Stănică,F.
University of Agronomic Sciences and Veterinary Medicine, Bucureşti, Romania
Abstract
Fruit production in Europe had a fast evolution in the last two decades. Important changes occurred in the variety and rootstock assortment in all species. By introducing medium and low vigor rootstocks it was possible to increase the planting density even in fast growing species as stone fruits. The new high density orchards imposed a radical change of the orchard management and a new range of growing technologies. The innovations always started in the fruit nursery and recently, new typologies of planting material are proposed.
Soil preparation for the new orchards is sometime under the sign of the replanting problems due to the monoculture. New planting systems and tree canopies have been developed with the aim of better light use, ensuring high yield, high quality, but low training and maintenance pruning costs. In correlation, different hail and rain protection systems are in use. Grass cover soil management is generalized between rows, while on the row, herbicides or mechanical tillage is used. Fertilizers and irrigation are two important tools to control the tree growth and production. Generally, simple soluble fertilizers are applied with the irrigation water in function of the vegetation stage and plant needs. Depending of the production area, several systems of crop protection against wind, frost, hail, rain, birds are in use. Plant protection faces new challenges due to some specific requests of integrated and organic production systems, to the annual reduction of the approved pesticides number, to the rise of new pests and diseases and also due to the consumer concerns regarding fruit residues. Hand fruit picking is facilitated by self-propelled machines with fruit bins loading and downloading systems. For processing fruits mechanical harvest is largely used.
Continuous develop and innovation of orchard technologies in European fruit industry is requested in order to maintain its sustainability and competitiveness, by producing top quality fruits, with nearly to zero residues and no environmental negative impact.
Keywords: crop protection, fertirrigation, fruit picking, fruit tree propagation, plant protection, planting systems, soil management, thinning
Introduction
The evolution of the fruit production in Europe in the last century was marked by three important stages. The first one, a classic period, characterized by low planting densities of 300-400 trees/ha, high volume canopies (pyramid, leader, vase, etc.) ended in the 60’ by adopting some medium vigor rootstocks, as MM106 in apple.
The intensive plantations were realized by reducing the distance between rows at 4-5 m and by increasing the planting density to over 1,000 trees/ha. Typical hedge canopies as Italian palmete, Simple palmete, Fan palmete, but also low volume canopies as Slender Busch, Slender Spindle, and Spanish open vase have been introduced. The intensive orchards were managed using a special adapted range of tractors and machineries.
In the 80’ started the era of superintensive orchards with the high density apple orchards realized by the generalized use of low vigor rootstocks (M26, M9, M27). Planting systems as Super Spindle, Pillar System etc. brought the planting density over 8,000 tree/ha (Corelli
Grappadelli, 1997). There have been some tentative to further increase the planting density over 40,000 trees/ha in the biannual bearing “lawn system”.
After being promoted few years by nurseries, the very high density orchards trend diminished, especially because of the extremely high investment cost and of some fruit quality problems due to the bad light penetration. Some alternative canopy and planting systems as Drilling and Mikado, have been introduced (Widmer and Krebs, 1996).
In the last two decades, beside important changes in the variety and rootstock assortment in all species, the planting density stabilized between 2000 and 4000 trees/ha (DeJong et all., 2006). Even in the fast growing species as stone fruits, it was possible to increase the planting density by using medium and low vigor rootstocks. Rootstocks as Gisela 5 in sweet cherry, Ishtara in plum, apricot and peach produced a real revolution in the orchard planting systems.
New Fruit Technologies Nursery production
The fruit nurseries are generally the promoters of innovation and recently, new typologies of planting material are proposed. Stone fruits rootstocks are mostly in vitro micropropagated with all the benefits of this method: rapid propagation, uniformity, virus free, strong roots etc. Instead pomes fruits rootstocks are still propagated by traditional layering methods.
