High-density Orchards Research Articles

Rootstock breeding in Prunus species: Ongoing efforts and new challenges

The current global agricultural challenges imply the need to generate new technologies and farming systems. In this context, rootstocks are an essential component in modern agriculture. Most currently used are those clonally propagated and there are several ongoing efforts to develop this type of plant material. Despite this tendency, lesser number of rootstock breeding programs exists in comparison to the large number of breeding programs for scion cultivars. In the case of rootstocks, traits evaluated in new selection lines are quite different: From the agronomic standpoint vigor is a key issue in order to establish high-density orchards. Other important agronomic traits include compatibility with a wide spectrum of cultivars from different species, good tolerance to root hypoxia, water use efficiency, aptitude to extract or exclude certain soil nutrients, and tolerance to soil or water salinity. Biotic stresses are also important: Resistance/tolerance to pests and diseases, such as nematodes, soil-borne fungi, crown gall, bacterial canker, and several virus, viroids, and phytoplasms. In this sense, the creation of new rootstocks at Centro de Estudios Avanzados en Fruticultura (CEAF) offers an alternative to stone fruit crop, particularly in Chile, where just a few alternatives are commercially available, and there are site-specific problems. The implementation of molecular markers in order to give support to the phenotypic evaluation of plant breeding has great potential assisting the selection of new genotypes of rootstocks. Marker-Assisted Selection (MAS) can shorten the time required to obtain new cultivars and can make the process more cost-effective than selection based exclusively on phenotype, but more basic research is needed to well understood the molecular and physiological mechanisms behind the studied trait.

Olive genotypes cultivated in an adult high-density orchard respond differently to canopy restraining by mechanical and manual pruning

Three-year observations about the canopy restraining of 15 olive cultivars trained according to the high-density system were made in order to supply up-to-date information about the varietal behavior for adult orchards of this new cropping system. The mechanical pruning started at the end of the 6th year from planting and it was repeated for the following two years. Cultivar vigour affected pruning biomass and olive yield. Canonical discriminant analysis was performed to identify differences among cultivars. Medium-low vigour cultivars (Spanish and Greek) can be successfully controlled by mechanical and manual prunings without compromising their yield; instead, medium-high vigour cultivars (traditional and new Italian) require mechanical prunings to control canopy size, but this operation can hardly compromise their yield level and constancy. Further investigations are required to understand the right width of hedging to reach the correct equilibrium between vegetative and reproductive activity in adult orchards. At the moment, the correct varietal choice remains the only way to ensure the agronomical and economic sustainability of the high-density cropping systems, waiting for new results from breeding programs.

Moderate regulated deficit irrigation can increase olive oil yields and decrease tree growth in super high density ‘Arbequina’ olive orchards

A number of studies have found that ‘Arbequina’ olive oil yields in super high density (SHD) orchards are maximized at water application rates below 100% of full irrigation. To evaluate this relationship further, four regulated deficit irrigation (RDI) treatments ranging from 58 to 30% ETc were initiated about 70 days after full bloom and evaluated over 4 years. The experiment was located in two different soil types in the same orchard, a loam and a gravelly loam soil which significantly influenced water stress. Few significant differences were found between the different irrigation treatments; however, gravelly loam soils imposed significantly lower stem water potentials (SWP) than found in the loam soil. The loam and gravelly loam soils imposed a mild (ψstem=−1.6MPa) and moderate tree (ψstem=−2.1MPa) water stress, respectively, during the oil accumulation period. Oil yields were significantly greater and fruit yields were significantly lower in moderately water stressed trees versus the mildly stressed trees in 3 of the 4 years of the study. Moreover, oil percentages were significantly greater in moderately stressed trees months before tree harvest. A number of factors likely contributed to this increase in oil yield including: (1) improving the light environment for oil accumulation, (2) hastening fruit maturity at harvest, and (3) increasing fruit removal percentages from the trees. Tree growth was significantly decreased in the moderately stressed trees. Decreases averaged 36%, 67%, and 46% for shoot growth, trunk growth, and pruning weights, respectively, over the 4 years of the study. This resulted in a smaller, more compact tree in the moderate water stressed trees which facilitated mechanical harvest in SHD orchards.

