Cultivar ideotype for intensive olive orchards: plant vigor, biomass partitioning, tree architecture and fruiting characteristics

In order to achieve higher and earlier yield, modern olive orchards are increasingly intensified, with tree densities up to > 1500 trees hectare-1. With increasing tree densities, individual-tree canopy volume must be proportionally reduced. Not all cultivars are adaptable to high and very high orchard densities, because of excessive vigor and/or insufficient bearing when the canopy is pruned to a small volume. However, what makes an olive cultivar suitable for intensive and super intensive orchards is not clear. Recently, few studies have addressed this topic, suggesting that tree architecture and early bearing are essential traits. Yet, what architectural and productive features are important, how they work and whether they are interrelated remains elusive. This review summarizes and interprets the literature on olive, as well as the more abundant literature available for other fruit species, aiming to provide a comprehensive knowledge framework for understanding how tree architectural characteristics, plant vigor, and fruiting vary across olive genotypes, and how they are interconnected. It is concluded that, among the architectural characteristics, greater branching and smaller diameters of woody structures are particularly important features for cultivar suitability to intensive and super intensive olive orchards. Greater branching allows to produce more fruiting sites in the small volume of canopy allowed in these systems. It also reduces investments in woody structures, liberating resources for fruiting. Additional resources are liberated with smaller structure diameters. Greater branching also increases resources by increasing biomass partitioning into leaves (i.e. the photosynthetic organs), relative to wood. Since yield is affected by the competition for resources with vegetative growth, reducing resource investments in woody structures and/or increasing resource directly, increases yield. Yield, in turn, depresses vegetative growth, reducing vigor and the need for pruning. High yields also produce short shoots which have relatively greater investments in leaf mass and area, and lower in the woody stem, making them more suitable than long shoots to support concurrent fruit growth. This single framework of interpretation of how the different architectural and fruiting characteristics work and interact with one-another, will provide guidance for cultivar selection and breeding for intensive and super intensive olive orchards

An Alternative Tool for Intra-Row Weed Control in a High-Density Olive Orchard

none6openAssirelli, Alberto; Ciaccia, Corrado; Giorgi, Veronica; Zucchini, Matteo; Neri, Davide; Lodolini, Enrico MariaAssirelli, Alberto; Ciaccia, Corrado; Giorgi, Veronica; Zucchini, Matteo; Neri, Davide; Lodolini, Enrico Mari

Acclimation ex vitro: How to improve the root system

Acclimation ex vitro is considered one of the most critical stages of the whole micro-propagation cycle. The root system is still weak and root growth and absorption need to be improved to compensate the increasing leaf transpiration and need of nutrients. The experiments presented in this study aimed to improve the aerial and root growth by using different substrates (type and mode of filling of the pots) in combination with specific fertilizers and replacing part of the root absorption with nutrient application to the leaves. The supply of mineral elements and organic compounds to the leaves in synergy with the available reserves in the seedlings can avoid the increasing of the cost of the absorption process for the plantlet. Results confirm the importance of the substrate to affect root growth and establishment. The quality of the growth of root and foliar P, K, Ca, Mg, and humic acids application positively influenced the growth and the plant settlement. Results showed that foliar applications in fertilized growing media are able to enhance vegetative growth, dry matter accumulation and basal steam diameter in all the tested clones. When nonfertilized growing media are used, foliar application is less effective in controlling vegetative growth to obtain the required height and basal stem diameter. This study suggests that is advisable to have a micro-porous substrate and apply moderate fertilizations through the substrate. The supply of the nutrients to the leaves resulted in bigger, but well hardened plants. It is possible to argue that changing concentrations and ratio among the different elements according to the acclimation cycle stage would balance vegetative growth and reduce hidden stresses

