Modern tree fruit orchards are planted with a goal of maximizing efficiency and productivity
When laying out a plan for an orchard, it is imperative to take into consideration the following: the position of the plot, terrain exposition, row direction, planting system, tree training system, cutting, and pruning system. All this enables the orchard to take advantage of the sunlight in the best way possible. Positioning the rows North-South enables the fruit trees to exploit the sunlight in an optimal way. Southern expositions and the terrains on top of the hills and slopes have more sunlight and are more efficient in exploiting its benefits. Valleys, ravines, gorges, and other similar places are not so efficient for maintaining the ideal levels of sunlight exposure.
Production of apple fruits, stone fruits, and nuts works best at yearly temperature differences between +35°C and -20°C. Biochemical processes in trees get disturbed in extremely high, as well as extremely low temperatures. The temperature drops as the latitude and altitude increase. Depending on type and variety, fruits of the temperate continental zone can be successfully cultivated up to 900 meters of altitude. Some varieties native to colder climates can change taste when cultivated in warmer areas. The sensitivity of fruit plants depends on various factors, such as the soil type, timing of winter, and/or early spring frosts, and type of rootstock to name a few. In the case of early flowering combined with colder weather, bees are not as active so insect pollination is deficient. Flower buds of peaches and apricot are more
sensitive to low temperatures than those of apples and pears. Late spring frosts should be taken into consideration in orchard planning. Low temperatures can also damage ripe fruit. High temperatures (35°C and above) can also affect the photosynthesis of the plant, as well as the development of the fruit. High temperatures can cause water stress. This leads to lower leaf turgor and also poor mineral absorbance from the soil, protein synthesis, and an overall slower metabolism. The influence of this factor can be neutralized by shading, smoking, and artificial rain, among other methods.
Most fruit will thrive in areas with atmospheric precipitation between 600 mm and 900 mm during vegetation time. The timing of rainfall during vegetation is equally important. Plants are especially susceptible to drought during flowering time, floral bud formation, and fruit development. On the other hand, excessive soil moisture is not favorable either. The most sensitive fruit types, in this case, are cherries, sour cherries, and apricots. Changes in precipitation alter the expected production outcome. Optimal atmospheric moisture is between 65% and 75%. Excessive humidity can lead to fungal diseases and weaker fertilization, while decreased humidity leads to higher transpiration, falling of fruit, and weaker fertilization. Therefore, both atmospheric and soil humidity should be taken into consideration in orchard raising.
The wind is an unfavorable climatic factor in fruit production. It dries out the soil, disables insect pollination, leads to the falling of fruit, and can cause branches and even trunks to break. Apples and pears with short stalks are especially susceptible to fruit falling. On the other hand, a light breeze can have positive effects, mostly on plants that get pollinated by wind, such as walnuts. It is important to choose areas that are sheltered from the wind or choose types and varieties that are more resilient to this climatic factor. Wind influence can also be minimized by raising windbreaks (shelterbelts).
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Orography encompasses factors such as altitude, exposition, the slope of the terrain, and proximity to water surfaces, and is in close relation to geographical latitude. Going further north, fruit prospers at lower altitudes. Different fruit types and varieties can possibly thrive, more or less, at different elevations. Terrain exposition is the position of the orchard towards the sides of the world and is conditioned by altitude and terrain slope. Southern expositions are warmer than Northern ones, regardless of their altitude. It is safe to say that apple fruit thrives best on Northern expositions, while stone fruit gives the best results on Southern expositions.
The slope of the terrain should always be taken into consideration when positioning the orchards due to the occurrence of soil erosions since landscaping can be costly. Mild slopes of 4-6% are suitable for fruit production. Water surface proximity has positive effects on the microclimate of the given area, and these orchards give higher yields, while the fruit is more intensive in color.
Soil properties such as depth, permeability, structure, mechanical and chemical characteristics should all be taken into consideration when planting an orchard. Sandy loam and loamy sandstone work best for fruit production. Chernozem is excellent for fruit orchards. Light soils and soils with too much clay are not suitable for high-production orchards. Heavy soils should be corrected, which is an expensive agrotechnical process. Fruit production on soils containing sand can be successful, especially when it comes to apple, cherry, sour cherry, apricot, plum, and pear, although with the increased use of fertilizers and irrigation measures.
