Everything you need to know about apple cultivation, harvest and growth! Learn about: 1. Origin of Apple Tree 2. Climate and Soil Required for Apple Cultivation 3. Orchard Cultural Practices 4. Propagation and Rootstocks 5. Planting Operation 6. Flowering and Fruiting 7. Training and Pruning 8. Harvesting and Handling.
Origin of Apple Tree:
Apple is undoubtedly the most important temperate fruit. It excels the pear in its excellent keeping quality and wide variety of tastes and flavour. It is the premier table fruit of the world and has been under cultivation since time immemorial. The cultivated apples belong to the species Malus pumila or Malus sylvestris. It originated in South-West Asia.
In India, apple cultivation is extremely profitable, as is the case with grape-growing in the Hyderabad area and South India. Consequently, apple cultivation has become the major industry of Himachal Pradesh. Apple constitutes 2.7% of the production of major fruits.
Apple requires chilling below 40°F for a period of two or three months. Therefore, it is generally grown at elevations from 1,600 to 2,300 metres in India. Its cultivation in the Nilgiri Hills is not quite successful for want of enough chilling. In the Kulu Valley, which being situated deeper in the Himalayan ranges, is cooler, apples are grown at elevations as low as 1,200 metres.
However, when the temperature falls below 28°F, apple trees are injured by the cold. Several commercial varieties of apple, especially triploids like Baldwin, are self-unfruitful and require cross pollination.
Apple is generally propagated by budding or grafting on seedlings of crab apple, Golden Delicious, or Rus Pippin (Yellow Newton). The Red Delicious has a few seeds in each fruit but they germinate arid grow well Slued-budding with buds of current season’s growth is done in the month of June.
Tongue grafting is done at the end of winter. Several Mailing root-stocks developed in England are vegetatively propagated. They can be used to control the vigour of the plants. Seedlings as well as grafted plants of apple can be lifted in winter with bare roots.
The planting distance in India varies from 7 to 10 metres, depending upon the vigour of the plant. Generally, there is a tendency to plant the trees closer than is necessary. Planting is done late in winter after the danger of frost is over.
The pruning and training of apple are important. In India the trees should be trained by the modified leader system with three to five main branches and a clean trunk of about 1 to 1.5 metres. One-year-old plants are planted in late winter and are cut back at about 80 to 100 cm above ground. If branches are present at this time, only four to five of them ought to be retained and shortened in length.
No shoot is retained below 50 cm from ground. At the time of first dormant pruning the main scaffold branches are cut back to about half a metre in length. Secondary branches arise from the main limbs. Some of the new shoots, arising early in the second summer are rubbed off in order to develop only a few vigorous, secondary branches.
During the second dormant pruning, the crowded, misplaced or diseased secondary branches are removed and the extra vigorous ones headed back. This process is continued for four or five years, at the end of which there are eight to ten scaffold branches.
Recently, Spindle bush system of training has been found successful in Himachal Pradesh. It gives a small conical tree with central leader of only 2 m height and maximum diameter of 1.5 m. Horizontal fruiting laterals are trained from about 0.4 m above the soil.
With little pruning and the horizontal bending of laterals, these spindles start fruiting early. The tree is grown on dwarfing root-stocks such as M-9 except for Spur type cultivars where semi dwarf rootstocks M-7 or MM-106 are recommended.
In U.K. meadow orcharding has proved successful. In this method the plants on dwarfing root stocks are headed back close to the ground and a large number of lateral shoots develop. These are sprayed with growth retardants like Alar to induce early flowering. These are cut back after fruiting.
The pruning of bearing trees is important to maintain a balance between vegetative growth and fruit-production. Too much vegetative growth results in poor fruiting and the absence of vegetative growth reduces the crop in the subsequent year. With proper pruning, the branches of a young tree should make an extension growth of about 25 to 50 cm every year.
Older trees should make half this extension growth. Some apple varieties bear fruit on short crooked growths called spurs. The spurs bear fruit for several years. Such varieties require little pruning. Varieties bearing- fruit on young shoots require more pruning to encourage new growth of branches.
Older trees require more pruning than young ones. Thinning of the fruit is also practiced in order to improve fruit colour and fruit size. It is desirable to leave about one fruit for every 40 leaves. This spaces the fruits about 15 to 20 cm apart and there is only one fruit per spur.