La gestione del suolo

Soil management is one of the key practices that influence the vegetative and reproductive activity of the olive tree. Tillage, green cover (permanent or temporary), herbicide application and mulching are all used in olive growing. Tillage is still the preferred method worldwide, but the use of properly managed green covers is strongly suggested for greater sustainability of the olive orchard. Tillage is advantageous for weed removal, easy application of fertilizers, and storage of precipitation water, and it favors mineralization of organic matter. However, it may cause erosion in sloping areas with considerable losses of soil, organic matter and nutrients. Green covers reduce erosion and ease trafficking of machinery when the soil is moist, as often happens at harvesting time. Yet, permanent green covers increase water consumption which may be detrimental in arid climates. Herbicide application and mulching are not as common as tillage or green covers in Italian olive orchards. Herbicides eliminate weeds, but have a greater environmental impact than other methods of soil management. To reduce chemical inputs in the orchard, herbicides are often used only along the tree row, combined with intercropping or tillage in the inter-row. Mulching with polyethylene sheets is mainly limited by the cost and difficulty of disposing of the plastic sheets, whereas mulching with organic material is limited to family-run olive orchards due to shortage of mulching material. The new frontier of using living mulch or other plants in the olive orchard is discussed

Effects of olive shoot residues on shoot and root growth of potted olive plantlets

tDecomposition of olive shoot residue (OSR) from leaf shedding and pruning may provide nutrient toolive orchards, although beyond a phytotoxic threshold it can also hamper plant growth. We studiedOSR decomposition effects on plant growth, biomass partitioning and soil fertility. Four levels of OSR (0%,3%, 10% and 30% [v/v]) were mixed into the substrate and placed close to the roots compared on twoolive potted cultivars over 240 days using a destructive sampling approach. Organic matter, polyphe-nol and nitrogen contents in the substrate, fine root respiration and electrolyte leakage, leaf pigmentcontent, chlorophyll a fluorescence, biomass partitioning, fine root nutritional status were determined.OSR increased the content of organic matter, polyphenols and nitrogen in the soil. In the first 150 days,OSR beyond 3% induced autotoxic effects, and altered fine root respiration, and electrolyte leakage andbiomass allocation. After 240 days, OSR induced a stimulatory effect on fine roots and shoot growth andincreased shoot and fine root nitrogen content. Application OSR did not significantly altered leaf pig-ment content and chlorophyll a fluorescence. As a conclusion, above the threshold of 3%, olive cannotprevent autotoxicity during the early decomposition of OSR, but later soil fertility and plant growth canbe increased

Physical, Chemical and Biological Properties of some Alternative Growing Substrates.

Peat represented the predominant constituent of growing media for soilless production in the last decades. However, due to the high cost of extraction and future availability and sustainability, a worldwide search for alternative substrates has been developed, focusing on secondary processing compounds or recycling wastes. In order to evaluate the suitability of new materials, organic by-products, namely hemp fiber (2 particle sizes) and grape marc were studied and compared with peat and some rising substitutes: Coir (3% fiber) and green compost. Methodology: Some of the main physical (particle size distribution, bulk density, water holding capacity and air capacity), chemical (pH, electrical conductivity, ash, carbon, hydrogen, nitrogen and heavy metals content) and biological properties (phytotoxicity) were analyzed. Results: All materials showed water holding capacity >40% (threshold considered sufficient on the base of peat-related classification), except for coir and hemp with large particle size and marc that registered a poor water-holding capacity (<40% retained water). The pH of the base materials was different with values ranging between 6.21 and 9.05. Compost and marc showed high values of electrical conductivity and copper content (and heavy metals for green compost) and a possible negative influence on germination of cress as resulting from the bioassay. Conclusion: Physical, chemical and biological properties of the materials suggested that coir has the potential to partially or totally replace peat, whereas marc and compost require to be mixed with other materials or properly select the source-of-origin materials before processing

Architectural characteristics of six olive cultivars with respect to their suitability for high density orchards