Before orchard raising, chemical, physical, and biological analyses of the soil should be conducted. Special attention must be paid to hummus percentage and nutrients (potassium, phosphorus, and nitrogen), as well as to the soil pH value. The soil should consist of 3% of hummus, 15 mg P2O5/100g of dry soil, and around 25 mg K2O. If these optimal quantities are not contained in the land, agro meliorative reparation of the soil should be executed. Certain soil should be adapted to suitable fruit types and varieties. Dry, poorer soils should be paired up with more vigorous rootstocks and rootstocks that succeed on these types of land.
PREPARING THE SOIL
Modern orchards should be raised only on land adapted for such purposes. The land should be cleared of any undergrowth, weeds, roots, rocks, and similar, while the ground itself should get leveled to allow easier soil processing and prevent water accumulation in depressions. It is recommended for soils treated in this manner to rest for 2 to 3 years and/or to be used for leguminous plant cultivation, while orchard planting is not recommended directly after certain fruit and vegetable cultivation. Fruit should not be planted after strawberry, pepper, tomato, or potato, while it thrives well when planted after bean, soy, pea, crops, and other arable species. In case the soil has a lot of weeds and overgrowth on it, herbicides should be used during summer and the soil should be plowed. The number of insect larvae is also to be determined and insecticide applied if needed. Chemical analysis of the soil should be conducted before mechanical treatment. Amounts of hummus, easily accessible potassium and phosphorus, nitrogen, calcium carbonate, pH value of soil, etc. should all be determined. Analysis of microelement minerals content and mechanical composition of the soil should also be evaluated.
Modern, intense fruit orchard production requires at least 3% of hummus, 15 mg of easily accessible phosphorus and 25 mg of potassium, and at most 6-8% of calcium carbonate in total. Most fruit varieties require soil acidity of 5-7 pH, measured in KCl. If these requirements are not met, the correction of soil should be conducted. In the case of higher soil acidity, calcification should be carried out, and if the soil contains more calx, the soil is acidified with the use of gypsum, although it is a measure rarely needed. After organic and mineral fertilizers are spread, the soil is plowed, tilled, and undermined. The depth of plowing depends on the fruit variety, base, and soil type and reaches up to 40 cm in the ground. Soil is tilled usually from 40 to 70 cm of depth and undermining is conducted at a depth of 60-70 cm. Tilling is usually done in August and September, but under favorable weather conditions, this can be extended to October and even early November. It is best to do the tillage on medium moist soil, which should be left to rest and settle for 1 to 2 months after the procedure. After this, it is time for the fine preparation of the soil. Lately, undermining has become a common practice instead of tilling, especially when the plowing layer is shallow.
ORGANIZING THE LAYOUT
It is necessary to arrange the surface before seedling planting. This includes parceling, row direction, road networking, and fruit variety layout planning. If production is planned on a bigger surface, the parcels should not be longer than 230 m and wider than 300 m, which allows for easier harvest and other operations in the orchard. Main roads should be parallel with the rows and 6-8 m in width, while other roads should be 4 to 5 m wide. The entire orchard should be surrounded by a road at least 6 m wide which enables easier machinery manipulation.
During parceling, special attention should be paid to windbreaks, water supplies, and irrigation system regulation. After rough surface organization, planting spots are marked. In order to do this, it is necessary to know the spacing for different types and varieties.
SPACING BETWEEN THE TREES
Planting spots have to be marked as predicted by the project, and this includes tree layout (square, rectangle, triangle), as well as tree spacing in rows and in between rows. The spacing depends on the fruit type, variety, soil type, training system, etc. Trees can be planted in the shape of a square, rectangle, or triangle, the latter being the optimal one, since this way, the plants shade each other the least. Planting spots are being marked after soil preparation. The row direction should be north-south, as much as possible. The main row is determined first and it should lie on the longest side. In order to determine holes in other rows, lines parallel to the main row should be drawn on each side. A land surveyor should determine row direction and position on bigger surfaces, while on smaller ones this can be achieved simply by using ropes. After the spots are marked, one can start with the seedling planting. It is necessary to determine the selection and arrangement of varieties beforehand.
When selecting fruit types and varieties for orchards, special attention should be paid to the main fruit and its pollinizers, especially in self-sterile varieties. Pollinizers can be added to orchards even when the main variety is self-fertile since this leads to higher and more regular yielding and bigger fruits. Pollinizers should have good pollen germination, their phenophase of full flowering should match at least 50% with the phenophase of the full flowering of the main variety, their gametes should be compatible, the bearing of fruit should be approximately at the same time, and their longevity should be similar. When planning an orchard, the number of rows of each variety should be even, for easier organizing, protection, and harvesting.
