An apple tree loaded with fruits
An apple tree loaded with fruits
is the most important temperate fruit of the northwestern Himalayan
region in India. It is predominantly grown in
The apple-growing areas in India do not fall in the temperate zone of the world but the prevailing temperate climate of the region is primarily due to snow covered Himalayan ranges and high altitude which helps meet the chilling requirement during winter season extending from mid-December to mid-March.
CLIMATE AND SOIL
Most of the apple varieties require 1,000-1,500
hours of chilling below 7 C during winter to break the rest period.
These conditions are available at an elevation of 1,500-2,700 m above
mean sea-level in the
Well distributed rainfall of 100-125 cm throughout the growing
season is most favourable for its optimal growth and fruitfulness. The
long drought spells during fruit development and excessive rains and
foggy conditions at fruit maturity hamper fruit size and fruit quality.
Dry temperate areas suitable for apple cultivation in Himachal Pradesh
Soil depth, drainage and pH determine the suitability of soil types. Loamy soils, rich in organic matter having a pH of 5.5-6.5 with gentle to moderate slope, proper drainage and good aeration are most suitable. The soil should be free from hard substrata and waterlogged conditions. Where cultivation is done on flat soils, proper drainage channels need to be developed to restrict the incidence of collar rot, root-rot and other soil-borne diseases.
Apple varieties should have climatic adaptability, attractive fruit size, shape, colour,
Table1. Recommended varieties of apple in different Indian states
good-dessert quality, long shelf-life, resistance
to diseases and pest and tolerance to drought conditions besides high
productivity. In fifties, the
green English Varieties-McIntosh, Baldwin, Jonathan, Cox’s Orange
Pippin, Golden Delicious, Black Ben Davis and Pippins-predominated. Of
late, the coloured Delicious, group now occupies more than 83% of the
total areas under apple in Himachal Pradesh, 45% in
Table2. High-colouring and early and early-maturing sorts of apple.
Recently, a further shift form Delicious group to improved spur types and standard colour mutants has been observed. The spur-type mutants produce trees 50-80% of the standard size with 20-50% higher yield potential in addition to early fruit maturity and better fruit colour. The, colour mutants produce standard sized trees with early and better fruit colouration. Some of the promising high colouring and early sports of Delicious group identified for cultivation are listed in Table2.
The high-yielding apple Scarlet Gala and Red Fuzi have also been introduced in Himachal Pradesh and hills of Uttar Pradesh. These are being evaluated on size controlling clonal rootstocks M 9, M 26, M 7, MM 106 and MM111.
A number of scab-resistant cultivars have been introduced
since the incidence of apple scab in epidemic form in 1972-73 in
Hybridization programme of apple resulted in release of Lal Ambri (Red Delicious x Ambri) and Sunehari (Ambri x Golden Delicious) in Jammu and Kashmir; Chaubattia Princess and Chaubattia Anupam (Early Shan burry x Red Delicious) in Uttar Pradesh hills; and Ambred (Red Delicious x Ambrich (Richared x Ambri) and Ambroyal (Starking Delicious x Ambri) in Himachal Pradesh. Ambrich, Ambroyal and Ambred have not gained popularity among the growers of Himachal Pradesh because of very late maturity and extended harvesting period, whereas high-colouring and early-maturing cultivars are preferred.
These varieties perform well in areas where winter chilling is less than 800hr below 7 C, insufficient for breaking dormancy of Delicious varieties. Introduction of low-chilling varieties has expanded the scope of apple cultivation to warmer and marginal areas. However, all low-chilling varieties are poor in dessert quality, subacid in taste and have poor shelf-life and as such have a scope for commercialization. Important table-purpose, low-chilling varieties are Michal, Schlomit, Anna, Tamma, Vered and Neomi. Tropical Beauty and parlin’s Beauty are suitable for processing purposes.
The most important feature of a pollinizing variety is that its flowering should synchronize with the main variety. In addition to this, it should have abundant viable pollen, long duration of flowering, compatibility with main variety, self-fruitfulness, regular bearing besides good commercial value. The Delicious group of varieties are self-incompatible and cross-pollinated, whereas most of the English varieties are self-pollination and act as suitable pollenizer for Delicious group of varieties in the proper proportion of 11-30% in main variety plantation depending on the situation of the orchard. The most suitable pollinizzing cultivars are Tydeman’s Early, Red Gold, Golden Delicious, McIntosh, Lord Lambourne, Winter Banana, Granny smith, Stark spur Golden Spur. A combination of early, mid-season and late-flowering pollinizers provides assured cross-pollination for the main variety. A combination of Tydeman’s Early, Red Gold and Golden Delicious has been recommended in Himachal Pradesh for Starking Delicious plantations. The flowering crabs have varieties are Red Flush, Crimson Gold, yellow Drop, Manchurian, Snowdrift, Golden Hornet and Malus Floribunda. Red free and Liberty, resistant to scab, can also be used as pollinizers.
