Hedgerow Olive Orchard Research Articles

Hedgerow Olive Orchards versus Traditional Olive Orchards: Impact on Selected Soil Chemical Properties

Olive orchards cover over 10 million hectares worldwide, with production techniques undergoing significant changes in the past three decades. The traditional rainfed approach, involving minimal inputs, has given way to irrigated super-intensive systems with higher planting density, increased productivity, a greater use of fertilizers and phytopharmaceuticals, and total mechanization. Its impact on soil chemical properties remains a topic of great debate, and no definitive consensus has been reached. Our main objective was to examine the different effects of traditional olive orchards and super-intensive orchards on soil chemistry over a decade. We collected and analyzed 1500 soil samples from an irrigation perimeter in southern Portugal in 2003 and 2013. Our findings indicate that, compared to traditional olive orchards, super-intensive ones show, in a decade, a significant decrease in soil organic matter (less 22.8%—p < 0.001), namely due to the increase in mineralization caused by an increase in soil moisture content as a result of irrigation practice, and an increase in sodization (more 33.8% of Ext Na—p < 0.001) highlighting the importance of monitoring this factor for soil fertility. In comparison to other irrigated crops in the region, super-intensive olive orchards promote a significant soil acidification (from 7.12 to 6.58), whereas the pH values of the other crops increase significantly (3.3%, 13.5%, and 3.0% more in corn, tomato, and cereals, respectively). Mainly because of the decrease in organic matter levels with soil acidification and soil sodization, we can underline that hedgerow olive orchards can affect soil characteristics negatively when compared with traditional ones, and it is necessary to adopt urgent measures to counter this fact, namely sustainable agriculture practices.

Transpiration by sap flow Thermal Dissipation Method: applicability to a hedgerow olive orchard

The climate change requires thrifty use of water resources in agriculture since irrigation is became common also for those crops like olive orchard that were traditionally grown in rainfed conditions. The water requirement is imperative in semi-arid conditions of the Mediterranean basin especially if the olive orchards are cultivated in super high density. For a correct irrigation scheduling, methods to measure transpiration (Tr) at plant level are used. Among the most spread methods to determine Tr, the thermal dissipation method (TDM) has been applied on a hedgerow olive orchard considering: (i) species-specific local calibration, (ii) wound effects, (iii) azimuth correction, and (iv) radial gradient corrections. The performances of the corrected TDM method have been evaluated with respect an independent method, the water balance at weekly scale. If any correction nor specific calibration is carried out, the underestimation of the actual transpiration calculated by TDM was of about -18% with respect to the water balance method.

Direct and indirect ground estimation of leaf area index to support interpretation of NDVI data from satellite images in hedgerow olive orchards

In discontinuous crop soil coverage condition, as for many horticultural crops (e.g. fruit or olive orchard), the low spatial resolution of freely available reflectance data acquired from satellites, affects their agronomic use. Each reflectance pixel value is influenced not only by the reflectance response of the target crop but also by the percentage of pixel covered by the crop, as bare soil and/or spontaneous vegetation strongly affects whole pixel reflectance.In this context, when the analysis of crop conditions is the main agronomical target, the measurement of Leaf Area Index (LAI), supporting the estimation of the area covered by the discontinuous crop, could represent a crucial step helping the interpretation of remote sensed spectral data including related vegetation indices.From this perspective, a field experiment has been conducted on an 8.30 ha super intensive hedgerow olive orchard, monitoring (i) variation of NDVI from an 830 pixels’ grid of the Sentinel-2 imagery (10×10 m) during two years (2020–2021); (ii) LAI estimated by destructive measurement, and (iii) LAI estimated by light transmittance at soil level under the crop measured by a commercial low cost field instrument (LAI-Pen LP 100) with two light sensors (400 - 700 nm and 400 - 500 nm bands).Mean NDVI elaborated from Sentinel-2 imagery and referred to the whole orchard, varies from 0.28 to 0.81, along the two years, and was quite stable during the summer months for each year (0.28–0.36 in 2020 and 0.39–0.41 in 2021). LAI estimated by destructive measurements on single plants, ranged between 2.17 and 4.38. LAI estimated by LAI-Pen, was strongly related to LAI estimated by destructive measurements (R2=0.9473 n = 9)Finally, the average of LAI-Pen measurements referred to all the plants (n = 16) included in each pixel of the Sentinel 2 measurements’ grid, resulted directly correlated to pixel NDVI values collected in the same date.

