures of soil moisture, Phi-stem and shoot length were recorded in all treatments. Fruit dry weight and oil content were measured at the end of the experimental period and at harvest. Relative extractable soil water to 0.8 m depth (REW) and Phi-stem were highly correlated and influenced by irrigation treatment. Shoot growth, fruit characteristics and oil production were correlated to Phi-stem. Shoot growth was reduced by 50% relative to CON by irrigating at Phi-stem of -1.3 MPa. Fruit dry matter and oil content (g fruit-1) were linearly reduced as mean summer Phi-stem decreased. Oil production was highly related with Phi-stem in August but not in July. Water can be saved in July by irrigating at Phi-stem of -2.9 MPa but Phi-stem should be maintained higher than -2.0 MPa in August to prevent decrease of oil production.

Efeitos da rega e do regime hídrico em olival super intensivo no Alentejo

This study characterizes the effects of a typical farmer irrigation management and one of deficit irrigation imposed to a hedgerow olive orchard (1, 35 x 3,75 m) in the region of Evora, Southern Portugal on a Eutric Cambisol soil (FAO, 1998). The two irrigation regimes and their effects on tree transpiration, soil water content and stem and leaves water potential, a physiological parameter indicator of plant water stress, are analysed. With deficit irrigation DI imposed after pit fruit hardening, it was observed a progressive reduction on the values of tree transpiration, stem and leaf water potential and soil water content predominantly towards the end August and September. For the normal irrigation treatment (FI) transpiration values slightly declined for the months of July and August, although less than the ones for treatment DI. Results obtained with the “big leaf” model of Penman-Monteith (Jones, 1992) and bulk canopy conductance model of Orgaz et al. (2007) indicate that once validated they can be used to predict the transpiration of non-stressed hedgerow olive orchards in Alentejo. Predicting transpiration with the remotely sensed vegetation index NDVI proved difficult for lack of a strong correlation between the two parameters.

Simulation of oil productivity and quality of N–S oriented olive hedgerow orchards in response to structure and interception of radiation

Simulations of oil yield and quality are presented for N–S oriented, hedgerow olive orchards of a range of structures (viz. canopy depth, canopy width, canopy slope and row spacing) using responses of yield and quality parameters to solar irradiance on canopy walls measured in a range of orchards, cv. Arbequina, in Spain. Results reveal that orchard yield of hedgerows of rectangular shape reaches a maximum when canopy depth equals alley width (row spacing−canopy width) and decreases at wider spacing, and/or with wider canopies, as the length of productive row decreases per unit area. Maximum yields for 4-m deep canopies were 2885kgha−1 at 1-m width and 5-m row spacing, 2400kgha−1 at 2-m width and 6-m spacing, and 2050kgha−1 at 3-m width and 7-m spacing. Illumination of canopies can be increased by applying slopes to form rhomboidal hedgerows. Substantial yield advantage can be achieved, especially for wide hedgerows, partly by closer row spacing that increases row length per unit area. By comparison, responses to latitude in the range 30–40° are small and do not warrant different row spacing. Oil quality parameters also respond to orchard structure. Responses are presented for oleic and palmitic acid, stability, and maturity index. Oleic acid content declines as alley spacing increases and is smaller, shallow than in wide, deep canopies. Palmitic acid content, stability, and maturity index increase with row alley spacing and are greater in narrow, shallow than in wide, deep canopies.

Steps toward an improvement in process-based models of water use by fruit trees: A case study in olive

We applied two process-based models in a hedgerow olive orchard with the aim of understanding the limitations and mechanisms behind the control of transpiration in olive trees under drip irrigation. One model is based on the biophysics of water flow through the porous media of soil and xylem. The other is a hydromechanical model based on the observed dependence of stomatal aperture on whole-plant and epidermis water relations. The experiments were made in a hedgerow olive orchard (1667treesha−1) planted with 5-year-old ‘Arbequina’ trees. Measurements were made in control trees irrigated to replace 100% of the crop water needs, and in trees under regulated deficit irrigation (RDI) strategy, in which irrigation replaced ca. 30% of the control. Soil physical properties, root distribution, leaf area, sap flow, leaf osmotic pressure and key variables of leaf gas exchange and water status were measured and models were applied. Results show how in our orchard, with a shallow root distribution and very coarse soil, most of the limitation to transpiration was imposed by the hydraulics of the rhizosphere. The model shows how this limitation was related to the ratio of root to leaf area, and how this ratio can be managed by canopy pruning or by changing the number of drippers. Likewise, osmotic adjustment occurred similarly in both irrigation treatments, despite differences found on leaf water potential. Water stress largely affected plant hydraulic conductivity of RDI trees. A potential involvement of regulating signals, other than purely hydraulics, was evident in both treatments, although our data suggests that these signals were not regulated by the soil water status only.