It is being recommended that in an orchard of average fertility, N, P and K should be applied in the ratio of 70: 35: 70 g per year age of the tree. The dose may be stabilized after 10 years of age (700 g + 350 g: 700 g). These applications should be supplemented with 10 kg of FYM. The fertilizers should be applied at three stages i.e. a fortnight before the expected bloom, three weeks after petal fall and the end of July.
Recently deficiency of magnesium and micronutrients like boron has been experienced and the associated disorders like islands of chlorosis in leaves and corky core in fruit. This can be corrected with a spray of Magnesium sulphate (1 to 2%) and Borax (0.1%).
However, in the Kumaon area, the application of nitrogen and potash does not seem to improve the performance of the trees. For distant markets the fruit is harvested in advance of full maturity. Harvesting is in full swing in September-October except in the Nilgiris, where the season is from April to July.
The harvesting of different varieties starts from June and continues upto November. Each tree is harvested in three installments. The harvested fruit can be stored for about three to four months at room temperature in a temperate climate. In cold storage at temperatures of 0° to 1.6° C and 85-90% of relative humidity varieties like Ambri and Red Delicious can be stored upto eight months.
However, practices which increase Ca level in fruit can decrease Ca related disorders in apple. Spray of 0.5 per cent calcium chloride (5kg/100 litres of water) starting from first/second week of July and repeated at 15 days interval for at least three times-will control bitter pit and other calcium related disorders. Addition of Bavistin (0.05%) in spray solution of the last spray remarkably reduces the incidence of blue mould (Penicillium expansum Thorn). Besides, Boric acid spray (0.1 to 0.25%) effectively controls superficial scald of apples.
Ethylene generating chemical ethrel (2-Chloroethyl phosphonic acid) at the rate of 500 to 1200 ppm hastens fruit maturity and intensity of fruit colour. Lower concentration hastens fruit maturity by 10 to 14 days and higher dose by 5 to 7 days. The spray should be done a week prior to expected harvest time.
Alar (1000 ppm) sprayed 60 days before harvest delays the ripening and improves the storability of apples. Early varieties have a shorter storage life.
The problem of pre-harvest drop is more severe in early cultivars like Mc Intosh, and Tydeman’s Early Worscestor, where 40% to 60% of the fruits drop. In mid-season cultivars viz Red Delicious, Royal Delicious and Golden Delicious the pre-harvest drop is 15 to 20 per cent. Spraying with NAA (20 ppm) three weeks before harvest reduces the pre-harvest drop. Other chemicals like 2, 4, 5-T (20 ppm) and 2, 4, 5-TP (15 ppm) are also quite effective in controlling fruit drop.
Fruits are graded according to their size, weight, shape, colour, soundness and maturity etc. Size grading is essential for uniformity and packing in standard cartons or boxes. There are usually 7 size grades (super, extra-large, large, medium small, extra small and, pitto) of apple. Each wooden box is lined inside with newspaper sheet keeping the margin for overhanding the flaps.
Climate and Soil Required for Growing Apples:
Apple has diverse temperature climatic adaptation. It is the most widely planted fruit of the temperate zone. Most of the apple varieties require 1000-1500 chilling hours below 7°C to break the rest period. These conditions are available at an altitude ranging from 1500-2700 m above mean sea level. The average temperature should be around 21-24°C during the active growing season. Low temperature rains and cloudy weather hamper bee’s activity during pollination.
Abundant sunshine is important in growing apples since it is largely responsible for good colour development. In general, sites located in north eastern aspect at lower altitudes and south western aspect at higher altitudes is suitable for apple growing. The localities should be free from hail storms and spring frosts. For optimum growth and fruitfulness, apple trees require 100-125 mm of rainfall equally distributed over the growing season.
Apple trees are particularly sensitive to low soil moisture supply. Water stress during growing season reduces number and size of fruits and increases June drop. Excessive rains and fog at the time of fruit maturity deteriorate the fruit quality and increase the incidence of sooty blotch, fly speck and other diseases. High winds are not desirable for apple cultivation. Abundant sunshine is important for the growth development of apples and is responsible for high colour in fruits.
Apple can be grown on all types of soils. Proper drainage and fertility of soil are important. Most suitable soil for apple is deep and well drained loams. Loamy soils, rich in organic matter with pH ranging from 5.5 to 6.5 and having proper drainage and good aeration are most suitable for apple cultivation. The soil should be free from hard substrata and water logging conditions.