PROPAGATION AND ROOTSOCKS
The apple plantations are raised on seeding rootstocks. The used of clonal root stocks has not been commercialized despite the established superiority for raising uniform plantations, precocity and high productivity in Himachal Pradesh, Jammu and Kashmir and Uttar Pradesh. Non-availability of clonal material in the absence of commercial mass propagation techniques has remained the major constraint. Apples are propagation on seedlings of crab apple or self-pollinizing varieties, Golden Delicious, McIntosh, Yellows Newton and Northern Spy having good seed viability, germ inability and seedling growth. The seeds of commercial varieties from fruit juice canning units are also used by nurserymen for raising seedling stocks. However, the seedling stocks lack uniformity in tree size and productivity but show better adaptability to sloppy and shallow soils under rain fed conditions.
Apple seeds need stratification in moist sand at 4 -7 C for 60-90 days. The water-soaked seeds are placed between 2 and 3 cm thick layers of moist sand in wooden boxes or polythene bags during December. The stratification boxes or bags are placed in cool place where the required chilling temperature of less than 7 C for 1,000-1,500 hr is met in 60-90 days. The sand is kept moist during stratification. The stratification can be accomplished in the lower chamber of the refrigerator also. The stratification requirement is also met with in areas having very cool winters by direct sowing of seeds in nursery beds during November-December. The pre-stratified seeds, as indicated by whitish tip at the micropylar end, are sown during February-March in well-developed, raised beds. Sowing is done in rows 10 cm apart with the spacing of 5 cm between the seeds and 2-3 cm deep. Nursery beds should be irrigated after sowing and covering with 10 cm hay or pine needle mulch to protect the germinating seedling from heavy rains and spring frost. Mulch when the seedlings are 5 cm long for the straight upright growth of seedlings. One-year-old seedling stocks are ready for grafting during February-March.
Table3. Clonal rootstock for apple
The size controlling Malling (M) and Malling Merton (MM) series clonal rootstocks were introduced at the Regional Horticultural Research Station Mashobra and Temperate Fruit Research Station, Kotkhai, in Himachal Pradesh, Government Hill Fruit Research Station, and Chaubattia in Uttar Pradesh and Fruit Research Station, Shalimar in Jammu and Kashmir during late sixties.
The size-controlling clonal rootstock of apple is mound layering (stooling). The rooted layers of the clone are planted in well-prepared stool beds during winter at a distance of 30 cm in the row and 60 cm apart. The 3-4 years old layers give rise to numerous suckers during spring. The suckers are covered with the soil before monsoon. The suckers are ringed or notched near the base during the rainy season and covered with soil to encourage rooting. The difficult-to-propagate rootstocks like M 9 need the treatment of 1,000-2,000 ppm IBA at the notched portion for quick root initiation. The rooted layers are separated t the onset of dormancy (December) and lined out in nursery beds for further grafting with scion varieties during February-March. The rootstock should be healthy and disease-free and should attain the thickness of 0.9-1.25 cm at grafting eight for proper bud-take success. The growth of the rootstock should be straight and upright with proper root development. There should be no gall, knot or injury scar at the grafting height.
The rootstocks of apple are grafted with desirable scion variety during February-March. The scion wood should be collected fro, the mother plants of known pedigree. It should be collected from bearing trees only. One-year-old shoot growth is ideal for scion wood. Scion sticks should have only vegetative buds and not the reproductive buds. The scion wood should be healthy and disease-free. They should have 3-5 well-developed buds with smooth internodes. These should be collected during dormancy.
The scion wood collected prior to grafting must be properly stored. It should be kept slightly moist and at a low temperature to prevent the bud-break. A common method is to wrap the wood, in bundles of 25-100 sticks, in polythene sheets or bags. Moist saw-duct. Wood shavings or moss should be used for packing to maintain moisture during storage. Sand should be avoided as it sticks to the scion wood and blunts the edge of knife during grafting. The storage temperature is also very important. If the scion wood is stored for 2-3 weeks, 5 C storage temperatures is satisfactory. However, If the scions are to be stored for a longer duration (1-3) months), the scion wood should be kept at about 0 C to keep the buds dormant Scions cannot be used for grafting in the active stage of growth.
