Traditional Olive Groves Research Articles

Agroforestry and the Climate Crisis: Prioritizing Biodiversity Restoration for Resilient and Productive Mediterranean Landscapes

This study deals with the future of the traditional agroforestry systems (TAFSs) in the northern Mediterranean Basin. Important productive systems, such as ancient non-irrigated olive groves and extensive silvopastoral systems, from subalpine grasslands to coastal landscapes, are being irreversibly degraded, threatening the bio-cultural heritage of the Mediterranean region, an area recognized as a global biodiversity hotspot. In the midst of the global biodiversity and climate crisis, immediate actions are proposed for the protection and conservation management of TAFSs, within a new EU policy framework. Having the TAFSs of Greece in the spotlight of this analysis, a four-step approach was used in order to review the value of agroforestry in terms of (a) biodiversity (birds, mammals, invertebrates and soil biota), (b) agroforestry landscapes, such as traditional olive groves on terraces and valonia silvopastoral systems, (c) ecosystem services, especially concerning cultural values, and (d) the modern threats to traditional agroforestry. Through this research, problems are highlighted and European policy priorities are defined. Our conclusion is that there is an immediate need to revise the European Union rural, forestry, and environmental policies in the Mediterranean region, following the provisions of the new EU Nature Restoration Law, in order to revive agroforestry landscapes and make them productive and sustainable again for the benefit of rural economies, local communities, and biodiversity, especially in marginal Mediterranean mountainous and island areas, where depopulation and susceptibility to wildfires are major threats.

Ecological implications of deep pruning: a case report on Persian squirrel nesting in a centennial olive grove on the island of Lesvos, Greece

In recent years, traditional olive groves have undergone a shift towards modern farming practices, raising concerns about their potential impact on local fauna. Despite the documented effects of various agricultural practices on wildlife, there is a notable gap in understanding the implications of pruning practices in traditional olive groves. This study presents a unique observation, the first documented adverse effect of pruning on an olive tree within a traditional grove in Lesvos, Greece, inhabited by Persian squirrels (Sciurus anomalus). Beyond immediate impacts, we conducted comprehensive measurements of both the pruned olive tree and the squirrel’s nest (den), along with an assessment of the entire grove. The findings highlight the need for ecologically informed olive grove management to sustain biodiversity in these historically significant environments.

Open-Format Prescription Maps for Variable Rate Spraying in Orchard Farming

Highlights Straightforward procedure to code prescription maps independent of manufacturers. Methodology suitable for orchard crops and vineyards including pressures up to 10 bar and flowrates up to 100 L/min. Algorithm validated for both trellis-based continuous rows and traditional orchard rows of discrete trees. Method scalable to other agricultural operations, such as fertilizing or data registration for auditing purposes. Abstract. The implementation of crop protection solutions contributing to significant reductions in the use and risk of chemical pesticides has motivated the interest of site-specific systems, such as variable rate technologies based on user-set prescriptions. However, the practical implementation of variable rates has been dissuasive for many growers who are not familiar with digital solutions, as proprietary firmware is often difficult to grasp. This paper presents a method for formatting prescription maps that is independent of manufacturers, can be easily and freely implemented by industry and can be adopted by growers not familiar with advanced software tools. The methodology was successfully demonstrated for perennial specialty crops, in particular for trellised vineyards in vertical shoot position and for traditional olive groves. Results showed that the variations within user prescription maps were translated to the fields, but flow errors appeared due to the challenge of measuring flow and pressure in the highly pulsating actuation of pulse-width-modulated (PWM) valves. Such errors diminished with the use of low-volume rates and the optimal selection of the nozzles when adjusted to the real pressure measured in the field. The use cases validated in the field showed the consistency of the method for highly populated prescription maps of 1,221 points/ha accessible to advanced farmers, as well as for modest maps of 80 points/ha within reach of the majority of growers. Keywords: Automated map building, Local tangent plane coordinates, Orchard crop operations, Precision farming, Prescription maps, User-centered approach, Variable rate spraying.