The first improvement of the planting material was the production of the feathered trees – knip. Even if initially, it was realized for apple trees, nowadays it is generalized for all the fruit species with multiple advantages on early fruit bearing and orchard establishment.
To reduce the number of planted trees/ha and so, the initial investment value, recently it was promoted by Mazzoni nursery in Italy, the Bi-baum® type of fruit trees. The trees are produced by double bud grafting with two vertical feathered axes, instead of a single one.
Micrografting is a new technique applied recently on large scale for the production of the pot grafted fruit trees. Using in vitro produced rootstocks, the micrografting is applied in January or early February under protected conditions. Scions start to grow and in late May or June, the potted trees are ready to be planted in the orchard. Until the winter time, the trees reach the high of 2.0-2.5 m. The method reduces the time of the production of grafted trees at 1.5 years, instead of 3-4 years and is applicable mainly to stone fruits.
In vitro micropropagation of varieties and cultivation on their own roots (without grafting) was successfully applied for some pear varieties (Stănică et all., 2000), kiwi plants, olive trees, walnuts (Navacchi et all. 2008) and is in the way to be extended for apricots, sweet cherries, peaches and other species.
Soil preparation
Sometime the soil for the new orchards has replanting problems due to the previous orchard monoculture. In that case, few supplementary measures are essential: removal of all roots rests of the previous crop; cultivation for 3-4 years with a legume crop, mainly
alfalfa or clover; one year cultivation with Tagetes sp. for soil restructuring and nematodes elimination (Ploeg, 1999); soil disinfection; fertilization etc.
In order to ensure good soil physical properties before planting is necessary a deep work with a ripper in two cross directions, at 60-80 cm depth.
Planting
Because of the high density and small planting distances between plants on the row, recently the trees are planted on open ditches (Figure 1). To increase the influence of the rootstock on the future tree growth and productivity, it is necessary to plant the fruit trees with the grafting point at least 20 cm above the ground.
Figure 1. Apple tree planting on open ditches
Planting distances are influenced by the species, the variety/rootstock vigor and by the canopy type (Table 1). Autumn is the best planting period for bare rooted trees. For potted trees planting can be executed during all the vegetation period, but is indicated to be finished before the end of June. After planting, fruit tree needs to be tide on the trellis system and usually, no pruning is applied. By exception, few vigorous lateral branches can be eliminated in order to balance the rapport with the tree leader.
Planting systems and tree canopies
Modern canopies and planting systems have been developed with the aim of better light use, ensuring high yield, high quality, and in the same time, low training and maintenance pruning costs (Sansavini and Corelli Grappadelli, 1997, Corelli Grappadelli and Marini, 2008.).
Introduction of knip-feathered trees have a major role on the orchard architecture and production:
- the single leader type canopies (Super Spindle, Vertical Axe, Solaxe etc.) have been generalized;
- fruits trees are full of lateral fruiting branches and fruit production starts in the first year after planting;
- under the fruit weight, the branches start to have a weeping position with a strong tendency for fruiting;
- pruning is limited to the elimination of the vigorous lateral branches;
Taking in consideration the fact that the new low vigor rootstocks have a superficial root system, usually a trellis system needs to be installed in order to sustain the fruit production.
In the same time, the trellis can be used as a support for the hail protection nets and for the drip irrigation pipes. After many years of orchard experience with the single leader canopies, some new canopies with double axe - Parallel V, or even triple axe – Trident, have been introduced.