Tongue grafting is the ideal method of grafting scion cultivar on the rootstock with more than 90% bud0take success. The scion should be grafted 15-20 cm above the ground level. February-March is most suitable time of tongue grafting. It should be just before the bud-break. In tongue grafting, a slant cut is made on the rootstock 2-3 cm ling across the stem about 15-20 cm above the crown. A vertical cut is given from one-third of the top of slant cut and extended up to two-thirds of the length of slant cut. Similar cuts are made on the scion wood and the 2 parts are connected by inner locking the tongues made by vertical cuts on scion and stock. The cambium of the 2 portions should match for successful graft. The graft union is wrapped with polythene wrapping should be removed.
“T” budding during monsoon and chip budding during August can also be done for propagating scions with good bud-take success and smooth scion-stock union but the plant growth is poor in the Indian conditions. It takes one year for raising grafted plants, whereas two in case of budded plants of standard size.
Before planting an apple orchard, proper decisions should be made on selection of varieties, rootstocks, tree size, spacing, placement of pollenizer and planting layout. The planting distance varies according to variety, vigor of rootstock, fertility of soil and climatic conditions. In flat and valley areas, the planting is done in square or hexagonal system of layout. However on slopes, contour or terrace planting is preferred. The usual pit size is 1 m x 1 m x 1 m without any hard pan or rock at its base or on the sides. The pit should be dug and filled up one month before planting. The top soil and sub-soil should be piled separately while digging. Top soil must be filled first followed by sub-soil on the top to improve the fertility of lower layer of pit. While pit filling, 40-50 kg well-rotten farmyard manure and 500g of super phosphate should be mixed in soil. The soil is allowed to settle for one month before planting. An early planting of apple in December-January is desirable for proper establishment. Graft union should be kept 25 cm above the ground level to avoid collar-rot and scion rooting
The combination of rootstock and scion variety determines the planting distance and planting density. In standard plantations, the plants of standard varieties grafted on seedling stocks are planted at a distance o f6-7.5 m, accommodating180-250 plants/ha. The planting distance can he reduce according to the vigour of rootstock? The clonal rootstocks particularly dwarfing and semi-dwarfing root stock should be used where the soils are flat, fertile and irrigated.
High-density planting has consistently increased in popularity and acreage particularly with small land-holding in the Indian conditions recently. The traditional systems of planting having long juvenile period are labour-intensive and low-yielding with poor-quality fruits, whereas high-density planting is more efficient orcharding system. It is precocious, easily manageable, has higher yield potential, with better quality fruits and higher returns/unit area. The high-density planting cannot be adopted in very steep, unfertile, shallow and drought-prone areas.
There are 4 categories of high-density planting-low (less than 250 plants/ ha, moderate (250-500 plats/ ha), high (500-1,250 plants/ha) and ultra high density (more than 1,250 Plants/ha). With the increase in planting density, the yield may increase, but beyond a threshold bensity, quality is deteriorated and may not be profitable in terms of economical returns. Super high-density plantings or meadow orcharding with a density of 20.000-70,000 plants/ha in some European countries have been raised but not commercialized so far. The major advantages of high-density planting are:
. Potential of precocious
. Low labour costs and better orchard management
. Improved fruit quality
The trees of high-density plating should have maximum number of fruiting branches and minimum number of structural branches. The branches on the tree should be so development that each branch casts a minimum amount of shade on other braches. To develop favourable characteristics,, following rules must be followed.
. Prevent upright growth o tree
. Develop horizontal branches
. Space small laterals, along the central leader
. Develop and maintain fruiting spurs along the entire branch as it develops
. Develop rigid, strong, self-supporting laterals
. Develop fruiting spurs along the sides rather than top or bottom of lateral branches.
Tree size control
A key to successful high-density planting depends upon control of tree size Following tree size controlling methods can be adopted to develop high-density plantings.
. Use of size-controlling rootstocks
. Use of spur-type scions
. Training and pruning methods to induce dwarfing and spreading habit or tree
. Mechanical devices like branch bending to control size
. Use of chemicals
The most convenient and indispensable method of tree size control in apple high-density planting is the use of size controlling clonal rootstocks. The combination of rootstock and scion variety determines the plat spacing and planting density/unit area. The recommended planting density and spacing are given in Table 4.
Table4. Spacing and planting density for different scion-stock combination
The plants are trained according to growth habit and vigour of the rootstocks. Training helps to establish a strong framework of scaffold limbs capable of supporting heavy yield with quality fruits, regulate annual succession of crops, expose maximum leaf surface to the sun, and direct the growth of the trees so that various cultural operations like spraying and harvesting become economical, protect the trees from sun-burn and promote early production. The training procedures for standard and dwarf plants differ.
