During cultivation, place mulch coverings around and between the plants to discourage weeds and to hold moisture in. Keep the soil moist so that shallow roots can take up water. Apply nitrogen fertilizers every few weeks to increase bulb size, and stop fertilization when onions start to push the soil away, and the bulbing process has begun. At harvest, the roots should be clipped and the tops should be cut back up to 3 cm. The bulbs should be allowed to dry for several weeks before being stored in a storage area. Store at 5 to 10°C in a nylon bag. In addition, do not store onions alongside with apples or pears.
The best soil for successful onion cultivation is deep, friable loam and alluvial soils with good drainage, moisture-holding capacity and sufficient organic matter. The optimum pH range, regardless of soil type, is 6.0 - 7.5, but onions can also be grown in mild alkaline soils. They require abundant sun and drainage. The onion plants grow well in raised beds or rows of mounded soils that are at least 10 cm high.
Onion is a temperate crop but can be grown under a wide range of climatic conditions such as temperate, tropical and subtropical climate. The best performance can be obtained in a mild weather without the extremes of cold and heat and excessive rainfall, however, onion can withstand freezing temperatures. It requires about 70% relative humidity for good growth. It can grow well in places where the average annual rainfall is 650-750 mm with good distribution during the monsoon period. Onion crops need lower temperature and shorter day light (photoperiod) for vegetative growth while during the bulb development and maturity stage it needs a higher temperature and longer day light.