Water logged soils favour soil borne diseases particularly collar rot and root rot. When apples are grown on calcareous soils, they suffer from iron and manganese deficiencies. Apple suffers from potassium and magnesium deficiencies if grown on light soils. Soils with heavy clay or compact sub soil should be avoided for planting apples as in clay soil; most roots slope downwards and grow in sub-soil.
Orchard Cultural Practices for Apple Cultivation:
i. Irrigation:
Water requirement of an apple tree varies according to climatic conditions, types, age of the trees and its different stages of growth and development and management practices. The very first irrigation is done just after planting. The further irrigations are done to provide adequate soil moisture so that young plants do not suffer for want of adequate moisture. Due to lack of moisture plants show stunting effects of their growth.
During the period from June/July to September, it is necessary to irrigate the apple plant for proper fruit development. Irrigation before June is also necessary, particularly for newly planted trees, especially those on shallow, light or gravelly soils.
The water requirement of Starking Delicious apple grafted on M 7 rootstock was worked out and irrigation was applied at different levels of field capacity (75, 50, 25%). It was observed that 8 irrigations were needed in total to the trees irrigated at 75% field capacity. However, only 3 irrigations were applied to the trees irrigated at 50% of the field capacity, 2 irrigations at 25% of the field capacity and 1 irrigation to the control. The quantity of water applied was 212, 429, 646 and 212 litres per tree at 75%, 50%, 25% field capacity and in control, respectively.
The consumption of water by an apple was estimated to be 127, 113, 108 and 94 cm/acre when irrigated at 75, 50 and 25% of the field capacity and control. The consumption of water was low in early growth stages (March – April) of tree and fruits. It increased from May onwards the period corresponding to greater foliage and rise in atmospheric temperature. The peak water consumption reached in July just before harvesting of fruits. During the period from July to September, irrigation is important for fruit development. For newly planted trees, irrigation before June is also necessary particularly on shallow, light or gravelly soils.
The modern systems of irrigation, like, drip, sprinkle or trickle have been proved very effective with respect to plant growth and fruit yield in apple. Through drip irrigation, nitrogen fertilizer can easily and economically be given. This system also suits the trees on hill slopes. Water consumption and soil losses through erosion are considerably less than with furrow irrigation. Drip irrigation at 100, 80 and 60 per cent ETC to Scarlet Gala and Red Fuji was found to enhance vegetative growth compared to basin irrigation. The growth increased with volume of water applied through drip. The yield was improved with 100 per cent ETC.
ii. Intercropping:
Intercrop for apple orchard should be well planned, beneficial and profitable. Crops should be selected for intercropping in apple which does not interfere with normal irrigation and other management practices. Intercrops should not encourage incidence of insects and diseases. The crops such as melons, beans, strawberries, etc. are preferred as intercrops. Forage crops can also be raised between the rows of young plants. Sometimes, filler trees between apple trees are also planted. Thus, income is obtained earlier and the trees are rather easily removed when crowding seems apparent.
iii. Orchard Management Practices:
The tree growth, yield and fruit quality is greatly influenced by orchard soil management practices. The most suitable system of soil management for a particular area, however, depends largely on type of soil, amount of precipitation, topography and planting system.
Clean Cultivation:
The whole area between the trees is cultivated during the first initial years of planting. During the summer months cover crops are grown and ploughed into the soil afterwards. Clean cultivation is found suitable where the slope of the land is less than 10 per cent. This system, however, reduces the uptake of phosphorus and potassium following damage to tree roots in the surface soil.
Sod Culture:
The various grasses and legumes are grown as a permanent cover. The grasses are cut when 7-10 cm high and left in the orchard for decomposition. This system is followed where the slope of the land is more than 10 per cent. This system is popular in Kotgarh orchards. The fruit colour is improved through Sod culture system. Soil erosion is prevented and penetration and percolation of moisture into and through the soil is facilitated. Scab control is difficult since infected leaves from the previous season do not easily decompose.