Decoupling factor, aerodynamic and canopy conductances of a hedgerow olive orchard under Mediterranean climate

The degree of coupling between canopy and atmosphere, through the decoupling factor Ω, well describes the behaviour of a crop concerning its water use and carbon dioxide exchange. Super high-density hedgerow olive orchard system is in great expansion all over the world and, since it has a complex field structure in rows of adjacent trees, investigations are necessary to assess the Ω patterns, as well as aerodynamic (ga) and canopy (gc) conductances in different water conditions. In this study, in a hedgerow olive orchard (cv. “Arbosana”) submitted to full (FI) and regulated deficit irrigation (RDI), cropped under a Mediterranean semi-arid climate (southern Italy), Ω has been determined using gc, as deduced by inverting the Penman-Monteith equation, and ga, by upscaling the wind speed measured in a close station to the canopy; the transpiration has been measured by sap flow thermal dissipation method. The results showed that this olive orchard results very well coupled to the atmosphere, in any soil water conditions; Ω is generally very low, being during daytime equal in mean to 0.021±0.003 ms-1 and 0.018±0.004 ms-1 for RDI and FI, respectively. This condition is linked to ga and gc values; in fact, canopy conductance is much smaller than the aerodynamic one in any water and climatic conditions, except when all canopy surfaces are saturated in water. In this latter case, the gc assumes the highest values due to the contribution of the part of conductance attributable to the structure of the orchard.

Managing Water Stress in Olive (Olea europaea L.) Orchards Using Reference Equations for Midday Stem Water Potential

The irrigation surface of olive orchards has increased over recent decades. In zones affected, deficit irrigation scheduling is a must. The aim of this work was to study water stress management based on reference equations for midday stem water potential. An experiment was conducted over three seasons in Seville (Spain) from 2020 to 2022. A young hedgerow olive orchard (cv Manzanilla de Sevilla) was irrigated using three different treatments: Control (full irrigated), RDI, and Rainfed, in a completely randomized design (six replications). The midday stem water potential and leaf conductance were measured throughout the three seasons. Stem water potential was more sensitive to water stress than leaf conductance and showed a clearer impact and rehydration. Individual data of stem water potential were grouped according to leaf conductance reduction. The relationship of these stem water potentials and temperature or vapor pressure deficit was significant, linear, and aligned to published baselines. Scattering in these equations increased when the leaf conductance reduction was greater. These reference equations would be useful to define moderate water stress conditions in the most sensitive processes, such as vegetative or fruit growth. Definition of severe water stress conditions would be better established with constant values.

Methodology of stem water potential measurement on hedgerow olive orchards

Aim of study:To evaluate the effect of leaf covering, leaf position, leaf age, time and sample size in measurements of stem water potential (Ψstem) in olive hedgerow orchards. Area of study: The experimental orchards were located in the Centre of Spain (Toledo) Material and methods: Midday Ψstem was measured using a pressure chamber in two super-intensive olive hedgerow orchards subjected to various water status. Main results: Measurements were taken at solar noon on shaded leaves at mid canopy height following at least 1 hour of covering. Such measurements on 5 trees were sufficient to define the water status of individual homogeneous irrigation blocks. This combination of techniques is essential for repeatable measurements of Ψstem required to establish critical irrigation points and manage deficit irrigation strategies seeking to control vegetative growth and reduce water use with minimal effect on oil yield in olive hedgerow orchards and maximum oil quality. Part of our results weren’t previously reported: 1) Covering leaves with aluminium doesn’t completely stop transpiration and leaves must be covered and located in the shaded part of the canopy. 2) Ψstem depends on leaf height on olive hedgerow. 3) Ψstem of young leaves was less variable than in older ones. 4) Ψstem at solar noon presented larger differences with previous hours than later. Research highlights: Leaves for measurements of stem water potential must be previously covered and located in the middle height of the shaded part of the canopy.

Detection of Ecballium elaterium in hedgerow olive orchards using a low-cost uncrewed aerial vehicle and open-source algorithms.