In order to achieve easier protection, chemical thinning, picking, and other work in the orchard, raising plantations with one variety is advisable, or more varieties of similar resistance to main disease-causing agents.
RAISING MIXED ORCHARDS
Sometimes orchards contain more than one fruit type. Usually, walnut is combined with apricot, although other fruit can also be planted, such as peach, sour cherry, plum, etc. When walnut is raised as the only type in the orchard, stable and regular yields are expected 5 years after planting. As an example, the apricot is often planted in walnut orchards as an intercultural plant. It is assumed that apricot can be cultivated in walnut orchards for 15 or more years, that it starts bearing quickly, and is a wanted fruit. As the orchard ages, the majority of apricot trees will eventually end their life cycle, while the remaining trees are taken out when the walnut crowns get fully developed. It is necessary to point out that mixed orchards are somewhat harder to maintain, especially when it comes to protection, and it is not rare in practice that apricot trees grow faster and shades the walnut trees before they start bearing fully. Tree spacing in mixed orchards depends on soil fertility, variety vigour, provided agrotechnical measures, etc. Walnut can be planted, as an example, in an equilateral triangle layout, with 10 m between trees and 8.6 m between rows. Between two walnut trees, one apricot tree is planted, in each direction, at a distance of 5 m.
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TIME OF PLANTING AND PLANTING PROCESS
Fruit planting is possible anytime during the fall-spring period when weather conditions are favorable and the tree itself is in a dormant state. Fall planting works best because the grafts are forming stronger connections and the fruit is better ensured with water which allows for the seedlings to develop better and faster. Planting seedlings in the fall however does come with certain risks, such as freezing, damage caused by vermins and other wildlife, and similar. Spring planting is advised on windy terrain and areas with a moister climate, especially on heavier soil. It is also advised when seedlings with premature branches are used. Planting in spring should be carried out as early as possible, by April at the latest. If there is no possibility of irrigation after planting, spring planting can be more difficult. Saplings used for planting have to be healthy, they need to have a strongly developed root system as well as a strong overground part. Saplings should not be over 2 years old, except for special pre-formed trees like KNIP trees. For modern intense orchard saplings with premature branches are used, but not necessary. Before planting, all saplings should be individually prepared. This includes cutting off damaged, broken, and dry parts of the root up to their healthy parts. Longer root shoots are shortened to 15-20 cm in length. In the case of spring planting, it is advisable to keep the saplings in water (with the addition of insecticides and fungicides) for 12-24 hours. In other cases, saplings could be kept in a mixture of cow dung and loam with added copper preparation for disinfection.
If the soil is well prepared, if it is tilled or undermined, and the fertilizer is planned to be placed in the planting hole, then the holes for planting are to be dug in the dimensions of 60 x 60 cm. If the fertilization is already done and it is not planned to place the fertilizer in the hole, then the dimension of the hole of 40 x 40 cm is enough. Either way, the dimensions are to be wide enough to comfortably spread the root in the ground. The depth of planting should be the same as in the nursery and that usually means that the graft union must be above ground level, ideally 10-20 cm for apples but depends on fruit type and soil. When the roots are well spread in the hole a layer of fine soil is placed on the roots and well compressed so that the soil would stick to the roots. If fertilization is not done before, then after the roots are covered with soil, a 5-10 kg layer of well-dried cow dung manure can be placed, a layer of soil over that and be well compressed so that there is no air around the roots. If it is an autumn planting, then a soil hump is formed around the tree, and if it is a spring planting a small depression in the soil is formed and watered with 8-10 liters of water. When the soil absorbs the water, the depression is covered with soil to prevent evaporation. In modern orchards, immediately after the planting the irrigation system is installed and put into function. In this way the fruit trees are accepted by the soil much better, they develop faster and give fruit earlier.
Support systems (such as columns, wires, etc.) are used in orchards in the following situations:
- When low vigorous rootstocks are used, in case their root systems are poorly developed.
- When we aim for a specific training system form, such as palmettes.
- When the terrain is sandy or steep. Support systems are advisable in both cases, even on vigorous rootstocks, to prevent trees from curving.
- When we plant types and varieties that require support because of their growth habits, such as raspberries and blueberries, blackberries, and grapevines.
