Onion : Harvesting
Onion is harvested depending upon the purpose for which the crop is planted. 0nion crop is ready for harvesting in five months for dry onion. However, for marketing as green onion, the crop becomes ready in three months after transplanting.When the bulbs developing from the leaf bases of onions are fully formed, the leafy green tops begin to yellow and eventually collapse at a point a little above the top of the bulb, leaving an upright short neck. When the tops "go down" in this way, the bulbs are ready for harvesting. Because all the onions in a crop do not mature at the same time, large-scale commercial growers harvest them when about half the tops have gone down.
In kharif season, since tops do not fall, bulbs are harvested soon after the colour of leaves changes to slightly yellow and red pigmentation on bulbs develop. Best time to harvest rabi onion is one week after 50% tops have fallen over. Onions for sale as dried bulbs or for storage should be harvested progressively after tops have started falling over.
Since onion bulbs are normally formed at the soil surface, it is sometimes possible in sandy soils to pull the mature bulbs by hand. Where conditions make hand pulling impossible, crop is harvested by loosening the bulbs with a fork or hoe before lifting them. The harvested crop is left in windrows in the field for a few days until the tops are dry. The windrows should be made so that the green tops cover the bulbs to protect them from unburn. The leaves are cut leaving about 2-2.5 cm tops above the bulb after complete drying. This practice helps to increase the dry matter content. If tops are cut too close, the neck does not close well and provides entry for decay organisms. Early harvest results in sprouting of the bulbs and late harvest results in formation of secondary roots during storage. In kharif season, late harvesting results in doubles and bolting.
Yield
Irrigated onion crop in rabi season gives an yield of 25-30 t/ha while under rainfed conditions it yields only about 0.7-1.0 t/ha. Onion raised as an intercrop in sugarcane and turmeric, in alleys of young fruit garden and banana garden, gives a yield of 5-9 t/ha. The small sized, pungent, local cluster type onion yields half as compared to the large sized varieties.