Mulching:
Mulching improves soil moisture conditions and tree growth with respect to trunk diameter and shoots length. In Himachal Pradesh, where most of the orchards are rainfed, use of mulches particularly, in areas affected by summer drought, can greatly reduce the water losses from the soil and further improve the availability of nutrients. Straw, hay, sawdust, composted conifers, farmyard manure, and black polythene are mostly used as type of mulches. Mulching encourages development of roots near the surface and increases the availability of K, N, P, Ca, Mg and B in the soil. The system’s demerit is that frost damage to the blossoms is slightly increased due to insulating effect of straw mulch.
iv. Weed Control:
The use of herbicides to eliminate weeds and grasses enables tree roots to exploit the surface soil more effectively than in grassed or cultivated orchards. Apple orchard sprayed with glyphosate at 1.7 kg/ha or mechanical weed control showed considerably higher yield than trees on unweeded plots. Hexuron 80 WP (diuron) @ 4kg + glycel 41 SL (glyphosate) @ 0.8 l/ha control the broad spectrum of weeds effectively in apple orchards.
Application of 10 – 15 cm thick grass mulch + glyphosate @ 800 ml/800 litres water per hectare provides acceptable level of weed control in apple orchards. In higher hills, black polythene has also been found effective for checking weed growth.
v. Manuring and Fertilization:
The doses of manures and fertilizers depend upon soil fertility, type of soil, kind and age of the tree, cultural practice and climate.
In fertile and rich soils, doses can be reduced by one-third to one half. In Arunachal Pradesh 50 kg FYM, 350 g N, 180 g P2O5 and 180g K2O is recommended. To full grown apple tree, the doses of fertilizers in Tamil Nadu are scheduled as 25 kg FYM, 250 g N, 1 kg P2O5 and 1 kg K2O.
Farmyard manure along with phosphorus and potash should be given during December- January to the bearing trees. Nitrogen is applied 2-3 weeks before bud break. When irrigation facilities exist, nitrogen can be applied in two split doses and the second half can be given one month after flowering. Complete NPK fertilizers should be applied as a single dose during February. In Himachal Pradesh, the retention of phosphorus in soil is good, therefore, its excess application should be avoided.
The phosphours should be applied after three years under such conditions. The fertilizer should be broadcasted on the soil surface under the spread of the trees and slightly mixed with the soil. Fertilizers should be applied at least 30 cm away from the trunk in old trees and should not be applied in too wet or too dry soils. In high rainfall areas with steep slopes, band application of nitrogenous fertilizers should be preferred.
Propagation and Rootstocks:
Apple is mainly propagated by grafting and budding. The rootstocks are raised from the seeds of selected hardy varieties suitable for this purpose. For raising seedling plants, the seeds are stratified in sand at a temperature of 4-7°C for 60-90 days. Stratification can also be done by direct sowing of the seeds in the nursery in early December.
Seed after stratification are sown in February-March at a distance of 5 cm in rows 10 cm apart. The seedbeds are covered with mulch in order to protect the germinating seedlings from heavy rains. The seedlings can also be raised in polythene bags or in earthenware pots. The seed can also be stratified for 2-3 months at 2-5°C.
Clonal Propagation:
The clonal rootstocks are propagated by mound layering. The clones are planted at distance of 30 cm in rows 60 cm apart during winter which give rise to numerous shoots in the spring. All these branches except the central one are ringed before treating with Seradex during the rainy season to encourage the root development. The ringed shoots are then covered with soil and the rooted clones are separated at the onset of dormancy and planted in nursery beds for further grafting.
Rootstock M 27, M 9 and M 26 has weak anchorage. MM 106 is susceptible to collar rot. MM 111 is resistant to drought. M 25 is precious. The cross are as M 26 [M 16 x M9], MM 106 [M2 x Northern Spy], MM 104 [M2 x Northern Spy], MM 111 [Northern Spy x Merton 793], and M25 [Northern Spy x M2]. Six hardy clonal stocks are produced by Ottawa Research Station, Canada. Ottawa 3 is a dwarfing rootstock.
The performance of apple trees in Himachal Pradesh is less satisfactory on clonal rootstocks on account of low fertility status of the soil, sloppy lands and inadequate irrigation facilities. The Crab apple seedlings (Malus baccata), is widely used as rootstock. Seedling rootstock can also be raised from seeds of scion cultivars. Seeds of Ben Davis, Delicious, Yellow Newton, Rome Beauty, Mcintosh give good germination.
Grafting and Budding:
The rootstocks are grafted with desired scion variety during February-March. Usually tongue grafting gives a good success and is performed about 20-30 cm above ground level. Seedlings which fail to show success with tongue grafting, shield budding should be done in the month of June and chip budding during mid-March. Old trees can also be top-worked. Rootstocks have influences on scion with respect to tree size, vigour, cropping and precocity. The intensity of fruit colour, and flavour are also influenced favourably.
