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climate
apaya is basically a tropical plant. However, it also grows well in sub-tropical parts.
Low temperature and frost limit its cultivation in higher altitudes.
Excessively cold nights cause the fruits to mature slowly and to be of poor quality in winter season.
It can be grown from the sea level to an altitude of 1000 metres, but above an altitude of 600 metres, size and quality of fruits gradually decreases.
As it grows in sub-tropical and tropical climates, it can be cultivated in a temperature range of 25-35˚C.
In this region it can be grown successfully as a rainfed crop in areas with 1500-2000 mm of evenly distributed annual rainfall, though yield may be poor when compared to an irrigated crop, because winter drought restricts development of the plants and the fruits. High humidity affects the sweetness of the fruits.
Fruits tend to lose their sweetness in low temperature also.
A warm and dry climate is needed during ripening season. It can not withstand strong winds being a tender and shallow-rooted plant.
Soil: Papaya can grow in many types of soils, except sandy and sticky or heavy clay soils. Papaya roots are very sensitive to water logging or standing water. Even forty eight hour submergence can be fatal for the plant. In heavy soils, water accumulates during high rainfall, and diseases like foot-root and root-rot occur, which may cause the plantation to be wiped out in a short time. Hence a slightly sloppy land is preferred to a perfectly leveled one. Hilly soil of this region is best suited, being well drained in organic matter.
Propagation
apaya is invariably propagated by seed. For propagation, seeds are collected from ripe, large sized, healthy fruits, essentially from female plants free from pests and diseases. Sometimes, the seeds fail to germinate because seed viability is completely lost in about 45 days. The removal of a mucilaginous covering (sarcotesta) from the seed is helpful in more rapid and uniform germination than those seeds with their sarcotesta intact. Removal of sarcotesta is easily done by fermenting the seed in a bucket of water for two to three days. The sarcotesta breaks easily when the fermented seeds are mixed with wood ash and are rubbed gently in a piece of gunny cloth. The seeds are washed to remove exogenous material by putting them in another pot or vessel containing water. The viable seeds sink in water, while the nonviable ones, sarcotestas and other debris float and can be skimmed off. The seeds can be sown immediately, or they can be stored after drying in shade in airtight containers. The seeds, however, should never be dried in sun, as this leads to a total loss of their viability.
Nursery sowing should be done 2 to 2½ months prior to the scheduled date of transplanting in the field. Middle of February to middle of March is the best time for sowing the seeds in north eastern hill region, for transplanting in the beginning of monsoon. It is better to sow the seeds in perforated polythene bags, 22 cm x 15 cm, and 150 gauge thick. In case of heavy and medium soils, bags should be filled with a 1:1:1 mixture of FYM soil and sand. A potting mixture of one part soil and one part FYM is ideal for north eastern region, having a porous soil. Seeds should be treated with 1 percent agrosan G.N. as prevention against damping off disease. Two to three freshly extracted or stored seeds are sown in each bag at a depth of 1.5 cm. Light watering, with a watering can, should be done every evening except on rainy days. The seeds germinate within 2 to 3 weeks. Only one healthy seedling is retained per bag in case of Coorg honey dew and solo variety. About 250-300 g of seeds is enough to raise a sufficient number of seedlings for planting an area of one hectare. Top dressing of seedlings in bags containing urea or ammonium sulphate should be avoided, as this encourages damping off disease and development of tall and lanky seedlings which are less suitable for transplantation. The main objective of rearing the seedlings in a nursery is to obtain healthy (15 to 20 cm tall at transplanting stage) and stocky seedlings with a large number of fibrous roots and leaves. This is best achieved by using good quality farm manure for making potting mixture. Spraying of papaya seedlings with GA at 50 ppm, alar at 250 ppm and phosfon-D at 250 ppm increases the number of female flowers. Nowadays attempts are being made to propagate papaya by tissue culture from stem segments, roots, and leaf segments.