IMPROVEMENT OF MANGO TREE ARCHITECTURE

This paper discusses the role of mango canopy architecture in mango productivity and orchard management and considers potential increases on production of high density orchards through improved canopy architecture. Lower tree height, reduced vigour and smaller more open canopies are recognised as important aspects of high density orchards. However, vigour management, light relations, flowering and crop load of high density orchards needs to be better understood if we are to developed sustainable highly productive canopy training and pruning systems that are easy to maintain at high planting densities.

Effect of rootstock on ‘Forelle’ pear (Pyrus communis L.) growth and production

European pears (Pyrus communis L.) are predominantly planted either on pear (P. communis) or quince (Cydonia oblonga L.) rootstocks. High-density commercial pear orchards require dwarfing rootstocks and the South African selections BP1 and BP3 were considered too vigorous. The growth and production of the important export cultivar ‘Forelle’ were evaluated on a range of rootstocks at three sites for between seven and nine seasons. In the final season, the trunk cross-sectional area (TCA) of trees on Pyrodwarf (PD), ‘Old Home’ × ‘Farmingdale’ (OHxF) 217, BU2/33, BP3, OHxF40 and BP1 averaged 100.0 cm2, with the smallest trees on Quince C51 (QC51). Trees on PD, OHxF217, BP1 and OHxF40 yielded 30.0 kg tree−1, whereas trees on Quince A (QA) and QC51 yielded <25.0 kg tree−1. Trees with a yield efficiency of 0.29–0.35 kg cm−2 TCA were on OHxF97, PD, QC51, OHxF333 and OHxF217, whereas trees on BP3 had a yield efficiency of 0.21 kg cm−2 TCA. Trees on OHxF217, OHxF40 and BP1 had a cumulative yield of 100.0 kg tree−1, whereas trees on QC51 and QA had a cumulative yield of 60.0 kg tree−1. The best rootstock was OHxF217, followed by OHxF40 and OHxF97. PD and OHxF333 also performed well but were evaluated at one site only.

Responses of olive tree yield determinants and components to shading during potentially critical phenological phases

Shading for short periods during potentially critical phenological phases can improve our understanding of the processes underlying the reductions in crop performance when solar radiation is limiting in high density orchards. Our objective was to evaluate the effects of three separate 30 day-long shade periods imposed during fruit set (FS), endocarp sclerification (ES), and early oil accumulation (OA) on some oil yield determinants and components in olive. Four shading levels (3, 20, 40, and 70% of incident photosynthetically active radiation; PAR) were applied in each period using shade cloths that surrounded one-half of large individual trees. Individual fruit dry weight, oil concentration (%) on a dry weight basis, and non-fruiting branch growth were determined at the end of each shading period, 45 days after their completion, and at the end of the season. The previously shaded- and the unshaded-halves of each tree were also harvested at the end of the season to obtain fruit number and oil yield for each half-tree. Individual fruit dry weight and oil concentration at the end of all three shading periods were decreased by shading due to reduced absolute rates of fruit growth and oil accumulation, respectively. However, at final harvest, there were no statistically significant treatment differences in individual fruit weight. By contrast, a small reduction in oil concentration persisted in the fruit from trees subjected to heavy shading during the OA period. Oil yield per half-tree at end of the season was decreased by shading applied during FS and OA periods, principally due to decreases in fruit number and oil concentration, respectively. Final oil yield was not affected by shading during the ES period. Elongation of non-fruiting branches was only decreased by shading during the early spring FS period, when vegetative growth was somewhat more sensitive to shading than fruit growth. Lastly, no consistent response of return bloom to the shading periods was detected the following spring. Our results suggest that the FS period when fruit number is defined and the OA period are more critical for determining final oil yield than the ES period. This information could provide guidance for the design of more effective management strategies in high density orchards where shading can play a key role.