The effect of certain scions has also been recorded on rootstocks with respect to volume of roots, their direction and colour. The uniformity and vigour of resultant apple trees are obtained on rootstocks of the varieties viz. Delicious, Rome Beauty and ‘Wine Sap’. Mailing 9 rootstock has dwarfing effect which is used in home gardens where dwarfing is desirable. However, none of the known varieties is completely resistant to wooly apple aphid. Apple rootstocks are easily propagated by hardwood cutting with the aid of growth regulator like IBA at 2500 ppm.
Planting Operation for Growing Apples:
While planting an orchard, proper decisions about the selection of varieties, rootstocks, tree size and spacing, pollination and planting procedures must be made with understanding. The commercial bearing life of a standard apple orchard has been estimated about 50 years.
The pits are dug on well cultivated land during summer in the month of April-May in advance of planting. Generally the dimension of pit should be kept 1 x 1 x 1 m but on rich and deep soil, it may be kept 60-75 cm3.
On steep slopes, the tree rows are planted along the contour to avoid excess erosion and improve safety in operation of equipment. Apple planting is done with its one year old plants during the dormant period preferably in the early spring avoiding low temperature injury. Planting is done in square or hexagonal systems. Planting is done from December to March. However, early planting in December – January is desirable.
The planting distance varies according to variety, the vigour of rootstock, the fertility level of the soil and general climatic conditions of the area. The planting distance is kept 3.0-7.5 m under different conditions. Too close planting should always be avoided; otherwise it will cause many problems like shading, root crowding, less availability of nutrients and moisture, hindrances in cultural operations, difficulty in pest and disease control. The grafts should be planted in such a way that the point of their union remains 25 cm above ground level to prevent from incidence of collar rot.
Flowering and Fruiting:
The time of flower bud initiation in apple is closely related to the growth cessation of shoots on which they are set. The period ranging from growth cessation upto the appearance of floral primordia is the period of physiological differentiation of flower buds. During this period, differentiation processes proceed within the buds, increasing in number of nodes and inducing some physiological changes. When the bud reached a certain stage, it may become a flower bud or may terminate its differentiation becoming a leaf bud.
The fruit buds are usually developed on spurs, laterally on two/three year old wood. However, buds may also develop on tips of one-year old shoots, which are found mostly when dwarfing rootstocks are used. A good correlation was found to exist between the leaf area and flower bud formation. In cvs like Granny Smith and Delicious, no flower bud formation was found at leaf/fruit ratio below 10 which was found to increase progressively by increasing the ratio from 20 to 50.
The average maximum and minimum temperature around 20° and 10°C, respectively during flowering in April in Himachal Pradesh resulted in good fruit set. High relative humidity (more than 50%) in March delayed flowering without affecting fruit set, but high rainfall and relative humidity during flowering in April adversely affected fruit set, while low rainfall and relative humidity in April improved fruit set and yield. Very low temperature i.e. less than 4.5°C reduced fruit set by interfering pollen germination and bee activity. Sprays of aminoethoxyvinylglycine inhibit ethylene production and increase fruit set in treated apple flowers, suggesting that endogenous ethylene level limits fruit set.
A continued enlargement of the receptacle takes place during the development of the fruit. The throat of the receptacle becomes narrow through which the style protrudes. The connection between the receptacle and carpel tissues becomes so close one that the receptacle makes up the greater portion of the flesh of the apple. A rapid phase of cell division occurs in the first few weeks after pollination which ceases abruptly 30-40 days after full bloom in Cox’s Orange Pippin, and after 4 weeks in Granny Smith.
The subsequent fruit growth occurs mainly due to cell expansion. The fruit growth pattern follows a smooth sigmoid curve. In apple, fruit growth is dependent on the presence of growing seeds up to the end of the June drop. After this stage, removal of the seeds no longer results in cessation of fruit growth.
The water content in apple fruits varies from 75-90 percent. The water content increases with the increase in fruit size with a slight decrease towards the end of maturity. The bulk of the carbohydrate in fruit is sugar which is mainly synthesized in leaves and transported to the fruits although, a very little sugar is also synthesized by the fruit. Fructose, glucose and sucrose are the three main sugars found in the fresh apple. The reducing sugars (fructose and glucose) and sucrose content of the fruit increases with the increase in fresh weight.
