New seed-setting aggregatum variety

By Our Agriculture Correspondent

Scientists at the department of vegetable crops, Horticultural College and Research Institute (HC &RI), Tamil Nadu Agricultural University (TNAU), Coimbatore, have developed a new seed propagated aggregatum onion (small or country onion) variety. It has been recently released for commercial cultivation by TNAU as CO (On) 5-Onion.

This high yielding variety, with attractive pink and bold bulbs, is a free- flowering type with seed setting ability. It can be propagated through seeds as well as bulbs.

Any seed- setting onion variety, is preferred by the farmers over the bulb-propagated ones, as it would ensure a saving of up to Rs 1500 per hectare in the cost of seed bulb alone.

Developed through a mass pedigree selection from a local type collected in Gnanamedu village of Cuddalore district, this onion variety has a duration of 90 days.

For getting good setting, it should be grown in November to January season, and for harvesting bulbs it should be raised during March- July season. It has an average yield potential of 18.9 tonnes of bulbs per hectare, which is 18.8 per cent higher than that of CO 4. As seed crop, it takes 95-100 days, and produces 250-300 kg seeds per hectare.

Each clump of this variety produces three to five bulbs, which will weigh about 60 g. The bulbs have good flavour and taste. The variety is moderately susceptible to purple blotch disease, and it is a ready victim for thrips attack, according to the scientists. It can be grown in red loam to black soils with good drainage facilities and in areas with mild season without extremes of heat and cold.

The seeds are ideally sown in raised beds in February, and the seedlings are planted in the main field in March. A seed rate of 8 kg will be required to cover a hectare. The field should tilled well and thrown into ridges and furrows 45 cm apart.

The seedlings are planted on the sides of the ridges 10 cm apart. Irrigation should follow at weekly intervals, and as the crop approaches harvest, it should be reduced to an interval of ten days.

The variety does well under good nutrient management. Liberal quantities of ripe farmyard manure should be applied along with 30 kg nitrogen, 60 kg phosphorus and 30 kg potash per hectare as basal dressing.

Another dose of 30 kg nitrogen should be added on the 30 th day after planting. The crop has to be protected from thrips by using some botanical insecticides and by following other eco-friendly methods of integrated pest management.

The crop will be ready for harvest after three months of sowing. The bulbs should be cleaned and dried in shade for four days after the harvest.

The shelf-life of the onions can be increased by resorting to a spray of maleic hydrazide at 2500 ppm (parts per million) fifteen days ahead of the harvest, according to the scientists.

This variety has been found to be adapted to the fertile loamy belts in Coimbatore, Trichy, Pudukkottai, Nagapattinam, Thanjavur, Thiruvarur, Theni, Madurai, Namakkal, Cuddalore, Thiruvannamali, Thoothukkudi, Erode and Dharmapuri districts of Tamil Nadu under irrigated conditions.

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