The standard trees are trained on modified central leader system. The ideal standard tree can be trained as:
Pruning in apple is essential to maintain a proper balance between vegetative growths and spur development. The basic steps of pruning standard bearing trees are:
Precautions in pruning
Application of manures and fertilizers start right from planting of orchard. The First application should be made at the time of filling of pits. The fertilizer dose depends upon the soil fertility, type of soil, kind and age of trees, cultural practices, climate and crop load. The dose of manures and fertilizers should be determined on the basis of soil and leaf analysis.
In an orchard of optimal fertility, N, P and K may be applied in the ratio of 70:35:70/ year age of the tree. The dose should be stabilized (700:350:700 g N: P: K/ tree) after 10 year of age. These applications may be supplemented with farmyard manure @ 10 kg/years age of the tree with the maximum of 100kg. Apple trees prefer N, P and K in the form of calcium ammonium nitrate, super phosphate and muriate of potash respectively. As the crop load is low in an ‘off’ year, the standard fertilizer dose of NPK may be reduced to 500g, 250g and 400g respectively. Since the response to P application is poor in P-rich acidic hilly soils, it would be a better practice if P is applied after every 2-3 years or should be reduce to half annually in such conditions.
In bearing trees, farmyard manure along with P and K should be applied during December-January. Nitrogen is applied during February-March, 2-3 weeks before bud-break. The N can be given in two split doses, first 2-3 weeks before bud-break and second one month after flowering, where the irrigation facilities are available. The fertilizers should be broadcast in the tree basins 30 cm away from tree trunk to the canopy drip line and mixed well in the soil. Deep cultivation to mix the fertilizer in soil should be avoided, as this practice injures root system.
Table5. Nutrients deficiency symptoms and corrective measures
In high-rainfall areas with steep slopes and small basins band application of N is preferred.
There are deficiencies of macro as well as micronutrients. The B, Zn, Mn, Ca and N have been found in deficient range mostly and symptoms can be easily identified on leaves or shoots. The symptoms and corrective measures of important nutrient deficiencies are given in Table 5.
Clean basin management is the common practice of floor management
in apple. The basins are kept clean by hand working, hay mulching or
black alkathene mulching. In cool climates, black alkathene mulch is
very efficient which not only controls weeds and conserves moisture but
also improves the fruit quality. It should be avoided in warmer areas,
as black alkathene absorbs the solar heat and increases the soil
temperature, hampering root growth. Application of Glyphosate @ 800ml/
ha or Grammaxone/Paraquat (0.5%) as post-emergence herbicide suppresses
the weed growth for 4-5 month. In the initial years of plantations,
green-manuring crops like sunflower and bean may be cultivated between
the basins to improve the soil. Improved grasses like orchard grass
(Dactyl is glomerata), tall fescue (Fescue arundinaceae) and timothy (Phleum
pretense) and nitrogen-fixing legumes like red clover (Trifolium repens)
Heavy bearing in apple usually results in small-sized, poor-quality fruits and sets in alternate bearing cycle. Judicious fruits thinning at proper stage of fruit development not only regulate cropping but also fruits size and quality. The practice is essential in pollinizing. Carbaryl or Sevin @ 750-1,000ppm or NAA @ 10-20 ppm at petal fall results in optimal fruit thinning. Hand-thinning can also be done but it is very cumbersome and uneconomical procedure.
Most of commercial varieties experience 3 phases of fruit drop-early drop, June drop and preharvest drop. The early drop considered natural, occurs due to lack of pollination and fruit competition. The June drop is caused by moisture stress and environmental conditions which can be checked by maintaining soil moisture through irrigation or mulching. The preharvest drop cause serious economic losses, as the mature marketable fruits abscise before harvesting due reduction in level of auxinus or increase in ethylene levels in fruit. Early-ripening varieties like Tydeman’s Early, Red Gold and Pippins experience 40-60% drop, whereas in Delicious group loss occurs to the extent of 15-20% of crop load. Application of NAA (10 ppm) before the expected fruit drop or 20-25 days before harvesting checks the preharvest fruit drop effectively.
Most of apple orchards in India are situated in rain fed sloppy areas where irrigation facilities are inadequate except in flat valley areas. Apple requires uniform distribution of rainfall throughout the year or needs to be supplemented with irrigation during critical periods. The most critical period of water requirement in apple is from April to August, the peak requirement being after fruit set. In areas where irrigation is available, apple requires about 114 cm water during the whole year which can be scheduled in 15-20 irrigations. In critical summer months, the irrigations can be given at 7-10 days interval and rest at 3-4 weeks interval. At least 8 irrigation during critical period of water requirement are recommended for Starking Delicious apple. With the introduction of drip irrigation system, irrigation can be extended to scarce water source areas and hilly slopes also. About 1,695 litres of water/tree is required during the season in drip irrigation compared with 3,840 litres/tree in the conventional method of irrigation. In drought-prone and water-scarce areas, the soil moisture can be retained by hay mulching or black alkathene mulching immediately after spring rains.