Assessing water stress in a hedgerow olive orchard from sap flow and trunk diameter measurements

We used sap flow and trunk diameter measurements for assessing water stress in a high-density ‘Arbequina’ olive orchard with control trees irrigated to replace 100 % of the crop water needs, and 60RDI and 30RDI trees, in which irrigation replaced ca. 60 and 30 % of the control, respectively. We calculated the daily difference for both tree water consumption (\( D_{{E_{\text{p}} }} \)) and maximum trunk diameter (DMXTD) between RDI trees and control trees. The seasonal dynamics of \( D_{{E_{\text{p}} }} \) agreed reasonably well with that of the stem water potential. We identified peculiarities on the response \( D_{{E_{\text{p}} }} \) to changes in water stressing conditions, which must be taken into account when using the index. An analysis of the water stress variability in the orchard is required for choosing the instrumented trees. The reliability of the DMXTD index was poorer than that of \( D_{{E_{\text{p}} }} \). The maximum daily shrinkage (MDS) was not a reliable water stress indicator.

Short communication. Harvest time in hedgerow ‘Arbequina’ olive orchards in areas with early frosts

The shortening of harvest time attained in hedgerow olive (Olea europaea L.) orchards represents an advantage for the adoption of this cropping system in areas that are prone to suffer frost during the harvest period. To establish an optimal harvesting window, we carried out a study of the fruit ripening process on a hedgerow orchard of ’Arbequina’ olive trees, located in Zaragoza (Spain). From 2007 to 2009, oil accumulation on the fruit (% of dry weight) and oil yield (grams of oil per 100 fruits) were monitored, from early September to late November. Over the three years both variables peaked around November 15th, indicating that Arbequina reached full ripening earlier than has been reported previously for this variety. In two of the three seasons the orchard suffered several frosts during November. Long term climatic data from this area indicated that the risk of early frosts (<–2°C) increases as November progresses with a high risk after November 20th. In conclusion, the optimal harvesting period for Arbequina in this area should not extend beyond November 20th. A rapid harvesting before this date is advisable to avoid the risk of damage caused by early frost in Zaragoza. Hedgerow planting provides an additional advantage in frost-prone areas, because mechanization of operations permits a short harvest period, easier to fit into the optimal harvesting window.

Online-monitoring of tree water stress in a hedgerow olive orchard using the leaf patch clamp pressure probe

Abstract The need for sophisticated irrigation strategies in fruit tree orchards has led to an increasing interest in reliable and robust sensor technology that allows automatic and continuous recording of the water stress of trees under field conditions. In this work we have evaluated the potential of the leaf patch clamp pressure (LPCP) probe for monitoring water stress in a 4-year-old ‘Arbequina’ hedgerow olive orchard with 1667 trees ha−1. The leaf patch output pressure (Pp) measured by the LPCP probe is inversely correlated with the leaf turgor pressure (>50 kPa). Measurements of Pp were made over the entire irrigation season of 2010 (April to November) on control trees, irrigated up to 100% of the crop water needs (ETc), and on trees under two regulated deficit irrigation (RDI) strategies. The 60RDI trees received 59.2% of ETc and the 30RDI trees received 29.4% of ETc. In the case of the RDI trees the irrigation amounts were particularly low during July and August, when the trees are less sensitive to water stress. At severe water stress levels (values of stem water potential dropped below ca. −1.70 MPa; turgor pressure

Summer deficit-irrigation strategies in a hedgerow olive orchard cv. ‘Arbequina’: effect on fruit characteristics and yield