STANDARDIZATION OF ROOTSTOCK IN MANGO

Rootstocks in mango are always seedlings whether they are of zygotic or nucellar origin. Clonal nucellar seedlings rootstocks have many advantages over heterogenous monoembryonic seedling rootstocks. Clonal rootstocks have been selected for specific soil types and stress tolerance and behavior of the scion cultivar on clonal rootstocks is highly predictable. With the intensification of fruit production due to socio-economic considerations, the role of rootstocks in commercial fruit production has increased considerably in the recent past. Although rootstocks have several applications such as improving fruit quality, imparting adaptability to climatic and edaphic conditions and inducing dwarfing, the priorities of rootstocks selection in the tropics and subtropics have been focused mainly on vigour management and securing regular high fruit yields. Mango is an important fruit crop of the tropical and subtropical regions. The yield is less than 10 t/ha in most of the growing countries. Low planting densities based on the expected eventual tree size, propagation on seedling rootstocks of unknown pedigree and irregular bearing habits are some of major reasons for low orchard efficiency of mangoes in India. In India and Mexico, monoembryonic seedlings are generally used as rootstocks. Polyembryonic ‘Turpentine’ seedlings are used as rootstocks in Florida. Either polyembryonic ‘Saber’ or ‘13-1’ seedlings are used as rootstocks in Israel. In Australia, ‘Kensington’ seedlings are used as rootstock. Throughout South-East Asia polyembryonic seedlings are used for rootstocks. Use of nondescript mango stones for multiplication of rootstocks has led to enormous variation in the performance of mango clones in the orchards. Some attempts have been made to standardize the rootstocks for various scion cultivars including the use of polyembryonic cultivars for vigour management, salinity drought, stress tolerance, fruit yield and quality. There are relative advantages of polyembryonic rootstocks in mango. In many regions including India and Mexico scion cultivars are still being propagated on heterogenous monoembryonic seedling rootstocks despite the demonstrated advantages of clonal nucellar rootstocks. The potential of clonally propagated manoembryonic rootstock has not been properly investigated. Other Mangifera sp. also have interesting attributes and should be screened for graft compatibility with mango. The species that could be tested as rootstock for mango might extend mango cultivation to areas where abiotic and biotic stresses currently limit production and could provide a better source for dwarfing rootstocks for high density orcharding.

EFFECT OF ROOTSTOCK ON GROWTH AND PRODUCTION OF 'FORELLE' PEAR: RIVERSIDE RESULTS

European pears (Pyrus communis L.) are planted either on pear (Pyrus communis L.) or quince (Cydonia oblonga L.) rootstocks. Modern high density orchards require dwarfing rootstocks, but the popular South African rootstocks, BP1 and BP3, tend to be too vigorous. Pear rootstocks are reasonably precocious with good compatibility and anchorage, while various degrees of incompatibility exist between pear and quince. The growth and production of the pear cultivar, ‘Forelle’ was evaluated on a selection of pear and quince rootstocks at four sites. Results from the Riverside trial site are presented here. After one year, trees on BA29, QA and BP3 were the tallest, followed by trees on QC51 and BP1, with trees on OHxF97 being the smallest. After two years, trees on BA29 and BP3 were the tallest (~250 cm), followed by trees on QA, then QC51 and BP1, with the smallest trees being on OHxF97. After nine years, trees on BP1 and BP3 had the largest Trunk Cross-sectional Area (TCA) (~109 cm2), followed by trees on BA29 (97 cm2), then OHxF97, QA and QC51 (~79 cm2). Trees on BP3 produced significantly higher kg/tree than trees on QC51 and QA after four years. After nine years, trees on QA had significantly lower yield (18.6 kg/tree) than trees on the other rootstocks (~24.6 kg/tree). After nine years, trees on OHxF97 (0.32 kg/cm2 TCA) and QC51 (0.32 kg/cm2 TCA) were more efficient than trees on BA29 (0.27 kg/cm2 TCA), QA (0.24 kg/cm2 TCA), BP3 (0.23 kg/cm2 TCA) and BP1 (0.21 kg/cm2 TCA). Trees on OHxF97 (0.93 kg/cm2 TCA) and QC51 (0.92 kg/cm2 TCA) had higher cumulative yield efficiencies than trees on BP1 (0.62 kg/cm2 TCA) and BP3 (0.68 kg/cm2 TCA). Principal component analysis PCA indicated that yield efficiency, OHxF97 and QC51 were closely associated. With a risk of incompatibility, OHxF97 could be an alternative for BP1 and BP3, or otherwise, BA29 and QC51 should be considered.