Ecballium elaterium (common name: squirting cucumber) is an emerging weed problem in hedgerow or superintensive olive groves under no tillage. It colonizes the inter-row area infesting the natural or sown cover crops, and is considered a hard-to-control weed. Research in other woody crops has shown E. elaterium has a patchy distribution, which makes this weed susceptible to design a site-specific control strategy only addressed to E. elaterium patches. Therefore, the aim of this work was to develop a methodology based on the analysis of imagery acquired with an uncrewed aerial vehicle (UAV) to detect and map E. elaterium infestations in hedgerow olive orchards. The study was conducted in two superintensive olive orchards, and the images were taken using a UAV equipped with an RGB sensor. Flights were conducted on two dates: in May, when there were various weeds infesting the orchard, and in September, when E. elaterium was the only infesting weed. UAV-orthomosaics in the first scenario were classified using random forest models, and the orthomosaics from September with E. elaterium as the only weed, were analyzed using an unsupervised algorithm. In both cases, the overall accuracies were over 0.85, and the producer's accuracies for E. elaterium ranged between 0.74 and 1.00. These results allow the design of a site-specific and efficient herbicide control protocol which would represent a step forward in sustainable weed management. The development of these algorithms in free and open-source software fosters their application in small and medium farms. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Yield response of a mature hedgerow oil olive orchard to different levels of water stress during pit hardening

Drought sensitivity in olive trees varies throughout the season. The yield response to drought needs to consider the final use of the fruits and harvest date. In Mediterranean climates, the oil accumulation tends to occur in a period of low evaporative demand and during the rainy period. The aim of this work was to evaluate the effect of water stress during pit hardening on the yield components of oil olive trees. The experiment was conducted during three seasons (2017–2019) in a mature hedgerow olive orchard (11 years-old, Arbequina cv). The experiment design was a randomized completed block with 4 repetitions of 4 different irrigation treatments. Treatments were: Control, no water stress throughout the season; Regulated deficit irrigation (RDI)-1, moderate water stress during pit hardening and total recovery after the last week of August; RDI-2, same as RDI-1 but with severe water stress and partial recovery; and sustained deficit irrigation (SDI), constant applied water rate and the same seasonal water than RDI-2. The irrigation scheduling in RDIs were based on the frequencies of the trunk growth rate. No significant differences were found in fruit and oil yield between treatments. There were a significant relationship between water status measurements and fruit and oil yield. Part of the decrease in fruit yield with midday stem water potential (SWP) was related to fruit moisture, as no significant fruit drop was found. Only conditions of water stress in 2017, before the end of endocarp size, were related to a great reduction of fruit volume and, consequently, with fruit and oil yield. The relationship between the percentage of oil in dry weight and SWP was quadratic in different phases. Such relationships could help quantify the water stress level in these periods to maximize oil accumulation.

Long-term effects of row orientation on oil yield and oil yield components of hedgerow olive orchards cv. Arbequina

Orchardists are adopting hedgerow systems of many horticultural tree crops to benefit from early and higher yield and to facilitate mechanical pruning and harvesting for more timely management at lower cost. In the case of olive, guidance in orchard design is available for the dimensions (height and width), spacing and porosity of hedgerows of the dominant super-high density (SHD) design but less so for hedgerow orientation. An analysis is presented of oil yield and its components of four olive hedgerows orchards (N–S, E–W, NE–SW and NW–SE) maintained at optimum dimensions during 7 years from the third year after planting. Oil yield was highly variable from year to year in a range 1.7–3.6 t oil/ha but average yield of NE–SW, although not different from NW–SE and N–S, was significantly greater than E–W by 12%. Yield of NE–SW exceeded those of other orientations in two of the seven years of observation by increase in fruit number without effect on fruit size or oil concentration. Analysis of the impact of orientation on yield excludes annual interception of solar radiation as an explanation because NE–SW has similar interception to NW–SE and N–S but greater yield. This identifies the importance of seasonal, and possibly diurnal, differences in radiation interception and associated microclimatic factors of temperature, VPD and water stress. In olive, determination of fruit number is a long stepwise process that commences in autumn with bud initiation and continues with bud formation, flowering, fruit set and fruit fall in the following spring. Concentration of effort on the role of orchard design and management in determination of fruit number emerges as the most useful step in unraveling the role of hedgerow orientation and yield variability in olive production systems.