Maximum production in hedgerow olive orchards is likely not achieved with maximum evapotranspiration over the long term. Thus, regulated deficit irrigation (RDI) should be considered as a management option. Four irrigation treatments were evaluated during the summer, when olive is most drought resistant. Control (CON) was irrigated to maintain the root zone close to field capacity. Severe water deficit was applied by irrigating 30% CON from the end of fruit drop to end July (DI-J) and from end July until beginning of oil synthesis (DI-A). Less severe water deficit was applied during July and August (DI-JA) by irrigating 50% CON. Flowering, fruiting, abscission, fruit development, fresh and dry weight of fruits, and oil production were evaluated. There were not significant differences in number of buds initiated, number of fruits per inflorescence and fruit drop. Oil production was significantly different between irrigation treatments in all experimental years. CON produced more oil and fruit with higher oil % than DI-A and DI-JA. Oil production of DI-J was not significantly reduced compared with CON and oil% was greater. DI-J was the most effective RDI strategy; with 16% less applied water relative to CON. Average loss in oil production of 8% was not significantly different to CON. While DI-JA saved most water (27%), oil production was reduced by 15%. Greatest loss in oil production (21%) was observed in DI-A with water saving of 22%.

Physiological and Growth Responses to Irrigation of a Newly Established Hedgerow Olive Orchard

Olive production in the first few years after planting depends on how the canopy covers the hedgerow and develops flowers. Therefore, optimum irrigation management should look for the minimum amount of water required for maximum growth and bud initiation. The response of a young hedgerow olive orchard to different irrigation strategies was recorded for 3 years after planting in 2003. Observations included stem water potential (Ψstem), leaf conductance (gl), shoot and trunk growth, canopy development, and flowering. During the first year, olives received 74 mm of irrigation. During the second and third years, three irrigation treatments (T2, T3, and T4) were scaled back from a control (T1) that was irrigated to maintain soil close to water-holding capacity. T1 received 56 and 106 mm of irrigation in the second and third years, respectively. Treatments T2, T3, and T4 received 82%, 64%, and 46% of the water applied to T1 in the second year and 76%, 72%, and 29% in the third year of growth, respectively. Trees in T1 displayed different physiological and growth behaviors between years. Ψstem, gl, and shoot growth were 131%, 31%, and 56% lower in the third than in the second year, respectively. Irrigation treatment had no significant effect on evaluated parameters in the second year, except on Ψstem in T4 that fell below that of the other treatments in late September. In the third year, shoot growth, trunk diameter, and leaf area density in T4 decreased 52%, 13%, and 31% compared with T1, respectively. Nevertheless, external surface area and canopy volume were not significantly affected by irrigation treatment. The start of flowering, recorded in the third and fourth years, was not significantly affected by the irrigation received in previous years. Because water stress did not advance flowering, maximum growth should be the main objective in irrigation management of young olive orchards. No differences were observed between T3 and T1 in any of the vegetative, canopy development, or inflorescence parameters recorded, although Ψstem and gl were significantly lower in T3. During the second and third years, T3 can be considered the most efficient irrigation treatment with 36 and 76 mm of irrigation for each year, respectively.

Towards optimal designs for hedgerow olive orchards

An analysis of row height, row width, canopy slope, and alley width of hedgerow olive orchards was conducted to identify combinations that maximise productivity while allowing access to machinery for management. This objective requires maximising both the interception of incident solar radiation and its distribution over the canopy surface for productivity. For maximum productivity, all foliage must be illuminated above threshold values for the critical step in the shoot growth – floral initiation – flowering – fruit formation – fruit filling reproductive sequence. The key sites for adequate illumination are the bases of the canopy walls. For canopies with row height and alley width combinations that provide threshold illumination at the bases of the canopy walls, the area of productive foliage per unit orchard area is inversely related to row width because incident radiation received by broad canopy tops is better spread at smaller irradiance over more canopy wall. The analysis revealed that canopies of equal productivity can be formed with a range of combinations of height, slope, and alley width, and that optimal combinations are responsive to threshold values in the range 20–30% of incident radiation. Research is required to establish threshold values and the limits to row height and row width consistent with year-to-year production of reproductive shoots. The latter requires attention to cost and performance of machinery, the growth habit of the tree, and its response to pruning.