Linking Thermal Indices, Productivity, Phenotypic Traits, and Stressors for Assessing the Health of Centennial Traditional Olive Trees

Centennial olive trees, integral components of traditional Mediterranean agroecosystems, hold immense value as repositories of biodiversity and cultural heritage due to their physiological attributes and life history, making them crucial for the conservation of High Nature Value ancient olive orchards. However, they are increasingly confronted with physiological challenges exacerbated by various biotic and abiotic stressors jeopardizing their health and productivity, underscoring the urgency for ongoing monitoring and conservation measures to secure their long-term existence. To monitor these challenges, in recent years, the adoption of non-invasive techniques like infrared thermography (IRT) has become prevalent. In this study, we aimed to comprehensively assess the health state of traditional centennial olive trees, with a particular focus on their productivity. To achieve this, we monitored 44 centennial olive trees from a traditional olive grove on the island of Naxos, Greece, a representative location for Mediterranean olive groves, during the period from 2017 to 2020. We established connections between a set of trunk and canopy thermal and humidity indices, phenotypic traits, and the two most prevalent stressors affecting olive trees not only within the context of the island but also more broadly in similar Mediterranean environments worldwide: the olive leaf spot disease (OLS) and crop water stress, assessed through the crop water stress index (CWSI). To evaluate their interrelationships, we initially assessed intraspecific thermal and humidity pattern variations, and we developed linear and logistic regression models to gain insights into the factors influencing olive tree productivity, water stress, and the OLS presence. Results indicated that combining thermal and humidity indices can substantially explain olive tree productivity, water stress, and OLS, providing a valuable tool for assessing and monitoring the health and overall state of centennial olive trees, while offering a comprehensive approach to understanding the complex interactions shaping traditional olive grove dynamics. By identifying key indicators such as tree thermal patterns and water stress levels, olive growers and conservationists can make informed decisions to enhance the vitality and longevity of these culturally and ecologically significant trees.

Traditional ploughing is critical to the conservation of threatened plants in Mediterranean olive groves

Arable plant diversity has been dramatically declining due to agriculture intensification, with several arable species currently included in national Red Lists. This is particularly relevant in the case of plant communities of the traditional Mediterranean agricultural systems. Despite the current knowledge about the factors affecting this diversity, it is not clear how these communities, which have likely evolved under the pressure of ploughing for millennia, depend on this regular soil disturbance. This is an important issue nowadays, because current management practices focused on the conservation of the ground vegetation cover, to protect soil and other biological groups, often exclude ploughing. In this paper, we test the hypothesis that traditional ploughing is favourable to more specialist arable plants, predictably more dependent on the regular soil disturbance. We address this issue in a Mediterranean agricultural system, the traditional olive groves of Southern Portugal, which is characterized by the annual ploughing of soil. A total of 90 plots containing 1350 sampling quadrats were sampled, and all plant species identified. We categorized plants in four target groups of conservation interest, and then used a joint species distribution model to model their occurrence in relation to three management practices: ploughing, cultivation and low-intensity grazing, using abandoned olive groves as reference level. Results suggest that ploughing is a key factor for the maintenance of arable plant diversity. Ploughing had a positive effect on the occurrence of rare arable plants, archaeophytes and on several Red listed species. In order to conserve these high value plant communities and endangered plant species, we recommend incentivizing ploughing using reduced tillage techniques (e.g. chisel ploughing) on these traditional Mediterranean agricultural systems.

Olive Grove Landscapes in Andalusia: In Search of Synergies Between Agrarian Cultural Heritage and Rural Development

Summary This paper analyses the strategy developed thus far to have Andalusian olive-growing landscapes included as a Cultural Landscape on the World Heritage List (UNESCO). The research method used is descriptive, reflexive and prospective, and seeks to achieve a systematic and holistic overview of a complex reality. In addition to the corresponding bibliographical review, the research has been nourished by qualitative information from land surveys (field visits) and interviews with experts consulted during the preparation of the two technical dossiers of the candidacy produced so far. The results include the rationale for Outstanding Universal Value and the basis of the protection and management plan for the property. Subsequently, the paper discusses the possibilities for rural development that can be derived from this initiative through the virtuous interactions between the property, the region and the food (olive oil) obtained from traditional olive groves.

