Botanical Name: Allium cepa L.
The onion is one of the most important commercial vegetable crops grown in India: The demand for onion is worldwide. It is used both in raw and mature bulb stage as vegetable and spices. The pungency in onion is due to a volatile oil known as ally-proopyldisulphide. The bulb of onion consists of swollen bases of green foliage leaves and fleshy scales. Maharashtra, Tamil Nadu, A.P., Bihar and Punjab are the important onion producing states.
Onion is a cool season crop. It is grown during winter and harvested before the real hot season begins. Onion can be grown under a wide range of climatic condition. But it succeeds best in mild season without extremes of heat and cold. According to Rao and Purewal (1954), it can be grown as a rained crop even at elevation of 1500 to 2000 m between April and August, Onion produce bulbs more rapidly at warm (210C to 260C) that at cool 150C to 210C) temperature.
Onion can be grown on various soils. But sandy loam, silly loam and deep friable soils are best suited for onion crop. The land is prepared by giving 5-6 ploughings. The optimum pH range is between 5.8 and 6.5.
SEED RATE AND TIME OF SOWING
In onion 10 to 12 kg seeds require/ha..For kharif it is sown in June & for rabi sown in October-November.
LAYOUT AND SPACING
Ridges & furrow type of layout is follow15x10 cm. spacing is given. In case of onion preferably flat beds are use because
- As in flat beds plants accommodate are more than ridges & furrow so we get more yield.
- In flat bed (leveled) there is equal distribution of water & fertilizers. So we get uniform size & compact bulb of onion which have good keeping quality in storage & transport.
- In percentage of twines is less in flat beds than ridges & furrow.
25 to 30 cart loads of well rotten FYM or compost applied at the time soil preparation per hectare. For onion 50 kg N, 25 kg P^Os & 25 kg Potash should be applied, as .usual method.
Cultural Operation keeps the field absolutely free from weeds to produce a good crop of onion. Weeds if not controlled in early stage but removed later on, will injure the onion bulbs and the out-turn will be poor. 2-3 hoeing and weedings are enough for the crop. After 2 to 3 irrigations, earth up the poor plants. According to Mehta (1959), if the mature bulbs are to be stored for any length of time care should be taken to cut away the seed stalks as soon as they come out, otherwise they will develop thickness will not be cured properly and, therefore,, they will also fail to keep well in storage. Though no work has been done on the usefulness of crushing or bending over the leaf tops to hasten maturity yet the results of experiments done in U.S.A. indicate that it is an ineffective measure.
The root system of onion is restricted io top 8 cm and roots penetrate seldom deeper than 15 cm. Water requirement of the crop at the Initial growth period is less. Irrigation should be stopped 15-20 days before attaining maturity for improving the keeping quality of bulbs. Frequent irrigation delays maturity. In kharif season, depending upon the rains and time of planting 6-10 irrigations are enough. In rabi, 10-15 irrigations are given at bulb formation, irrigation is necessary and moisture stress at this stage results in low yield.