Environmental sustainability of different soil management techniques in a high-density olive orchard

Recent olive cultivation in Mediterranean Countries is characterised by the strong diffusion of high-density cropping systems and by the most environmentally conscious management regarding all the agronomic practices and the waste disposal as well. This research has investigated the possibility of the use of De-Oiled Pomace (DOP) as an eco-friendly tool for weed control in a high-density olive orchard providing an environmental comparison with other soil management techniques. Five methods of weed control have been compared in a two-year experimental orchard at the Bari University (Southern Italy): mulching with de-oiled olive pomace (DOP), nonwoven tissue (TNT) and polyethylene film (PEN), chemical (CHI) and mechanical (MEC) weeding, on the three most adapted to high-density orchards olive cultivars (Arbequina, Arbosana and Koroneiki). The data collected during the experimental test are submitted to an LCA (Life Cycle Assessment) analysis and five scenarios have been drafted based on DOP use and destinations.The results showed that the chemical wedding produced the greatest environmental burdens, and the higher environmental performances of DOP mulching scenarios for all environmental indexes, with burdens reductions and/or environmental credits. The presence in the following years of some biomarkers sensitive to macro and micro pollutants and heavy metals, in experimental plots mulched with DOP, confirmed the high environmental sustainability of this technique, excluding any kind of soil pollution in the medium-term period in the high-density olive orchard.

Heading cuts and prohexadione-calcium affect the growth and development of ‘d’Anjou’ pear shoots in a high-density orchard

Prohexadione calcium (P-Ca) has been shown to effectively reduce the vigor of pear trees. However, an analysis of the effects of P-Ca on growth and development of headed and unheaded shoots has not been performed. Therefore, P-Ca was selectively applied to dormant-headed (1/3rd removed) and unpruned shoots in a high-density ‘d’Anjou’ pear orchard in Oregon, USA. Both sets of shoots were treated with 250mgL−1 P-Ca in either a single or double application and compared to controls. The first application was delivered to shoots when ∼5cm of new growth accrued; the second, only if shoot growth resumed. P-Ca reduced shoot growth of both headed and unpruned shoots relative to their respective controls. Growth of unpruned shoots ceased 3 weeks following the first P-Ca application. In contrast, headed shoots required 6 weeks from the initial application to cease elongating. A markedly higher maximum shoot growth rate (mmd−1) was observed for headed shoots treated with P-Ca compared to unpruned shoots treated with P-Ca. At 87 days after full bloom, P-Ca-treated, unpruned shoots had a pronounced second flush of growth requiring an additional application of P-Ca. This growth resumption was 2 weeks earlier than unpruned, control shoots and 17d earlier than P-Ca-treated, headed shoots, for which only a negligible growth flush was observed. At the end of the season, unpruned shoot length was decreased by 28% and 41% for shoots treated with P-Ca once or twice, respectively, while headed shoots were 37% shorter than their controls (treated only once). The number of nodes and average internode length were significantly reduced for P-Ca-treated shoots, irrespective of pruning level, conferring a higher node density relative to control shoots. An increase in node density should result in higher yield efficiency once fruiting occurs on this wood. Heading, in contrast, increased the internodal space and decreased the number of nodes, ultimately decreasing node density. We did not observe any physiological effects on the growth or development of adjacent, untreated shoots originating from identical scaffolds as P-Ca-treated shoots. Collectively, these results implicate P-Ca as a powerful tool for precision-management of tree vigor in intensive pear plantings via selective treatment to areas of high vigor.

Quality Characterization of the Olive Oil from Var. Tosca 07® Grown in a Commercial High Density Orchard

AbstractA high density olive orchard represents a new planting system that requires cultivars with low vegetative vigor, such as Arbequina and Arbosana varieties. Different cultivars provide different performances in such orchards. This research was performed in order to determine the behavior of the new olive variety Tosca 07® in a commercial, high density orchard. The quality of Tosca 07® olive oils in three different maturity degrees during two crops seasons by physico‐chemical and nutritional characterization were compared with Arbequina olive oils obtained from trees grown under the same conditions. Tosca 07® is a very interesting olive variety for high density orchards. Because of its early ripening, it would be suitable for early harvesting, and this could be interesting for avoiding cold temperatures, frost, etc. Tosca 07® olive oils have also demonstrated a very suitable chemical composition in comparison with Arbequina olive oils, especially for their high content of antioxidant compounds (α‐tocopherol and pigments) present within the oils.