Soil Erosion in Extensive versus Intensive Land Uses in Areas Sensitive to Desertification: A Case Study in Beira Baixa, Portugal

The occurrence of long periods of drought followed by extreme episodes of rainfall and ineffective soil conservation practices are the main causes of soil erosion in the Mediterranean region. The objective of this paper is to assess and compare the hydrological and erosional responses related to land use changes in agricultural landscapes that are sensitive to erosion and that are a result of the significant replacement of traditional land uses. Such changes are characterized by the replacement of extensive olive groves associated with pastureland by intensive almond production, where deep plowing and heavy machinery are required. In each sampling site, runoff initiation, runoff coefficient, and soil loss were evaluated under simulated rainfall (55 mm h−1), at plot scale (0.25 m2), at the end of the hot and dry summer period. Slope gradient, soil texture, bulk density, soil organic matter content, soil water content, and plant cover were also determined. The results showed the impact of recently planted intensive almond orchards (IAOs) on accelerating soil erosion risk compared with the extensive traditional olive groves (EOGs), although runoff initiation and discharge are very similar between the studied land uses. The mean values recorded for soil loss and sediment concentration were 118 g m−2 h−1 and 12 g m−2 h−1 and 3.1 g L−1 and 0.7 g L−1, respectively, for IAOs and EOGs. Our results also demonstrated that maintaining a vegetation cover is a determining factor for the prevention and control of soil erosion, especially in IAOs, where retaining high percentages of natural plant-residue mulch layers (>70%) reduced soil loss by about 70% in this study.

Assessment of the Spatial Variability and Uncertainty of Shreddable Pruning Biomass in an Olive Grove Based on Canopy Volume and Tree Projected Area

Olive pruning residues are a by-product that can be applied to soil or used for energy production in a circular economy model. Its benefits depend on the amount of pruning, which varies greatly within farms. This study aimed to investigate the spatial variability of shreddable olive pruning in a traditional olive grove in Córdoba (Spain) with an area of 15 ha and trees distanced 12.5 m from each other. To model the spatial variability of shreddable olive pruning, geostatistical methods of stochastic simulation were applied to three correlated variables measured on sampled trees: the crown projected area (n = 928 trees), the crown volume (n = 167) and the amount of shreddable pruning (n = 59). Pearson’s correlation between pairs of variables varied from 0.71 to 0.76. The amount of pruning showed great variability, ranging from 7.6 to 76 kg tree−1, with a mean value of 37 kg tree−1. Using exponential and spherical variogram models, the spatial continuity of the variables under study was established. Shreddable dry pruning weight values showed spatial autocorrelation up to 180 m. The spatial uncertainty of the estimation was obtained using sequential simulation algorithms. Stochastic simulation algorithms provided 150 possible images of the amount of shreddable pruning on the farm, using tree projected area and crown volume as secondary information. The interquartile range and 90% prediction interval were used as indicators of the uncertainty around the mean value. Uncertainty validation was performed using accuracy plots and the associated G-statistic. Results indicate with high confidence (i.e., low uncertainty) that shreddable dry pruning weight in the mid-western area of the farm will be much lower than the rest of the farm. In the same way, results show with high confidence that dry pruning weight will be much higher in a small area in the middle east of the farm. The values of the G-statistic ranged between 0.89 and 0.90 in the tests performed. The joint use of crown volume and projected areas is valuable in estimating the spatial variability of the amount of pruning. The study shows that the use of prediction intervals enables the evaluation of farm areas and informed management decisions with a low level of risk. The methodology proposed in this work can be extrapolated to other 3D crops without requiring modifications. On a larger scale, it can be useful for predicting optimal locations for biomass plants, areas with high potential as carbon sinks or areas requiring special soil protection measures.