Light and temperature during the first four months after fruit set have a marked effect on sugar content of fruit. Starch accumulated at very early stage of fruit development. The accumulated starch is hydrolyzed into sugars with the advancement of maturity. The disappearance of starch is higher at the later stages of fruit development. The titratable acidity of the fruit steadily decreases as the fruit matures but the actual or absolute amount of acid present in the fruit increases until just before harvest when it decreases slightly.
Training and Pruning of Apple Trees:
Pruning is done with a view to giving desired shape to a tree during early growing years and is termed as training. Even after proper training, the yearly pruning of bearing trees is quite important so that it could support a full crop of large and coloured fruits during the subsequent bearing period.
A. Training of Standard Trees:
These are trained according to modified leader system. A leader develops on the young tree until it reaches the height of 2-3 m when the growth is restricted. The plant is pruned 60- 90 cm above ground immediately after planting.
First Year Summer Pinching:
The scaffolds are selected at equal distance with the lowest branch 30-60 cm above the ground and the others are spaced vertically at 10-15 cm apart. The growth of retained scaffold may be encouraged by depressing the growth of other shoots by pinching the top 3-5 cm of other shoots. Summer pinching is done from mid-April to mid-May or when the shoots are 10 to 20 cm long.
First Year Dormant Pruning:
This is done in winter following the first summer growth. Three scaffold at equal distance should be selected preferably with a vertical spacing of 10-20 cm. The primaries are headed back to achieve a balance in growth among them.
Two good limbs available may be headed back to 45 cm from the trunk to suppress their development until a third scaffold can be selected at the end of second growing season. Cut the laterals back to one bud and defer scaffold selection until the next year. Such trees will generally grow vigorously and will benefit by summer pinching during the second growing season.
Second Year Dormant Pruning:
In second dormant season 5-7 secondary branches per tree usually two on each primary scaffold are selected. These secondaries are directed partially outward. New growth from such branches will fill in laterally giving the tree a well-shaped framework. Secondary limbs should be left full length until it is necessary to maintain balance with the primaries or other secondaries.
If the primary scaffold branches are over-vigorous, it can be retarded by heading back to balance with the rest of the tree. Most trees will produce short laterals and spurs during the second year and these should not be immediately removed as these provide shade and some early fruit.
Third Year Dormant Pruning:
This consists of thinning and removal of unwanted branches and cutting others to desirable side limbs. During the third growing season, secondary branches often form fruit spurs, but on young trees fruit bud may be found at the tip of unpruned shoots.
Fourth Year Dormant Pruning:
By this time, training has been largely completed. The tree should be thinned out and the remaining branches cut to side limbs. A moderate number of small shoots should be left in the centre of the tree for fruit bearing wood. Adequate thinning out of branches and fruiting wood will maintain a well distributed bearing area throughout the tree and reduce excessive spread and breaking of branches. By fifth summer after planting, most apple varieties produce enough crops to be considered a bearing orchard.
B. Training of Dwarf Trees:
Spindle bush, Dwarf Pyramids, Palmets, Head and Spread and Cordon methods are followed for training dwarf trees. Head and spread system for central leader tree is also adopted for moderate and ultra-high density plantings. Spindle bush is found most suitable method. In this case one year old apple plants are cut back to a bud about 60 cm above the ground.
First Summer Pruning:
This time 2-3 laterals 30 cm from the base may be used to form the main scaffold branches. Such laterals should have a wide angle with the main stem and should be spaced at equidistance around it. The vigorous growing laterals are tied down in August. The ties can be removed after leaf fall or left till the following summer. They should be tied so that they are straight, not arched, otherwise strong vertical shoots will arise from the top of the arch.
First Winter Pruning:
Two or three well-spaced laterals should be retained and unwanted branches arising on the main stem should be removed. The scaffold branches may be cut back by one third to half of their length to an outward growing bud if the growth is weak. Otherwise the main branches should not be pruned. The vigorous upright growing shoots arising directly below the shoot forming leader and competing with it should be cut.
Second Summer Growth:
During the third summer, spindle bushes may carry a fruit. During August of the second year suitable laterals are tied down to form branches.
Second Winter Pruning:
To check excessive vigour of the central leader it may again be cut back to the next suitably placed rather weaker growing lateral which is tied and trained to take the place of the central leader. Delaying pruning until late winter or early spring will also help in checking vigour.