Water consumption of sweet cherry trees estimated by sap flow measurement

Sapflow was measured applying heat balance method on sample trees of a high density (spacing 4m×2m) orchard between the age of 4–7 years from 1 of May to 31 of August each year (2008, 2009, and 2011). Data from different 162 sample days were used in calculation of water consumption of sample trees and orchard. An automatic weather system was installed at the sweet cherry plantation to measure meteorological variables. The average daily water uptake of the 4-year-old trees were 24.2, 23.6, 22.7, and 10.9l from May to August in 2008, while in 2011 the 7-year-old trees transpirated in May 55.6, in July 48.4 and in August 44.8l per day. We found that the transpiration of trees in 4- and 5-year-old intensive sweet cherry orchard were 305mm and 320mm. The cumulative transpiration reached 523mm for 3 months in 2011, while for the whole vegetation period 700–800l water requirement can be calculated for local condition in intensive sweet-cherry orchards. The sapflow course showed typical characteristics on the investigated days with different weather conditions. The intensive water uptake began at about 6:00a.m. and slowed down to minimum between 20:00 and 22:00p.m. Transpiration of trees showed strong correlation to vapor pressure deficit, global radiation and air temperature, independently from the available precipitation. The crop basal coefficient (Kcb) – calculated as the rate of tree transpiration measured by SF and the referenced evapotranspiration – varied between 0.4 and 0.9. Our research results can contribute to harmonize the water supply and the plant's water use, and planning the irrigation.

The role of tree architecture in super high density olive orchards

Analyzing plant architecture is important for the understanding of plant growth, branching pattern, yield, and for the development of crop models. In other species tree architecture has been studied in detail, but not in olive. In this species, super high density (SHD) orchards (>1500 trees per hectare) have been extensively planted in recent years, using only a few cultivars (i.e. Arbequina, Arbosana and Koroneiki) considered suitable for this system. What makes these cultivars suitable for SHD orchards is not clear. In this work it is hypothesized that tree architecture plays an important role in this respect. We studied several tree architectural and reproductive parameters on different olive cultivars, including Arbequina, Arbosana and 19 others, mostly Italian. The impact of the architectural parameters on tree productivity was also studied. The architectural parameters studied were: diameter and node number of the trunk; number, diameter and angle of insertion of the lateral branches departing from the central leader; diameter, length, node number and average angle of fruiting shoots. On fruiting shoots, inflorescence and fruit number were also recorded respectively at bloom and at harvest. Branching frequency was calculated as the average number of lateral branches per bud. Arbequina and Arbosana differed from other cultivars for a greater branching frequency. The latter was negatively correlated to the diameter of lateral branches as well as to the diameter of one-year-old shoots. Consequently, Arbequina and Arbosana produced a greater number of smaller lateral branches and shoots, both parameters being desirable for SHD olive orchards. Combining branching and fruiting characteristics, we developed yield indices which segregated these cultivars from most others. The results suggest that high branching and small diameters are important architectural characteristics to increase yield efficiency, and affect the cultivar suitability for SHD orchards.

STUDY ON THE TRANSPORTATION PATTERN OF WATER AND SALT IN SOIL OF HIGH-DENSITY JUJUBE ORCHARDS UNDER DRIP IRRIGATION IN SOUTH XINJIANG

To reveal the pattern of water and salt movement with drip irrigation of high-density jujube orchards in South Xinjiang, soil moisture and salt contents were examined in the horizontal and vertical directions in key growing phases of Chinese jujube. The results showed that the salt contents displayed a descending trend in 0-40 cm soil layers and increasing-decreasing changes in 40-80 cm, whereas water contents in each soil layer presented a smoothly descending trend throughout the growing period. Before the drip irrigation was applied, water and salt contents increased with the depth of soil, and soil moisture in 40-60 cm was the highest. After irrigation, water contents became much higher with the increase of soil depth to the extent of 0-80 cm, but soil-salt in 0-40 cm reduced and soil-salt in 60-80 cm increased. In the horizontal direction, the salt contents were higher in the remote area from the water dripper. Such trends with the increase of soil depth weakened gradually to the extent that salt contents in 25 and 50 cm far from the water dripper were similar to the soil layer of 40-80 cm. Our results indicated that salt contents were rinsed to the outer edge of the wet body with water movement starting from the drip emitter, which resulted in a low salt zone in 0-40 cm soil layer.

