Onion is a bulb. It is a vegetable which is most widely cultivated species. Its genus is Allium. This genus contains several other species also.
Onions are distributed across the world. These are served cooked as food item. However, these are also eaten as salad.
When cut onion irritates eyes due to some chemical substances in it.
Onion is cultivated for about 7000 years. The geographic origin of onion is uncertain. History reveals that onions were used as far back as 5000 B C. Ancient Egyptians respected onion bulb due to its concentric rings as symbol of eternal life.
Onions are cultivated in well drained fertile soils. Sandy loam soils are best suited for onions.
Onions grown in clayey soils are more pungent as they contain more sulphur. It needs more nutrients in the soil. Nitrogen, potassium, and phosphorus are needed in good quantity for onions.