Transplanting
its 50 cm in size are dug at a spacing of 2 to 2.5 metres during the first part of May. The pits are exposed to sun for a fortnight and filled with top soil along with 20-25 kg of farm yard manure, 1 to 1.5 kg wood ash and 1 kg bone meal in the form of mounds. In absence of rainfall, water is added to the pots to settle down the mixture properly. Before transplantation, pits re drenched with eldrin to avoid termite attack. When the seedlings are 15 to 20 cm tall, the bag is cut open with a razor blade and the seedlings are transplanted in the pits in the evening.Usually three seedlings are transplanted about 15 cm apart in each pit. Watering is essential after transplantation for a quick recovery from the transplanting shock.
Manuring:A five month period from transplanting to first flowering is important for nutrition of papaya plants. The stem girth attained by a plant just before flowering decides the vigour and productivity of a plant. If the plant remains weak during this period owing to insufficient nutrition, production during the rest of its life is adversely affected. Therefore, fertilizers should be applied at frequent intervals and at proper rates for building a stout and vigorous plant before flowering, and to maintain its subsequent growth and productivity.
The importance of nitrogen, phosphorous and potassium for good growth and yield in papaya has been realized. A fertilizer dose of 400g nitrogen, 250g phosphorous and 400g of potassium per plant per year should be applied in six split applications under irrigated conditions, although in rainfed conditions, it can be given in two split doses; the first in the beginning of monsoon and second in the later part. If rainfall is well distributed from March to November, then it can be given in three split doses. Each plant should also be given 20-25 kg of farm yard manure once every year. At the time of fertilization, a sufficient amount of moisture is essential in the soil. The fertilizers should be well mixed in irrigation rings or basins by light digging or hoeing. Application of fertilizers should be stopped 6 months before harvesting the crop.
Interculture:The papaya plant grows very quickly and comes to fruit in a year’s time, so intercrops are not usually taken in papaya plantations. Papaya itself is commonly used as an intercrop in tree fruit orchards. Papaya is a shallow-rooted plant, which should never be given deep tillage. Only removal of weeds is required whenever desired. Papaya requires a constant supply of moisture for continuous growth and production, but it is not possible in the hills of this region. However, when there is a danger of frost injury, supply of moisture is useful.
Diseases and pests
Papaya has no serious insect, pests, but it has some serious diseases.
Collar-rot or Foot-rot
It is caused by a soil borne fungus Pythium aphanidermatum. In this region, the disease occurs at the base of the stems particularly during the rainy season. The fungus attacks the bark and causes swelling, cracking and rotting of stems and roots, especially in waterlogged conditions or in extremely moist, sticky soils. The terminal leaves drop, wilt, turn yellow and fall.
Control measures: It can be checked by spraying/drenching 6:6:50 Bordeaux mixture or (0.2%) esso fungicide thrice during season. It can be avoided if the plants are on a well drained land.
Root rot:It is caused by the fungus Rhizoctonia solani and Fusarium sp. in the nursery. In the later stages, this disease is caused by Phytophthora palmivora, mainly in the root system.
Control measures: Application of 100g of lime and 100g of copper sulphate in the pits is an effective preventive measure against this disease. Drenching with formaldehyde two weeks before sowing can give effective control in the nursery.
Damping off (Phytophthora sp) This fungus kills young seedlings in the nursery stage. This can be prevented by sterilization of the soil of nursery beds with formaldehyde, two weeks before sowing, or treating the seeds with agrosan G.N., captan or Ceresan.
Leaf-curl and mosaic (Papaya ring spot or papaya mosaic virus)
They are observed during rainy season when the vectors are most active and cause considerable damage. In leaf curl, leaves of the plants become crinkled and curled, the plants get stunted with small leaf size and do not grow further.
The mosaic disease starts as necrotic dots on the leaves. The lamina becomes yellowish green, malformed, upright and with blistered patches on it. Fruits are also affected.
Control measures: Practically there is no control measure for these viruses. The virus affected plants should be quickly destroyed to prevent the spread of these diseases. To check the insect vector, plants should be sprayed with 0.05 percent Malathion or metasystox at 10-12 days intervals.
Root knot nematode (Meloidogyne incognita)
Affected plant shows withering, yellowing and wilting. Knot like structures appear on the roots particularly under water logged conditions.
Control measures:This can be checked by use of nematicides (nemagan, nemphas, etc) in the field.