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

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.

Spring deficit irrigation promotes significant reduction on vegetative growth, flowering, fruit growth and production in hedgerow olive orchards (cv. Arbequina)

An irrigation experiment was conducted during 5 years in two hedgerow olive orchards (C and L) cv. Arbequina in Central Spain. The control treatments (C1 and L1) were irrigated to maintain the “wetted bulb” near field capacity throughout the season. Three deficit-irrigation treatments were applied from shoot growth (April-May) until pit hardening (beginning of July) with water applications relative to control, C2, C3, C4 (50, 25, 0%) and L2, L3, L4 (40, 17, 0%), respectively. Treatments reverted to full irrigation after pit hardening. During the treatment period a series of phenological events occurs: bud break, shoot growth, flower differentiation, flowering, fruit set, fruit drop and pit hardening. Responses of vegetative growth, flowering, fruiting, fruit characteristics and production were evaluated through their relationships with midday stem water potential (Ψstem). Flowering was shown to be the most sensitive period to deficit irrigation and the major determinant of final production through reductions on fruit number and oil content. With high water during flowering (mean Ψstem before irrigation >−1.0 MPa) trees developed more nodes, leaves, fertile inflorescences and fruits per inflorescence with consequent high production (1278 kg oil ha−1). Oil production was significantly reduced (64% of maximum) when Ψstem was allowed to fall below −1.5 MPa at flowering and was halved at −1.7 MPa, reducing water productivity from 0.26 to 0.21 kg oil m−3. In contrast, Ψstem could be reduced to −1.8 MPa after flowering until pit hardening without effects on fruit drop, fruit size or oil content. Fruit drop increased when Ψstem from flowering until pit hardening was below −2.71 MPa. Fruit oil content at harvest was strongly related with fruit dry weight at pit hardening. Vegetative growth occurred continuously during spring, although mainly during flowering, and could not be reduced by deficit irrigation without reducing production. The results are advantageous to irrigation management in this and similar climatic regions where Spring is a critical period for olive production due to variable temperature, rainfall and crop water demand. They establish the high thresholds of Ψstem required to guide irrigation management during Spring without yield loss, and the substantial resulting loss when this threshold is exceeded. They also reveal that deficit irrigation strategies cannot be used in Spring to control canopy size in hedgerow orchard without serious impact on yield.

Long-term effects of row spacing on radiation interception, fruit characteristics and production of hedgerow olive orchard (cv. Arbequina)

In 2008, two experimental plots, oriented NS and EW, respectively, were established in Puebla de Montalbán, Toledo, Spain, at seven row spacings: 2.5, 2.75, 3.25, 3.75, 4.25, 4.75 and 5.0 m, all with same intra-row spacing of 1.3 m. Fruit characteristics (number, size and oil concentration) and an alternate bearing index were evaluated during years 3–11 after planting. Incident and intercepted canopy radiation were simulated with a mathematical model.During the first three harvests, fruit characteristics and oil production/tree were not significantly affected by row spacing such that both fruit and oil production/ha were directly related to tree density per ha. Subsequently, individual trees in the closer-spaced hedgerows developed fewer fruits (56 %), larger fruits (15 %) with greater oil concentration (3 %) than the more-spaced trees providing a partial compensation of fruit and oil production/ha. During 8–11 years after planting, when all hedgerows had similar structure, fruit (R2 = 0.86–0.93) and oil (R2 = 0.79–0.92) production/tree were strongly and linearly related to row spacing with differences between orientations that decreased markedly as spacing increased. Whereas fruit production/ha (R2 = 0.97–0.98) retained a linear response across all row widths, oil production/ha remained constant at the three closest spacings (2.50–3.25 m), then decreasing linearly (R2 = 0.84–0.98) to the widest spacing. Differences in oil yield between orientations at close spacing (2.9 and 2.5 t/ha, EW and NS, respectively) were lost at the widest spacing.Fruit but not oil production per orchard area was linearly related with spacing and intercepted radiation. A reduction of 1 m of spacing from 5.0 to 3.25 m increased interception by 12 % and oil production by 0.32 and 0.48 t oil/ha in NS and EW, respectively. When data from the two orientations were normalized and pooled in a single relationship, oil production increased linearly (R2 = 0.89) with interception to a maximum of 65 % (reached in spacing 3.6 m in NS and 3.3 m in EW) of incident radiation revealing the impact of lower transmission of radiation within closely spaced hedgerows.