Lack of refuge as a bottleneck for reptiles in intensive woody crops

Abstract The lack of refuge has been suggested as one of the main factors affecting reptiles in intensive crops, but this theory has not been explored to any great extent. The aim of this work is to compare the reptile abundance and species richness between traditional and intensive vineyards and olive groves, and to test the acceptance of artificial shelter due to its scarcity in the new intensive woody crop. A total of 288 transects were carried out (144 in olive groves and 144 in vineyards) in six different types of plots: traditional olive groves, traditional vineyards, intensive olive groves with and without artificial refuge, and trellis vineyards with and without artificial refuge. The results showed a greater species richness and abundance of reptiles in the traditional plots than in the intensive plots (independently of the experimental refuges added). An important number of animals were observed using the artificial refuges in olive groves. Furthermore, most of the individuals were located on or escaped to old trees in traditional systems, including an important proportion of reptiles hidden in olive trunk cavities, whereas more individuals were observed on the ground in intensive systems. Our finding suggests the importance for reptile communities of the traditional agricultural systems due to the high availability of the refuge provided by old olive tree trunks and free-standing gobelet vineyards. Our results show that providing refuge may mitigate the negative effects of woody crops intensification on reptile communities.

Entrapped in Olive-Harvesting Nets: A Case of a Grass Snake Natrix natrix from an Olive-Growing Greek Aegean Island

Despite a recent shift towards sustainable practices to support the conservation of traditional olive groves, little is known about their potential threats to herpetofauna species. On the island of Lesvos, one of the main olive-growing islands in the Mediterranean, olive cultivation often prioritizes the expeditious harvesting of olives with minimal or no supplementary intervention, resulting in their generally suboptimal management, a component of which also pertains to the olive nets that, in many cases, remain dispersed and unfurled throughout the groves. This particular practice affects the species living in the olive groves, making them more prone to risks related to their accidental trapping. In this study, we report the first case of a Grass snake being inadvertently trapped in an olive net laid out on an olive grove. The position of the snake under the net, within a folded tipping, made it difficult for it to escape, and it became increasingly entangled. Based on this incident, it is plausible to assume that similar cases may occur in areas where nets are used in olive groves, both in Greece and other olive-growing countries. Further systematic research is necessary to determine the extent of this issue.

Mite community assemblage in Italian traditional and in high-density olive groves

Notwithstanding a still widespread and considerable weight of traditional olive groves throughout Italy, there is large interest in investing in new plantations, different both for cultivars and agronomic approaches, and to renew at least partially the olive-oil heritage. Furthermore, Italy is one of the main importing countries in the world of oil and table olives. To match the internal demand and boost olive-oil production, the National Olive Plan suggests adopting modern high-density plantations like other EU Countries (e.g., Spain). Traditional groves are partly replaced by high-density olive crops, which are more profitable due to substantially lower operating costs. Furthermore, the introduction of new olive crops may induce changes in agricultural landscape/agroecosystem (e.g., plain areas vs terraced structures), and may lead to undesirable effects on the environment and pest control. The surveys on the presence and abundance of the main animal groups in traditional and high-density olive crops can be informative, mainly referring to the different ecological/functional roles they can assume (phytophagous, predatory, and vectoring role of pathogens). Mite communities are susceptible to different types of plantation density and eventual environmental effects. Concerning olives, not so many contributions approached screening on the acarofauna, and previous screenings were mainly focused on soil. The characterization of the acarofauna resident on epigeic part of olive groves may be indicative about the status of the agroecosystem and effect of plantation densities.