HARVESTING AND POSTHARVEST MANAGEMENT
Since apple is climacteric fruit, the maturity of fruits does not coincide with ripening. The fruits usually do not attain fully ripe edible quality on the tree while harvesting. The fruits should be harvested at proper picking maturity to attain proper edible quality at ripening. Picking of immature fruits results in poor quality fruits lacking flavour and taste which shrivel during storage. Over-mature fruits develop soft scald and internal breakdown with poor shelf-life. There are several maturity indices which can be adopted in proper fruit harvesting. The TSS of fruit pulp, ease in separation of fruit from spur, change in ground surface colour from green to pale, change in seed colour to light brown, fruit firmness and days from full bloom to harvest are some reliable maturity indices for apple which can be considered singly or in combination.
All the fruits do not mature evenly on trees depending on the time and number of flower flushes. Thus more than one picking are required. Apple fruits should be picked in such a way that bruising and stem punctures are avoided and pedicel must remain with fruit. Apple should be grasped between index finger, middle finger and thumb, and quick upward twist of wrist will easily pluck the fruit along with pedicel. Picked fruit should be placed softly in the picking bags or baskets. The fruits should be transferred carefully from picking baskets to boxes or baskets be transported to packing houses for grading and pacing.
After picking, the fruits should be placed in a cool and ventilated place to remove field heat before packing. Air cooler, cold water sprinkling or fruits washing with water also helps quick removal of field heat. Keeping fruits over-night near the tree basins for cooling down is another practical way to remove field heat. Fruit surface must he free of moisture before grading, wrapping or packing in cartons.
Apples are graded according to fruit size and fruit
appearance or quality. On the basis of fruit size, apples are graded
manually in 6 grades. On the basis of fruit colour, shape, quality and
appearance, apple fruits can be graded in 3 or more quality grades.
These grades are designated as AAA, AA and A; A, B, C; or extra fancy,
fancy class I and fancy class II. For size grading, mechanical graders
with washing and waxing facilities are available in
Apples are packed in wooden boxes. Size of wooden
boxes used in different apple-growing areas of
Corrugated-fibre board (CFB) cartons are also available for packing apples. Such cartons are of 2 types-universal cartons and telescopic tray-pack cartons. The CFB cartons not only save the precious wood and forest wealth but result in very less fruit bruising (3.5%) which fetch good market price. The usual dimensions of CFB cartons with trays are 50.4 cm x 30.3 cm x 28.2 cm (outer jacket) and 50.0 cm x 30.0cm x 28.2 cm (inner case).
Apples have a longer storage life compared to other fruits. However, different varieties have different storability. Deterioration of fruits starts after climacteric stage. However, shelf-life of apples can be prolonged by prolonged by providing optimal storage conditions. The cold storage retards fruit deterioration and reduces decay from pathogens and shrivelling from water loss. The recommended storage temperature for apple is -1.1 -0 C which is about 0.8 -1.8 C above the average freezing pint of most apple varieties. The relative humidity of 85-90% should be maintained in cold storages. Most apple varieties can be stored for 4-8 month after harvesting Ambri has the longest storage life.
Scald is one of the storage disorders in apple.
Light mottling on greener surface of fruits are initial symptoms of
scald. Darkening become more severe with elapsed time and ultimately
extends to red surface also. Scald usually affects the skin only but in
sever cases it may extend to fruit flesh. The immature fruits are most
susceptible to scald which is aggravated by warmer temperatures in
Bitter pit is characterized by small sunken spots on the fruit surface which are more prevalent near the blossom-end. Initially small water-soaked areas appear which shrink and turn brown with the loss of water and ultimately become brown localized areas of the dead tissue. Unlike the name, these corky tissues are never bitter in taste. The immature picked fruits and large-sized fruits in ‘off’ year are most affected, Golden Delicious, Yellow Newton and Graven stein being most susceptible apple varieties.
Internal browning is associated with apple Yellow Newton and is characterized by brownish streaks radiating into flesh from the core. Controlled atmospheric storage with higher temperature can be helpful to control this disorder. Appearance of disorder is less at 1 C in cold storage.
Dr. R.P. Awasthi and Dr. P.S. Chauhan