Spring deficit irrigation in olive (cv. Genovesa) growing under arid continental climate: Effects on vegetative growth and productive parameters

This study was aimed to evaluate the effect of regulated deficit irrigation (RDI), applied from mid-spring to early summer, on physiological parameters, vegetative growth and productivity in an intensive hedgerow olive orchard located in a non-traditional (marked winter-spring water-deficit) olive growing region. The experiments were carried out during three crop seasons by using four years old (7 m × 3.5 m) ‘Genovesa’ olive trees. Three RDI treatments (T25, T50 and T75) were applied as a percentage of crop evapotranspiration (25, 50 and 75% ETc, respectively) during the period from fruit set to pit hardening. Also, a control treatment was irrigated at 100% ETc during the whole crop season. Under the analyzed environmental conditions, stomatal conductance was less sensitive in young leaves than in mature leaves against changes in water availability. This fact should be considered when being used as benchmarks in olives trees submitted to water deprivation during periods with marked water constraint. Regarding vegetative parameters, significant reductions in apical vegetative shoot growth, trunk cross-sectional area and canopy volume were found in less irrigated treatments (T25 and T50) with respect to most irrigated ones (T75 and T100). Moreover, the strongest effects of deficit irrigation were observed when pruning was applied at the end of the second crop season evaluated. Both fruit and oil yields were barely affected by water availability. Although in the first crop season evaluated the fruit yield was greater in the full-irrigation treatment – which could be due to the age of the olive trees -, at the end of the whole experimental period (three crop years) the mean values from this yield component did not present significant differences among all irrigation treatments. Similarly, water availability did not affect oil yield (kg/ha); no significant differences were found among irrigation treatments in any of the crop seasons analyzed. The effects of water availability on productive parameters were more evident when analyzed as an estimated productive response; the total water productivity, calculated on both fruit weight and oil weight bases, gave the highest values in the most restrictive irrigation treatment. Overall, findings from this study could be of interest for olive cultivation in regions with dry spring period and for intensive hedgerow orchards suited to over-row harvesters. Imposing water restriction during this period could be suitable for achieving sustainable fruit and oil productivity while saving considerable amount of irrigation water.

Automatic Irrigation Scheduling on a Hedgerow Olive Orchard Using an Algorithm of Water Balance Readjusted with Soil Moisture Sensors

Recent technological advances have made possible automated irrigation scheduling using decision-support tools. These tools help farmers to make better decisions in the management of their irrigation system, thus increasing yields while preserving water resources. The aim of this study is to evaluate in a commercial plot an automated irrigation system combined with remote-sensing techniques and soil mapping that allows the establishment of regulated deficit irrigation (RDI) strategies. The study was carried out over 3 years (2015–2017) in a commercial hedgerow olive orchard of the variety ‘Arbequina’ located in Alvarado (Extremadura, Spain). An apparent electrical conductivity (ECa) map and a normalized difference vegetation index (NDVI) map were generated to characterize the spatial variability of the plot and classify the zones in homogeneous areas. Then, reference points were selected to monitor the different irrigation sectors. In 2015, the plot was irrigated according to the farmer’s technical criteria throughout the plot. In 2016 and 2017, two different areas of the plot were irrigated applying an RDI strategy, one under expert supervision and the other automatically. The results show that in a heterogeneous plot the use of new technologies can be useful to establish the ideal location for an automatic irrigation system. Furthermore, automatic irrigation scheduling made it possible to establish an RDI strategy recommended by an expert, resulting in the homogenization of production throughout the plot without the need for human intervention.