Detection of Planting Systems in Olive Groves Based on Open-Source, High-Resolution Images and Convolutional Neural Networks

This paper aims to evaluate whether an automatic analysis with deep learning convolutional neural networks techniques offer the ability to efficiently identify olive groves with different intensification patterns by using very high-resolution aerial orthophotographs. First, a sub-image crop classification was carried out. To standardize the size and increase the number of samples of the data training (DT), the crop images were divided into mini-crops (sub-images) using segmentation techniques, which used a different threshold and stride size to consider the mini-crop as suitable for the analysis. The four scenarios evaluated discriminated the sub-images efficiently (accuracies higher than 0.8), obtaining the largest sub-images (H = 120, W = 120) for the highest average accuracy (0.957). The super-intensive olive plantings were the easiest to classify for most of the sub-image sizes. Nevertheless, although traditional olive groves were discriminated accurately, too, the most difficult task was to distinguish between the intensive plantings and the traditional ones. A second phase of the proposed system was to predict the crop at farm-level based on the most frequent class detected in the sub-images of each crop. The results obtained at farm level were slightly lower than at the sub-images level, reaching the highest accuracy (0.826) with an intermediate size image (H = 80, W = 80). Thus, the convolutional neural networks proposed made it possible to automate the classification and discriminate accurately among traditional, intensive, and super-intensive planting systems.

Canopy recovery in traditional olive groves: preliminary results

Canopy recovery in traditional olive groves: preliminary results

Agricultural Landscapes as a Basis for Promoting Agritourism in Cross-Border Iberian Regions

Areas with low levels of transformation are alternative destinations for tourists who prefer to visit nonmassified places and have singular experiences. The benefits of these microdestinations are their local populations, traditional products, landscapes, and heritage, which, in turn, allow the cultural and gastronomic roots to be witnessed. Based on this assumption, the present research investigated landscape preferences in the Tejo/Tajo International Transboundary Biosphere Reserve (Portugal/Spain), where Dehesa/Montado and traditional olive groves play important economic and sociocultural roles. This investigation sought to compare the opinions of those who live there with those who visit the territory in terms of landscape and agritourism experience preferences. To this, 439 interviews were conducted, and the results were extracted through descriptive analysis techniques and parametric and nonparametric tests to understand the different opinions. The main results were that agricultural landscapes are among the most preferred, and visitors tend to give the landscape higher scores, while the local population has some ignorance of its potential. The potential of agritourism was revealed through the motivation expressed by the demand to participate in gastronomic experiences and have contact with local products, followed by participation in activities that allow people to enjoy the agricultural landscape and rural traditions. The results revealed that the agritourism concept is often confused with rural tourism and nature tourism. Thus, it is necessary to develop a strategy to support the tourism supply according to the concept of authentic agritourism. In this way, agricultural activity has an important role in driving sustainable tourism dynamics in cross-border regions and boosting new products based on the culture, nature, and biodiversity characteristics of a protected area.

Analysis of Oleotourism and Museology: Bibliometric Analysis and Systematic Literature Review

Traditional Olive Grove represents about 80% of the awards in the National Olive Oil Competition of Portugal, substantiating the importance and relevance of the sector. The term "oleotourism" is considered as a movement that increasingly aims to know all the features, qualities, and differences in olive oil production. As a dynamic movement, this term uses museology to present and promote its products to the public and tourism. From museology articles, it was understood that the museums should not be limited to the institutionally conceived idea, instead of that, it should be understood as a global science of a distinct, which encompasses the universe and society. Subsequently, the relevance of conducting qualitative research arises, studying the literature on oleotourism associated with museology and analysing their contributions and effects on tourism. After reviewing the existing databases, the SCOPUS database was selected to collect and analyse the bibliographic material. Hence, as the purpose, this study aimed to highlight the scientific publications with the most significant impact of the terms "oleotourism" and "museology", understanding their research trends. In the systematisation process, we considered the final 100 articles with the most citations published in journals between 2005 and 2021. The articles analysed were reviewed using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses for the systematic literature review. For the bibliometric analysis, the Bibliometrix R program was used. As a result, from the bibliometric analysis, it was found that, as research trends, the keywords "olive oil tourism" and "museums" were highlighted, with Italy, Spain and the United Kingdom as the countries with the most citations. In addition, the journals "Sustainability", "Museum Anthropology", and "Museum Management and Curation" in the publications on these themes are highlighted. In comparison, through the systematic literature review, it was understood that the research trends focused on: the conceptualisation of oleotourism; the influence of museology on tourism; and the importance of museum education. Despite the importance of this research in helping future studies, there are some limitations on their analysis, which will be recommended to use specific databases for the themes and increase the number of articles considered.