Effects of Prohexadione-Ca, Ethephon, and Water Stress on Growth and Productivity of 'Golden Delicious'/M.9 Apple

Prohexadione-calcium (Pro-Ca), ethephon and transient water stress were evaluated in a factorial design, as potential inhibitors of early-season shoot growth of high density orchard management of apple (Malus domestica Borkh.) trees. In the experiment, water stress was imposed to one-half of the 7-year-old 'Golden Delicious'/M.9 apple trees in each of 5 blocks, by stopping irrigation for 3 weeks between 35 and 56 days after full bloom (AFB). Within each whole unit, the following Pro-Ca and ethephon treatments were randomly allocated at <TEX>$2{\times}2$</TEX> factorial: a) 0 or 250 <TEX>$mg{\cdot}L^{-1}$</TEX> a.i. Pro-Ca applied at 28 days AFB and b) 0 or 300 <TEX>$mg{\cdot}L^{-1}$</TEX> a.i. ethephon applied twice (35 and 71 days AFB). All trees were hand thinned to king flowers prior to treatments. Vegetative shoot growth was markedly reduced by Pro-Ca, with its effect being obvious within 14 days after application, while ethephon and water stress treatments were less effective. Pro-Ca had no effect on fruit set and yield but slightly increased fruit size. Ethephon substantially reduced the fruit size and yield but had no effect on fruit set. Water stress reduced fruit set, fruit size and yield. With regard to fruit quality, Pro-Ca did not influence fruit shape, flesh firmness and soluble solids contents (SSC) but slightly reduced titratable acidity. Ethephon had no effect on fruit shape but increased firmness, SSC and acidity, while water stress did not influence these fruit quality attributes. Dry weight of dormant spur buds was reduced by both Pro-Ca and water stress, while increased by ethephon. The larger dormant buds led to the larger spur flowers at the tight cluster stage the following spring. Return flowering was promoted only by ethephon, especially on previous season's shoots. There were no significant interactions between Pro-Ca and ethephon or water stress on most variables observed in this study.

Ripening indices and harvesting times of different olive cultivars for continuous harvest

This research was performed in order to assess the optimal harvesting time of four olive cultivars for continuous harvest, by following the seasonal changes of the most reliable ripening indices and by developing a model to find out the detachment index by the most quick colourimetric index. In the literature there are no works on these topics. A two-year field experiment was carried out in a super high-density olive orchard on Arbequina, Arbosana, Coratina and Urano® cultivars. Fruits firmness, detachment index, colourimetric index, pigmentation index, oil and polyphenol contents were compared and it used a model coming from a non-linear regressions to determine the detachment index by the colourimetric index. For all the cultivars the maximum oil content was observed in a more concentrated period with respect to the maximum mechanical efficiency, between the 60th and the 75th day after the start of the ripening process. Moreover the oil content maximum values occurred about 1 month after the maximum detachment indices. For Arbosana the relations between colourimetric and detachment index were not significant, both as a linear correlation and non-linear regression, because of the skin pigmentation occurred very slowly and never completely. So, it can be suggested to use the firmness or detachment index as reliable ripening indices for this cultivar. On the contrary, for the remaining cultivars colourimetric index could represent an useful ripening index. The sigmoid model could be reliable for the cultivars that veraison quickly, as Arbequina, Coratina and Urano® do.These first data collected on four cultivars could contribute to highlight their ripening processes and they could be useful for harvesting management in super high-density orchards. The ripening processes showed fundamental differences among the cultivars. Moreover, data obtained in this study are the first ones available in the literature for the new Italian cultivar Urano®. Our results emphasize the importance of setting a priority of criteria for choose the harvesting time for continuous harvest that will take into account first of all the maximum mechanical efficiency, so the maximum oil harvestable and then the maximum oil quality. The question on which better ripening index it could be used in order to detect the optimal harvesting time depend on the rapidity of the ripening process of a cultivar. The sigmoid model obtained is applicable only for Arbequina, Coratina and Urano®, for which it could represent a very reliable instrument to evaluate the optimal harvesting date.

Sprouts seasonal elongation of two olive cultivars in a high-density orchard

The new high-density cropping systems (>1200 trees ha-1) represent a very interesting proposal for olive orchard profitability. It is crucial to know the morphology and the dynamics of sprout elongation of a cultivar in order to fully assess its suitability for a high-density olive orchard. For this reason we planned a research on two cultivars, Coratina and Arbequina, in a high-density orchard. The apical sprouts elongation of Arbequina early stopped at fruit set without a further step, while Coratina showed a little growth flux after pit hardening. Similar trends showed the lateral proleptic sprouts. Only the sylleptic sprouts of both cultivars had a second period of activity. In all cases, the sprouts elongation finished at the end of summer, when oil accumulation started. Coratina showed higher apical shoot growth and internodes mean length than Arbequina. On the contrary, Coratina showed lower lateral proleptic shoot growth and nodes number than Arbequina, but the same internodes mean length. No significant differences were observed between cultivars for growth, nodes number and internodes mean length of sylleptic shoots. The differences observed between the two cultivars could be explained considering their different vigour. The introduction of this innovative cropping system is allowed to register a considerable reduction of production costs. The result is a considerable increase in the economic performance of the olive grove and a consequent reduction in the unit cost for kg of oil. These data are very useful for varietal choice and field management in high-density orchards and then for new olive breeding programs.