Long-term evaluation of growth and production of olive cultivars in super high-density orchard under cold-weather conditions

Hedgerow olive orchards are being established in all olive-producing countries. Little information is available, however, concerning adaptation of olive cultivars to cold conditions. For this reason, nine olive cultivars were trained in hedgerows and evaluated during nine years in the cold area of central Spain (Toledo). Three of them (‘Arbequina’, ‘Arbosana’ and ‘Koroneiki’) are the most widely cultivated in hedgerow orchards. ‘Cobrançosa’, ‘Cornicabra’ and ‘Manzanilla cacereña’ are cultivated in cold weather conditions, and ‘Sikitita’ is a new cultivar, so far evaluated only in warm areas. Vegetative growth (tree height and trunk diameter) was measured annually until individual hedgerows were formed. In most cultivars, hedgerows that occurred by the 5th year after planting. At that time, hedgerow architectures were described. Fruits were machine-harvested from the 3rd year. ‘Koroneiki’ showed the highest growth rate from the first year and very few trees were damaged by harvesting. In the 7th year, the most vigorous cultivars were ‘Koroneiki’, ‘Arbequina’ and ‘Cornicabra’ and the least were ‘Arbosana’ and ‘Sikitita’. Regarding hedgerow architecture, ‘Koroneiki’ and ‘Arbosana’ hedgerows were narrow while ‘Arbequina’ and ‘Manzanilla cacereña’ were wide. Neither vegetative growth nor hedgerow size were related with oil production. After 9 years 63% of the ‘Cobrançosa’ trees were severely damaged by harvesting. ‘Arbosana’, ‘Koroneiki’ and ‘Arbequina’ produced the greatest number of fruits and most oil. After 7 years they remained the most productive cultivars but by then oil yields of ‘Cornicabra’ and ‘Sikitita’ were comparable. These latter two cultivars produced fewer fruits of higher oil content. ‘Manzanilla cacereña’ and ‘Cobrançosa’ are not recommended for hedgerow orchards because of high alternate bearing, low production and susceptibility to damage during machine harvesting. ‘Cornicabra’ and ‘Arbosana’ are of questionable use in cold conditions because of high susceptibility to Pseudomonas savastanoi. Considering all agronomic aspects, ‘Koroneiki’, ‘Sikitita’ and ‘Arbequina’ can be recommended for hedgerow production in similarly cold environments.

Using an objective and probabilistic model to delineate homogeneous zones in hedgerow olive orchards

The first stage to implement site-specific crop management (SSCM) within an agricultural field consists in determining subfields of similar production potential, that is, management zones (MZ). Different approaches have been proposed to delineate MZ, but sometimes results are inaccurate and unsatisfactory. In this study, the formulation of the Rasch measurement model, as an objective method which synthesizes data with different units into a uniform analytical framework, is considered to calculate measures of production potential at some locations of an olive orchard. Later, they can be used to delimit MZ.With the aim of illustrating this approach, nine soil properties (soil apparent electrical conductivity, clay, sand, and silt content, organic matter, total nitrogen, available phosphorous and potassium, and cation exchange capacity) measured from soil samples taken at 40 locations in a field were considered. The main results, after applying the Rasch model, were a ranking of all locations according to the soil production potential and another one in which the influence on the production potential of each individual soil property is shown. Moreover, those soil samples or properties which have any anomaly where highlighted; this information can be necessary to conduct site-specific treatments, leading to a more cost-effective and sustainable field management. Additionally, estimates using geostatistical algorithms were utilised to map soil production potential and to delineate with a rational basis the MZ in the field.

Toward the valorization of olive (Olea europaea var. europaea L.) biodiversity: horticultural performance of seven Sicilian cultivars in a hedgerow planting system

An intense survey of the Sicilian’s olive growing areas for autochthonous germplasm, mainly represented by centennials olive trees (Olea europaea var. europaea L.) apparently older then III centuries, started at the beginning of the 1980s and resulted in the selection of more than 150 cultivars and accessions. This germplasm was propagated in a nursery, by grafting onto seedlings of Olea europaea L., and planted in an experimental orchard, in an olive district located in the South-west of the Island, where they were evaluated for over 30 years and selected for their early bearing, high and constant productivity, as well as high oil content of the fruits and excellent chemical (oleic acid and phenol content) and organoleptic profile of the oil. This paper reports data on the horticultural performances (production, vigor, crop efficiency and oil quality) of four cultivars (‘Kalat’, ‘Olivo di Mandanici’, ‘Abunara’ and ‘Minuta’), selected within the Sicilian’s autochthonous germplasm trained as 'Free Palmetta' and tested in a hedgerow planting system at three different planting densities: 500, 666 and 1000 trees ha-1. The cultivar ‘Nocellara del Belice’, ‘Cerasuola, and ‘Biancolilla’, widely cultivated in the area where the trial was carried out, were used as references.The outstanding performance of the cultivar ‘Kalat’ at planting density of 1000 trees ha−1, suggests that this cultivar can be a promising choice for the super high density orchards (SHD). The other cultivars tested did not performed as ‘Kalat’ and seem not suitable for SHD planting system due to their high vigor. The hedgerow planting system tested, in the first 6 years of planting, increaseed productivity of all cultivars compared to traditional olive orchard typical of the area where the trial was conducted. This hedgerow olive orchard may represent a valid solution to increase orchard productivity and to reduce harvest costs by mechanization, depending on tree high, with straddle or side by side canopy contact machines. Achieve higher yield and reducing management costs using autochthonous, resilient cultivars, could be a new strategy to counteract climate changes. The unique organoleptic profiles of the oils obtained from the cultivars tested, could improve the offer of tasty, flavored and nutraceutical extra virgin olive oils in the international markets. Results highlight the importance of preserving and valorizing biodiversity to increase productivity and resiliency of agricultural systems, facing continuous, fast and deep social and environmental changes.