Soil management and compost amendment are the main drivers of carbon sequestration in rainfed olive trees agroecosystems: An evaluation of chemical and biological markers

Traditional olive groves are considered at high risk of erosion and desertification due to low organic matter inputs and scarce vegetation cover coupled to highly intensity tillage, leading to a further decrease in soil organic carbon contents. In a context of climate change, carbon sequestration through waste management in the framework of a circular economy becomes of primary importance for rainfed Mediterranean agricultural soils. To unveil the mechanisms of carbon sequestration in those agroecosystems, we evaluated the effect of the application of two composts (olive waste “alperujo” and biosolid) at two different doses coupled to the sustainable soil management allowing spontaneous vegetation growing on the soil surface.With this aim, solid state nuclear magnetic resonance was used to trace the evolution of the chemical composition of compost-derived and soil-derived organic matter. Successively, the activity of soil microbial community after the compost addition was monitored by measuring two enzymatic activities (β-glucosidase and dehydrogenase) and soil CO2 respiration. Lastly, the adaptation of microbial communities was quantified using the genes encoding soil enzymes associated with C cycling -glucosidase and laccase-like multicopper oxidases. The results of this study show that biosolid compost has a higher potential for C storage at mid-term (24 to 30 months after first application) than alperujo compost, yielding up to 50% net C sequestration in the topsoil in addition to the compost-derived C applied. We attribute these results to biosolid compost chemical composition, closer to that of the native organic matter, which led to a less abrupt adaptation of soil microbial functioning (lower flushes of water soluble C, lower number of copies of genes encoding enzymatic activities) to the new C source, if compared to alperujo compost. The results encourage the reduction of soil perturbation and the use of organic amendments instead of mineral fertilizers to increase carbon storage and improve sustainability of olive groves in the Mediterranean agroecosystems.

Olive Oil Sensory Analysis as a Tool to Preserve and Valorize the Heritage of Centenarian Olive Trees.

In inland areas of Portugal and some regions of the Mediterranean basin, olive production is based on traditional olive groves, with low intensification, local cultivars, aged plants, and centenarian trees. These plants play a key role in the ecosystem, contributing to carbon sequestration and possessing a high genetic diversity, particularly important for selecting cultivars more resistant to climatic changes. Appreciation of the value of this genetic diversity implies genetic, morphological, and physicochemical characterization of centenarian trees, which is expensive and time-consuming. Sensory evaluation is also of utmost importance. Thus, in this study, centenarian olive trees were selected in the Côa Valley region, a UNESCO World Heritage site. The descriptive sensory profile of their extracted olive oils was established and used to cluster the oils, using hierarchical clustering analysis, and consequently the olive trees, into five groups with similar intensities of perceived olfactory–gustatory attributes. Each cluster revealed olive oils with unique sensory patterns, presumably due to similarities of the olive trees, confirming the potential of the proposed screening approach. The identification of sensorially homogeneous oil-tree groups would reduce the number of specimens needed for subsequent morphological, genetic, and chemical characterization, allowing a cost-effective and robust future evaluation procedure.

Landscape Characteristics Affecting Small Mammal Occurrence in Heterogeneous Olive Grove Agro-Ecosystems

Understanding how small mammals (SM) are associated with environmental characteristics in olive groves is important to identify potential threats to agriculture and assess the overall conservation value and functioning of agro-ecosystems. Here, we provide first insights on this topic applied to traditional olive groves in northeast (NE) Portugal by assessing the landscape attributes that determine SM occurrence, focusing on one species of conservation concern (Microtus cabrerae Thomas 1906) and one species often perceived as a potential pest of olives (Microtus lusitanicus Gerbe 1879). Based on SM genetic non-invasive sampling in 51 olive groves and surrounding habitats, we identified seven rodent species and one insectivore. Occupancy modelling indicated that SM were generally less detected within olive groves than in surrounding habitats. The vulnerable M. cabrerae reached a mean occupancy (95% CI) of 0.77 (0.61–0.87), while M. lusitanicus stood at 0.37 (0.24–0.52). M. cabrerae was more likely to occur in land mosaics with high density of agricultural field edges, while M. lusitanicus was more associated with high density of pastureland patches. Overall, our study suggests that the complex structure and spatial heterogeneity of traditionally managed olive grove agro-ecosystems may favor the occurrence of species-rich SM communities, possibly including well-established populations of species of conservation importance, while keeping potential pest species at relatively low occupancy rates.