HARVESTING AND YIELD
Follow harvesting of onion bulbs at right stage of maturity. It is important in deciding storage life of onion as bulbs may be stored for about six months. The onion bulbs, reach maturity when the plants cease to produce new leaves and roots. In onion, neck fall is the indication of maturity. Time of harvesting depends on several factors tike planting season, cultivar, market price and condition of the crop. In general, when about 50 percent neck fall is seen crop is harvested. Onion for storage should be fully developed. Thick-neck bulbs which result due to premature harvesting do not store well. Late harvesting leads to increased respiration, subsequent susceptibility to diseases and excessive sprouting during prolonged storage and left in field sunburn is also noticed. Bulbs are harvested by hand pulling if soil is light; they are also harvested by hand implements. Kharif crop, since the growth continues forced toppling should be taken up to stop growth 15 days before harvesting. Onion along with tops are kept in field for 2-3 days, curing for 3-4 days is necessary to remove excess moisture from outer skin and neck to reduce shrinkage and development of colour in storage. In rabi season, yield of onion is around 25-30 tons per hectare, while in kharif season it is comparatively low. Yield : In onion we get 150 to 250 quintals of yield/ha
Pusa red, Niphad-404, Ni-207-1, Ni-2-4-l(Ail red), Ni-5-7-1 (white), Pusa Ratnar, Early Guano. Onion (Allium cepa)
Recommended by the Department of Agriculture, M.S. during 1990 and also released at the National level by All India Coordinated Vegetable Improvement Project in 1987. Suitable for kharif season in western and northern India. Duration is 90-100 days. Bulbs are medium, flatish round and red in colour. Average yield is 250 quintals per hectare. (MPKV, Rahuri)
Developed by selection, improvement over N-53 suitable for kharif season and released in 1986. Bulbs are globose in shape with crimson red colour with 13 % TSS. Duration is 10.0-110 days. It has less bolting ability compared to N-53. Average yield is 250 quintals per hectare. (MPKY, Rahuri)
Developed during early sixties for rabi season by the Department of Agriculture, M.S. and recommended at the National level by AH India Coordinated Vegetable Improvement Project in 1985 for Tones IV and VII of India. Bulbs globose in shape with brick red colour, TSS 12-13 per cent. Average yield is 300-350 quintals per hectare. (MPKV, Rahuri)
It was developed by selection from local material. It was released at MPKV, Rahuri in 1984. Duration is 120 days. Suitable for rabi season. Bulbs are globose in shape with white colour. Average yield is 250 quintals per hectare. (MPKV, Rahuri).
Developed by selection from local germplasm collected from village Kegal of District Kolhapur and released in 1994. Bulbs are globular in shape with white colour. TSS is. 13 per cent. Suitable for dehydration. Average yield is 250 – 300 quintals per hectare.(MPKV, Rahuri).
It is useful for round the year plantation. Yellow coloured variety suitable for export to Europe, Australia and America. Pungency mild, TSS 11.5 per cent and excellent keeping quality (4-6 months). Suitable for both the rangada and rabi seasons. Yields about 240 quintals per hectare. Besides it is released through the State Variety Release Committee of Maharashtra it is also notified by the Central Sub Committee on Crop Standards, Notification and Varietal Release at the national level. (MPKV Rahuri).
1) Onion Thrips: This is surplus in onion. It is a small sucking insect that feed on leaves and lacerate tissue.
Control Measures: This pest can be controlled by spraying the crop with Dimethoate (Rogor-30 EC) or Methyl Parathion (Metacid – 50 EC) or Oxydemiton methyl (Metasytox – 25 EC) @ I ml per liter of water.
2) Lear Eating Caterpillar: This caterpillar is occasionally found cutting the leaves damage the crop. Control Measures: Spraying the crop with Lindatie 20 EC or Methyl Parathion (S) 1 ml per liter of water can control this pest. Diseases Management in Onion 1) Blight: Altenariapilanduiiand A.porri Small white sunken lessions with purple centre appears on leves and they enlarge rapidly, girdling the leaves and flower stem which fall over and the bulb decay follows in the storage.
Control Measures: This disease can be controlled by spraying the crop with one per cent Bordeaux mixture or Mancozeb (Dithane M-45) @. 2.5 gm per liter of water or Copper Oxychloride (Blitox-5Q) @ 5.0 mg per liter of water.
3) Onion Smut: Uracystis cepulae Frost. Dark, slightly thickened area appears on cotyledon of young seedlings with numerous raised blisters near base of scales of older plants, which on rupturing expose black and powdery mass of spores.
Control Measures: The disease can be controlled by seed treatment with Thiram @ 45 gm for 0.45 kg of seed (Larson and Walker, 1953) .and spraying formaldehyde solution in the furrow.
4) Base Rot: Fusariwn oxyspomtn Schtecttt. It is due to this disease that yellowing and drying back from the tip of leaves occurs. The serial parts of the disease affected plants may die in one or two weeks or decay may extent over a much longer time.
- Crop rotation with plants not affected by this fungus may help to control this disease.
- Spraying the crop with Mancozeb (Dithane M-45) @ 2.5 gm per liter of water may reduce the incidence of this disease.