In a high density (1,250 trees ha-1) olive orchard in central Italy, the architectural characteristics of ‘Arbequina’, ‘Arbosana’, ‘Koroneiki’, ‘FS17’, ‘Don Carlo’ and ‘Giulia’ cultivars was studied. Tree height, canopy dimensions, trunk diameter at 0.20, 0.75, 1.5, 2.0 m from the ground, branch intersection height along the trunk, diameter and length of the primary branches were measured in 2010, when trees were 2-year-old. On sampled branches at different height, all the productive and vegetative shoots were spatially described. Tree height, trunk diameter and canopy volume were not significantly different among cultivars, while the number of primary branches was lower in ‘FS17’ compared to ‘Arbequina’, ‘Arbosana’ and ‘Koroneiki’. The studied cultivars had different branching patterns along the trunk: a low density between 1 and 1.5 m trunk height in ‘FS17’ and a high between 1.5 and 2.0 m in ‘Arbequina’. Moreover, the length/diameter ratio of the primary branches was low and high in ‘Arbosana’ and ‘Giulia’ and in ‘Arbequina’, respectively. ‘Arbequina’ also showed a uniform shoot density along the main axis of the primary branch, whereas an alternate shoot density with the presence of empty portions was observed in the other cultivars. A higher shoot density in the medium-proximal portion of the branch was seen for ‘Arbosana’ and ‘FS17’. Results presented in this study supply helpful information about the different canopy and branch architectural characteristics of the six studied olive cultivars with respect to their suitability to high density plantations

Preliminary Results about the Influence of Pruning Time and Intensity on the Vegetative Growth and Fruit Yield of a Semi-intensive Olive Orchard

The effect of extending the pruning time and reducing the pruning intensity was investigated on vegetative response and production of three Italian olive cultivars (‘Raggia’, ‘Maurino’ and ‘Leccino’) in central Italy. From 2009 to 2011, pruning was performed on 5-years-old olive trees in early spring (after bud break) at two intensity levels (minimal and heavy) and in late spring (after full bloom) at a heavy intensity. A control set of plants was left unpruned during the experiment. Results showed that the absence of pruning minimized water sprouts growth and initially generated the highest yield. The productive advantage offered by not pruning decreased at the third year. After 3 years of no pruning, the plants showed an excessive height, shading of the central portion of the canopy, and negligible vegetative growth, inducing an early senescence of the productive branches and necessitating the removal of a massive amount of dry material by applying a severe pruning operation (rejuvenation) at the end of the trial. The early spring minimal pruning technique led to the lowest amount of pruning material and provided a consistent increase in plant production compared to heavy pruning. Late spring pruning did not provide competitive advantages in terms of vegetative re-sprouting control nor yield compared to early pruning. This preliminary study suggests early spring minimal pruning in central Italy as the best practice to increase stability in yield and to control the vegetative growth of olive trees in semi-intensive orchards

Reproductive patterns of 1-year-old mixed shoots in different olive cultivars in Central Italy.

The increase of plant density in new olive orchard systems requires a deeper investigation about plant architecture to understand growth, branching pattern and yield and to select most suitable cultivars. The spatial arrangement of vegetative and reproductive structures helps to explain the fruiting attitude of the plant at different levels: the whole tree, the productive branch and the fruiting shoot. The objective of the present study was to investigate the reproductive attitude of 1-year-old mixed shoots in six olive cultivars grown in central Italy in order to determine inflorescence and fruit distribution and identify correlations between vegetative-reproductive variables. Results showed a differing inflorescence and fruit distribution along the shoot axis: a higher number in the median-distal portion for the cultivars ‘Arbequina’, ‘Don Carlo’ and ‘Giulia’, in the median-basal portion for ‘FS17’ and more homogeneous for ‘Arbosana’ and ‘Koroneiki’. A higher fruit number with increasing length of 1-yearold mixed shoot was registered, but with a shallow slope relationship compared to the number of flowers per shoot. After fruit set, the crop load remained constant until harvest. Cultivars showed a different vegetative-reproductive pattern in the climatic conditions of central Italy with differences between all cultivars. This study contributes to understand the reproductive pattern of 1-year-old mixed shoot in olive, suggesting a different suitability of the cultivars to different planting density systems