Metal or wooden columns are used. Their height reaches 2.5-2.8 m, while their width is around 10 cm. They are placed at a distance of 8-10 m from each other and 3 rows of galvanized wire are placed on them. The wire used on the columns is 3-4 mm wide. Reinforced concrete columns can also be used for this purpose. The marginal columns are 10x10 cm, while the inner ones are 8x8 cm in dimensions. Fruit saplings are planted after the columns are erected and anchored, cables are set up and the first row of wire is tightened. First, the planting spots are marked. This can be done by marking the wire with red paint or by using ropes at the distance that is predicted for the sapling planting. Columns and other components of the support system can be lifted after planting as well and even in fully developed orchards.
FLOOR MAINTENANCE IN THE ORCHARD
Soil maintenance in the orchard is important in the effort to reach optimal conditions for the root system to develop its full potential. Cultivating the soil in the given agroecological conditions we are establishing a balanced water, air, and heating regime so that all processes in the soil are developing optimally. The method of soil maintenance depends on various agroecological factors: the amount of precipitation, terrain slope, tree arrangement, rootstock, variety, training system, irrigation presence, etc. The most applied methods of orchard soil maintenance are clean cultivation and sod culture or sod mulch. Clean cultivation is used very often in orchards as it maintains the moisture in the orchard. The maintenance between the rows is done by the machines, and in the rows, the soil is farmed by hand, or tillers, or treated with herbicides. Autumn and early spring cultivation is done with a chisel plow in intense orchards. This way of maintaining the soil is the easiest for eliminating weeds, keeping the moisture in the soil, and an overall favorable water-air regime. The disadvantages are that the soil is weakened in structure over time, and it is necessary to fertilize the soil. So in modern orchards, every fourth-year soil is fertilized with manure or fertilizer grasses are sowed, that are plowed when they are in full flowering. In between rows, the grasses are sowed, and in the rows, between trees, herbicides are applied.
Modern intense orchards require proper and regular irrigation. This is even more important in areas that have less than 600mm of precipitation. Sandy, windy and southern positions require more water than structured soils and northern expositions. Less vigorous vegetative rootstocks also need more irrigation, due to their shallow root systems. Newly planted saplings, particularly when planted in late spring, require irrigation from the moment of planting. Irrigation depends on the precipitation of the given area. The first round of irrigation is usually done during flowering, which accelerates fertilization and the overall vegetative development of the fruit. Irrigation during these processes is vital because the highest percentage of
soil minerals (such as calcium) is directed toward the flower, that is, the fruit. Mineral absorption depends on soil moisture. Irrigation should be reduced or even left out during bud forming. There are several modalities of irrigation. The choice between these depends on terrain slope, soil type, financial assets, etc. Modern orchards require installment of irrigation systems before planting, especially during spring if saplings with premature branches are used, otherwise, plants may dry out or experience growth delay. The water used has to be absolutely clean in order for the system to work optimally. This is achieved by purification filters.
Pruning is done for the purpose of achievement of the desired training system, producing regulation, and plant rejuvenation. Based on the time of execution, we have summer or green pruning and winter pruning, done on mature plants. The main goal of pruning is to provide sunlight to all parts of the crown, as well as to achieve a balance between producing and vegetative growth. This pomo-technical operation greatly affects the height and quality of the yield. Its intensity depends on the fruit type and variety, age, number of buds, etc. It is important to keep in mind that weaker pruning results in faster and greater bearing, while more intense pruning results in higher vigour and slower bearing.
Winter pruning is extremely important and is done during biological dormancy, which is the period between leaf fall and bud formation. Pruning after this time negatively affects fruit development, although it can be done to reduce vigour in non-producing trees. It is also executed in types and varieties that flower early and can be damaged by late spring frosts.
Summer (or green) pruning is an additional measure executed in highly dense orchards with vigorous trees. Shoots that are overly vigorous and not necessary, as well as those unfavorably positioned, are being removed. This provides optimal conditions for bud formation in the next season and also helps bear more quality fruit. Removal of redundant shoots allows water and nutrients to be more efficiently used, while sunlight and air reach the inner parts of the crown with greater ease. Green pruning brings results only if done in a timely manner. Fruits are pruned after the active vegetative growth, usually in the second half of June and early July. When used for training system achievement, pruning is carried out when the shoots reach 5-10cm in length, which is usually in the first decade of May.