Estimating Productivity, Detecting Biotic Disturbances, and Assessing the Health State of Traditional Olive Groves, Using Nondestructive Phenotypic Techniques

Conservation of traditional olive groves through effective monitoring of their health state is crucial both at a tree and at a population level. In this study, we introduce a comprehensive methodological framework for estimating the traditional olive grove health state, by considering the fundamental phenotypic, spectral, and thermal traits of the olive trees. We obtained phenotypic information from olive trees on the Greek island of Lesvos by combining this with in situ measurement of spectral reflectance and thermal indices to investigate the effect of the olive tree traits on productivity, the presence of the olive leaf spot disease (OLS), and olive tree classification based on their health state. In this context, we identified a suite of important features, derived from linear and logistic regression models, which can explain productivity and accurately evaluate infected and noninfected trees. The results indicated that either specific traits or combinations of them are statistically significant predictors of productivity, while the occurrence of OLS symptoms can be identified by both the olives’ vitality traits and by the thermal variables. Finally, the classification of olive trees into different health states possibly offers significant information to explain traditional olive grove dynamics for their sustainable management.

Transpiration and Water Use of an Irrigated Traditional Olive Grove with Sap-Flow Observations and the FAO56 Dual Crop Coefficient Approach

The SIMDualKc model was applied to evaluate the crop water use and the crop coefficient (Kc) of an irrigated olive grove (Olea europaea L.) located in Sicily, Italy, using experimental data collected from two crop seasons. The model applies the FAO56 dual Kc approach to compute the actual crop evapotranspiration (ETc act) and its components, i.e., the actual tree transpiration (Tc act), obtained through the basal crop coefficient (Kcb), and soil evaporation according to an evaporation coefficient (Ke). Model calibration was performed by minimizing the difference between the predicted Tc act and the observed daily tree transpiration measured with sap flow instrumentation (TSF field) acquired in 2009. The validation was performed using the independent data set of sap flow measurements from 2011. The calibrated Kcb was equal to 0.30 for the initial and non-growing season stages, 0.42 for the mid-season, and 0.37 for the end season. For both seasons, the goodness-of-fit indicators relative to comparing TSF field with the simulated Tc act resulted in root mean square errors (RMSE) lower than 0.27 mm d−1 and a slope of the linear regression close to 1.0 (0.94 ≤ b0 ≤ 1.00). The olive grove water balance simulated with SIMDualKc produced a ratio between soil evaporation (Es) and ETc act that averaged 39%. The ratio between actual (ETc act) and potential crop evapotranspiration (ETc) varied from 84% to about 99% in the mid-season, indicating that the values of ETc act are close to ETc, i.e., the adopted deficit irrigation led to limited water stress. The results confirm the suitability of the SIMDualKc model to apply the FAO56 dual Kc approach to tree crops, thus assessing the water use of olives and supporting the development of appropriate irrigation management tools that are usable by farmers. A different way to estimate Kcb is based on the approach suggested in 2009 by Allen and Pereira (A&P), which involves the measured fraction of ground covered (shaded) by the crop and the height of the trees. Its application to the studied grove produced the mid-season Kcb values ranging from 0.40–0.45 and end-season Kcb values ranging from 0.35–0.40. The comparison between the A&P-computed Tc act A&P and TSF field shows RMSE values ranging from 0.27 to 0.43 mm d−1, which demonstrates the adequacy of the latter approach for parameterizing water balance models and for irrigation scheduling decision making.