Table 1. Tree canopies and planting systems for apple and pear
Specie Tree canopy Distance between
rows (m)
Distance on the row (m)
Trees/ha (no)
Apple Spindle (Vertical axe) 3.5-4.0 1.2-1.6 1500-2000
0.9-1.3 2000-2500 0.8-1.1 2500-3000 0.7-0.9 3000-3500 0.6-0.8 3500-4000
Mikado 3.8-4.0 1.6-1.8 1300-1500
Drilling 3.8-4.0 1.2-1.4 1700-2000
Solen 3.5-4.0 1.0-2.0 1200-2006
Pear Spindle (Vertical axe) 3.5-4.0 1.5-2.0 1250-1850
Palmete 3.0-3.5 2.0-2.5 1100-1450
Mikado 3.8-4.2 1.5-2.0 1100-1750
Drilling 3.8-4.2 1.2-1.7 1350-2550
Gard Belgian 3.0 -3.5 1.0-1.5 1800-2650
Drapeau Marchand 3.0 -3.5 1.7-2.5 1100-1600
The new type of double axe canopy (Parallel V) is recommended for the more vigorous varieties and species, because of the distribution of the growth energy on two directions.
Bi-Baum® tree type is ideal to form a double axe canopy by providing a balanced structure ready to produce fruits (Musacchi, S. 2008). Bi-Baum® was first recommended for apple (Figure 2) and pears, but there are some new researches for extending the system to the more vigorous stone fruits species.
Figure 2. Bi-baum® System (Double axis) at apple
Similar studies have been developed the concept of the Trident canopy, the trees having three vertical parallel axes (Figure 3). Even the first yield is obtained in the second year after planting, by reducing the planting distances three times, the initial investment diminishes.
Recently there are some approaches regarding the asymmetric orchard with interesting results regarding the light reception and tree photosynthetic efficiency (Losciale P. et all, 2010).
Figure 3. Trident (Triple axis) canopy at apricot Soil management
After decades of research on different soil management systems, grass cover is now generalized between the tree rows. Grass is obtained by seeding or by natural covering.
The most important advantages of the grass cover system (Figure 4) are represented by the positive effect on the soil structure, soil content in organic matter, soil microbial activity, orchard biodiversity etc. In the same time, the soil erosion, water loss, energy consumption and the man work are reduced. In grass covered orchard it is possible to circulate and to do typical works after heavy rains or hail.
Figure 4. Soil grass covered management
To control the weeds on the row, herbicides or mechanical tillage are used. In the conventional and in some integrated orchards, herbicides (mainly glyphosate based) are sprayed on a 0.8-1.0 m wide strip along the tree row (Stefan and Bucur, 2000).
In order to reduce the chemicals use, alternative methods of weeds control are applied.
One of the most efficient is the mechanical tillage on row made with different machines with trunk sensing device. The treatment is useful for soil aeration and for stimulation the roots growth in the depth.
Recently, some experiments have been done by covering the soil with reflective much.
Besides the advantages of artificial mulching, the reflective mulch has the main task to improve fruit coloration (Costa G,et al., 2003).
Fertilization and irrigation
Tree growth and productivity are influenced by some technical operation as pruning, root pruning and fruit thinning, but irrigation and fertilization are the most two important tools.
Based on the vegetation stage, plant needs and soil and plant agrochemical analyses, simple soluble fertilizers are applied with the irrigation water. The most important advantages of the method consist on direct root distribution and efficient use of the fertilizer, low energy request and low level of pollution.
Crop protection
Depending of the production area, several systems of crop protection against wind, frost, hail, rain, birds are in use.
Wind protection is necessary in windy areas, where the frequent winds can seriously affect the tree upright position and in the same time the fruit crop. Mixed species windbreaks are recommended to be planted around the orchard and even in the interior part of it. The windbreaks effectiveness on horizontal line is 10-15 times longer than the windbreak height. Within the windbreak different height species are planted from the smaller ones at the exterior to the taller ones in the central part.
Late frosts are serious challenges for early flowering species (stone fruits) but also, in some high altitude areas, for the normal flowering ones (apples and pears). One of the most diffused antifrost systems is the overhead irrigation but it needs a special knowledge regarding the timing, the water quantity etc. Other systems are using different air mixing devices as high tower wind machines or horizontal fans and recently, the mobile gas burners (“Frostbuster”) the work by the principle of energy transfer to the flower organs.