Ecophysiological response to irrigation of two olive cultivars grown in a high-density orchard

High-density oliveculture system needs irrigation and introduces new cultivars in new environments. So the evaluation of varietal ecophysiological response to irrigation is a crucial topic. For this reason it was planned a research on two cultivars, Coratina and Arbequina, trained according to high-density system. In 2009 the irrigation was conducted according to the conventional management by applying an irrigation frequency of 4 days. The leaf water potentials reached values similar to the limits reported for the recovery within 48 hours. However, plants showed a leaf water status and gas exchange recovery just after 24 hours from watering. The results highlighted some varietal differences: Arbequina showed a better response to irrigation, while Coratina performed a higher water use efficiency by a lower leaf transpiration.

Long-term leaf mineral nutrition in ‘Pacific Gala’ apple (Malus × domestica Borkh.) as affected by rootstock type and irrigation system during six stages of tree development

SummaryUse of an efficient rootstock and irrigation system are essential to establish a high-density orchard with a high production potential. High production becomes more important as World population increases and the availability of usable agricultural land and irrigation water decrease. Rootstock vigour and irrigation method are among the most important factors that affect the uptake of mineral nutrients and thus tree growth, fruit yield, and fruit quality attributes in apple (Malus × domestica Borkh.). The effects of four rootstocks and two irrigation systems on leaf size and mineral nutrition, and on the interaction between leaf nutrient concentrations, growth, and fruit quality attributes were studied over 4 years in ‘Pacific Gala’ apple. Evapotranspiration (ETc)-based irrigation scheduling, adjusted for the percentage of ground shading, was used for both the sprinkler and drip irrigation systems. Leaf calcium (Ca) concentrations decreased, but leaf potassium (K) concentrations increased with increasing rootstock vigour, resulting in the highest leaf Ca, but the lowest leaf K concentrations in trees on ‘Budagovsky 9’ (B.9) dwarfing rootstock. On average, trees supplied by drip irrigation had larger fruit and higher leaf magnesium (Mg) and manganese (Mn), but lower leaf Ca, K, zinc (Zn), and copper (Cu) concentrations than those irrigated using the sprinkler system. A significantly lower volume of water was applied to trees using drip irrigation than by sprinkler irrigation. Highlynegative correlations were found between leaf K concentrations and leaf dry weight percentages (DW%), between starch degradation pattern (SDP) and fruit firmness, between leaf K and leaf Mg concentrations, and between leaf K and leaf Mn concentrations. Highly-positive correlations existed between leaf N and leaf Fe concentrations, between fruit yields and leaf N concentrations, and among the concentrations of most leaf micro-nutrients.

Effect of Roots Pruning upon the Growth and Fruiting of Apple Trees in High Density Orchards

The influence of roots cutting on growth and fruiting of five apple cultivars ‘Gala’, ‘Jonica’,‘Topaz’, ‘Florina’, ‘Granny Smith’), under the climatic conditions of Cluj-Napoca, Romania, in 2009-2010, was studied. The trees were grafted on M9 rootstocks, trained as slender spindle and the orchardhad a density of 3174 trees/ha. Roots were cut twice annually, at 60 cm distance from the trunk and 30cm depth, as followed: first time, to the autumn fall leaves on one side of the row and the second time,in spring, at blooming time. The treatments had a strong influence, statistically assured, upon the shootgrowth, number of bearing branches, cumulative yield, trunk cross sectional area, the ratio of the yieldto a trunk cross-section. Root pruning reduced the average length of shoots. The longest shoots, inmean values, gave unpruned root variant (52.07 cm). Root pruning decrease the average length ofannual growth (29.47 cm). The biggest average trunks cross sectional area with the unpruned systemwere obtained (34.82 cm2). Also root pruning influenced the yield of the trees. The best cumulativeyield was obtained in variant of root pruning system (98.75 t/ha) followed by unpruned root system(97.8 t/ha). Finally, root pruning increased productivity. The biggest value in ‘Topaz’ with root prunedwas registered (1.79 kg/cm2). The lowest value of productivity index in unpruned system variant wasobtained.