Sensitivity of olive leaf turgor to air vapour pressure deficit correlates with diurnal maximum stomatal conductance

Effective study and management of crops and forests would benefit greatly from useful plant-based indicators of the biological controls on evapotranspiration, and particularly stomatal conductance (gs). Given the strong influence of gs on bulk leaf water potential and turgor pressure (P), in vivo measurement of P may provide useful information about diurnal or seasonal dynamics of gs. Moderate plant water stress affects the diurnal dynamics of P as leaf-to-air vapour pressure deficit (D) varies, and these dynamics correlate to gs. Here, we explored relative changes in P in response to changes in D under mild drought conditions, and how these changes are linked to stomatal behaviour, and specifically to diurnal maximum gs (gs,max), one of the best indicators of plant water stress. We monitored ecophysiological and environmental variables, as well as a relative proxy for P, during three consecutive seasons in a hedgerow olive orchard where trees were supplied with different irrigation treatments to create well-watered and moderately water-stressed conditions. Our results demonstrated that the sensitivity of P to D correlated well with gs,max reached by the trees within a range in which variations in gs are the main diffusional limitation to photosynthesis. We further showed that this correlation held under a wide range of meteorological conditions and soil water availability. This turgor proxy measurement, which is much easier to measure than gs, can facilitate the use of gs,max as an indicator of plant water stress and evapotranspiration in agriculture and plant science research.

Effects of water stress on fruit growth and water relations between fruits and leaves in a hedgerow olive orchard

Yield, the final goal in agricultural systems, is highly determined by fruit growth. However, most works on deficit irrigation did not consider the physiology and dynamics of fruit growth. In this study, we explore the effect of water relations between leaves and fruits on fruit growth in well-watered (WW) and water-stressed (WS) trees in a super-high-density olive orchard (cv. Arbequina) over a full irrigation season (June–October of 2017) in southern Spain. Both leaf and fruit water potential were measured, along with pressure-volume curves. Concomitantly, fruit growth and diurnal changes in six fruits of each irrigation treatment were continuously monitored with fruit gauges, which recorded changes in the equatorial diameter of the fruit. Fruit water status and growth were greatly affected by water stress, the latter recovering markedly, following our regulated deficit irrigation strategy. The gradient between leaf and fruit water potential was positive most of the time for both irrigation treatments, and greater for WS than WW trees, which suggests water flow into the fruit. However, we also observed negative fruit growth in WS which, together with the positive gradient, suggests that water flow from the parent plant to the fruit was insufficient to balance fruit transpiration under conditions of water deficit. Although a strong correlation was found between leaf water potential and the amplitude of fruit contraction in WW trees, this relationship did not hold for WS trees, suggesting a progressive decoupling of fruit water status from leaves as water stress progressed. Accordingly, an osmotic adjustment as evidenced by the analyses of pressure-volume curves occurred in WS fruits towards the end of the season. These results indicate that leaf-fruit water potential measurements may not be sufficient to study fruit-leaf water relationships in the canopy; however, fruit gauges may serve as highly useful instruments to understand the water status and daily dynamics of fruit growth.

New approaches for precise irrigation in hedgerow olive orchards

New approaches for precise irrigation in hedgerow olive orchards