Hail protection is provided by the use of special plastic nets (Fig 5). If the initial hail nets were black, nowadays, the white ones (Crystal) are used. Hail net is installed normally on the same structure used as trees trellis, slightly modified and reinforced. The use of colored hail nets is still under research, different colors having different physiological effect (Vittone, 2006).
Figure 5. Apple orchard protected with anti hail net
Modified hail net by closing the lateral and the front side of the parcel is used frequently as a tool for orchard protection against birds especially in cherry. Many tests and research are in progress for replacing the hail net with an insect proof net in order to keep out and control specific orchard pests.
By using a special polyethylene transparent and reinforced fabric is possible to protect the orchard against rains. The technique is mainly used for sweet cherry and berries during the picking period in the rainy areas and it could provide also an earlier ripening (Figure 6). The trellis system in this case has to be stronger than the antihail one, by doubling the pole number and by a special anchorage.
Figure 6. Raspberry production under rain protection Plant protection
Plant protection is a delicate subject and a difficult task for the fruit grower. New challenges regarding some specific requests of integrated and organic production systems, the annual reduction of the approved pesticides number, the rise of new pests and diseases are imposed because of the consumer concerns regarding fruit residues (Zavagli 2008, Zavagli, 2011).
Some important prevention principles are recommended to be followed:
- mixed planting of resistant and less sensitive varieties, - orchard sanitizing and respect of hygiene rules,
- late and early treatments (dormancy period) to reduce the inoculums, - summer pruning etc.
Alternative fighting methods are requested:
- insect mass capture and male disruption by the use of pheromones,
- installation of light capture systems and use of other physical methods of combat, - biological control,
- use of repellent and insectproof bioproducts, - installation of insectproof nets,
In the same time, when applying chemical treatments, farmers need to consider seriously some important elements:
- treat only when necessary (by monitoring and prediction models), - use the best spraying technique (Loquiet et all. 2008),
- choose pesticides with shorter persistence or higher reporting limit,
- choose non toxic pesticides for birds, fish, honey bees, birds, warm blood animals etc.
- apply new chemicals more specific and less toxic,
- reduce doses (adapted to the risk, adapted to the canopy – EMR studies), - increase intervals between treatment and harvest.
Fruit picking
In order to establish the right moment for the fruit picking, some traditional and modern methods are used. The number of days from fruit setting till the ripening moment is normally known for every cultivar. Apart of that, different changes of fruit characteristics as base color, covering color, seeds color, taste etc, could indicate the approach of picking maturity.
Some more elaborated methods are analyzing the changes in the fruit starch content, by coloring the fruit section with iodine in potassium iodinate. Reduction of coloration because of the starch hydrolisation into soluble sugars, shows the fruit maturation stage.
Fruit flesh firmness evolution is also used to appreciate the ripening status, by using appropriate device called penetrometer. New undisruptive methods are proposed to determine the optimal picking moment. The NIR (Near Infrared) technique creates the possibility of analyzing some fruit biochemical parameters on the tree (Peirs, 2003).
A similar method was developed by an Italian research group of the Bologna University by creating a system of light absorbance measurement with the aid of DA meter (Costa et all., 2010).
For fresh consumption hand fruit picking is still the most popular. To facilitate it, self-propelled machines with fruit bins loading and downloading systems are used (Figure 7).
For processing fruits mechanical harvest is largely used. For processing in many fruit species, the mechanical harvest is applied (Corelli Grappadelli, 1988).
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Figure 7. Self propelled machine for fruit picking Conclusion
European fruit industry faces new challenges imposed by the necessity of maintaining its sustainability and competitiveness. Production of top quality fruits with nearly to zero residues and no environmental negative impact, requests the continuous develop and innovation of orchard technologies.
The future fruit production needs to be able to survive by reducing the inputs (specially the one based on conventional forms of energy), the man work and by adapting continuously to the climate changes and consumer needs (Bertschinger L., 2009).
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