Pruning:
When the pruning of bearing tree is done the main purpose is to maintain a proper balance between vegetative growth and fruit production. An ideal mature tree should produce at least 25 cm of new terminal growth each year. Thus, the tree increases and maintains its fruiting area while producing satisfactory annual crops.
The trees receiving regular pruning require light thinning and cutting back of the terminal branches to laterals. This prevents the tree from getting too high for economical spraying and picking operations.
The centre of the tree should be kept fairly open to impart better colour to the fruits. If this is not practiced for several years, it is best to thin out surplus branches over a period of two or more seasons. Heavy pruning will encourage vegetative growth and expose scaffold branches to sunburn damage.
Old bearing trees producing small fruits will benefit from heavy pruning which stimulates new shoots and fruiting spurs. The larger pruning wounds should be protected by covering with Bordeaux paste and Bordeaux paint.
In standard trees start pruning from the top of the tree and work downwards. The upward growing limbs should be cut back to strong laterals. Remove the crowding branches and thin the remaining limbs, leaving the vigorous fruiting wood well-spaced along the length of the limbs. Remove diseased, dried and broken branches. Remove large limbs if growing parallel and crowding other limbs.
While making large cuts direct sun light should not sunscald remaining exposed branches. Remove all water sprouts except needed one. While removing a thick side branch, the first cut should be made on the under-side of the limb where the weakest wood occurs. Thin out the interfering branches growing upward from the top of the limbs. Divert branches to open areas by pruning back to desirable laterals.
In dwarf trees, once the central leader has reached its allotted height of 2.5 m, the extension growth should be cut back each year to a weaker side branch. The strong growing shoots and branches towards the top of the tree should be removed completely. Renewal pruning of the fruiting branches lower down should be carried out each year for maintaining the vegetative growth and fruit quality in the lower parts of the tree.
Lower branches should not be heavily shaded by branches higher up and some of them must be completely removed. A stub should be left while cutting back branches to the main stem so that re-growth of the moderately vigorous fruitful bud is encouraged. Avoid removing too many branches. When the main branches lose vigour these can be stimulated by pruning.
Harvesting and Handling of Apple Fruits:
The apple fruits should be harvested at proper picking maturity. It is a climacteric fruit. For distant markets, picking is done in advance to full maturity whereas for home markets properly ripe fruits are harvested. Picking of immature fruits results in poor quality with poor flavour and taste.
Such fruits shrivel during storage and are subjected to physiological disorders such as scald, bitter pit and soft core. The over mature fruits in some cases may develop soft scald and internal breakdown with poor shelf-life.
The time taken from full bloom to maturity is rather constant over a wide range of climatic and cultural conditions and is considered as one of the most reliable indexes of maturity. Red Delicious should be picked after 133-139 days after full bloom.
The cultivar Golden Delicious should be picked after 148-154 days, Royal Delicious after 115-120 days, Granny Smith after 176-182 days and Tydeman’s Worcester after 88-94 days. Change of the colour of fruits from green to yellowish green indicates that fruits are ready for harvesting. However, fruits of green variety are judged by taste. The flesh firmness can be determined by removing a thin slice of the skin and flesh with a knife and recording the pressure.
Most of the commercial varieties require the flesh firmness of 16-18 lb/sq. inch to give maximum picking maturity. Delicious group should be picked before it attains pressure of 15-16 lb/sq inch. By and large flesh firmness, change in good colour and total soluble solids should help to judge the picking maturity.
Method of Picking:
All the apple fruits do not ripen at a time on the tree and more than one picking are required. The apple fruits are harvested with great care. Careless handling by pickers, especially for fresh market can cause waste. Picking should start with the lower branches advancing to the top. Apple should be grasped in the palm of the hand and removed from the spur with a quick, upward twist of the wrist. A straight pull will usually result in pulling the stem out of the fruit or the spur from the tree.
Fruit stalk should remain with the harvested fruits. Harvested fruits are carefully placed in the container. Fruits are kept under the shade until they are picked up and prepared for their planned outlet. The yield of apple fruits varies greatly due to climatic conditions of locality, soil types, cultivars, management practices. A well grown apple tree yields 30-50 kg fruit per tree.
Sorting and Grading:
After harvesting, unwanted fruits are sorted out. The healthy fruits are cleaned by washing to remove dust and spray residue. Washing can be done with tap water or a dilute solution of 1 per cent hydrochloric acid to remove lead carbonate residues. Apple fruits are graded according to size and shape, colour and permissible skin blemishes.
They are graded into super, fancy, selected and commercial grades depending on market demands. For local market fruits are also graded into extra-large, large, medium, small, extra small and pittoo.
Generally, following proportion (%) of fruit size of different grades is found on a tree:
(i) Large, super and extra-large: 20-24%
(ii) Medium: 35-40%
(iii) Small: 15-20%
(iv) Extra small, pittoo and culls: 20-25%
Large, medium, small and extra small grade fruits are packed in four layers. The fruits of extra-large grade are packed in three layers. Pittoo grade fruits are packed with wrappers. The mechanical graders can be employed for quick and efficient grading of apple fruits.
The fruits should be properly packed to get premium in the market. Generally, the fruits are marketed after packing in gunny bags, wooden boxes, Tray packed wooden boxes (Table 1), Pine needle board boxes, Bamboo mat boards boxes, CFB cartons (Table 2) and plastic crates.
While wrapping fruits in papers, the paper is kept flat in one hand and the fruit is put at its centre with the calyx end downwards. The paper is then wrapped round the fruit in such a way that all the ends come over the stem. While placing fruits in the box, the stem end is put downwards and the calyx end upwards.
The size of the boxes is so adjusted for the different grades that in all cases the packed fruits will weigh 16-17 kg. The weight of box and other packing material is about 5 kg giving a gross weight of approximately 21-22 kg per box. While packing the fruits, the boxes are lined with newsprint to cover the bottom, sides and the top of the packed fruits.
The bottom and top of the box are also given extra padding with grass and pine needles to avoid spoilage during handling. Paper liners are given in the box and in between every two layers. Paper liners are also given between two rows lengthwise.
In order to get higher price and to make available apple fruits in off season their storage at low temperature is essential. The deterioration of apples starts after the climacteric stage. Quick removal of heat from the fruits is a pre-requisite for an effective storage. Pre-cooling is essential for Delicious apples, which otherwise show poor shelf life during August and September.
Cold storage and controlled atmospheric storage help to extend the market life of fruits. Apple fruits are stored in racks or in the wooden boxes (30 x 30 x 45 cm). The recommended storage temperature for most varieties is -0 to 1°C with 90-95% relative humidity and shelf life of fruits can be extended for 4-6 months.
In controlled atmospheric storage, carbon dioxide, oxygen, temperature and humidity are controlled in gas tight rooms. Generally, the level of carbon dioxide is increased to 2.5-3.0 per cent with a temperature of 30-32°F in controlled atmospheric storage. CA storage at 0-1°C in 2-5 per cent CO2 and -3 per cent oxygen prolongs the storage life of Golden Delicious, Mclntosh, Rome Beauty and Stayman Early Worcester cultivars for 8-9 months.
Pre-harvest spray of silver nitrate 100 ppm, sodium benzoate 500 ppm, benzothiodiazole 200 ppm proved effective in enhancing the overall quality of Starking Delicious apples both at harvest and after storage for 150 days at 0°C and 85-90% RH.
There are certain growth retardants that can help in increasing storage life of fruits while maintaining acceptable quality. The storage life of Red Delicious fruits prolongs with 1000 ppm CCC by a week. Post-harvest dipping of apple fruits with calcium chloride maintains higher quality and very less storage disorders.
Waxol at 8% in combination with Alar at 400 ppm for 40-60 seconds by dip method improve quality of Red Delicious fruits. This treatment inhibits respiration and pectin hydrolysis and reduces weight loss and organic acid content.
Colour Improvement and Enhancement of Ripening:
In general, buyers prefer red or yellow apples to green ones. Nearly all red colours in apples are due to soluble anthocyanin pigments. The red colour development in Delicious varieties is generally very poor in warmer and low lying apple growing areas below 1800 m above sea level. Application of ethephon at 500 ppm about 10 days before harvest improves the red colouration. Since ethephon accelerates the fruit abscission, naphthalene acetic acid at 10 ppm should be added to ethephon solution to check the abscission.
The maturity of fruits is over delayed at higher ranges i.e. above 2100 m and simultaneously the red pigment becomes too intense giving deep red to blackish appearance to fruits which become unacceptable to the consumers and give low returns. Under such conditions an application of ethephon at 1000 ppm in combination with 10 ppm NAA about 3 weeks before harvest enhances the ripening by 7-10 days and improves the colour of fruits in mid hills. The growth regulators should be sprayed separately and not to be mixed with nutrients, fungicides or insecticides.