Climate
- It is grown best where the climate is mild without the extreme heat or cold or excessive rainfall.
- Mild climate without extreme of high or low temperature.
- At early stage, plant can tolerate frost.
- temp for seed germination 20-25oC.
- Low temp and short photoperiod are required for vegetative growth, relatively higher temp and long photoperiod for bulb development.
- Lower temperature (1 – 21oC) and short photoperiod promote vegetative growth while higher temp. (15 – 25oC) and long photoperiod promotes bulb development.
- Opt temp for veget growth is 13oC-21oC and bulb devt opt temp is 15oC-250
- Adjusting planting time, can be grown from Terai to High Hill
- Onions start bulb formation when the day length is of the proper duration and different varieties of onions require different day lengths to initiate bulbing.
- High temperatures and low humidity are advantageous during bulbing and curing.
Soil
- It can be grown on various types of soil, but it grows best in light soil which may be sandy loam or silty loam.
- Heavy or clay soil should be avoided as they do not permit proper bulb development.
- Deep, friable sandy loam soil with high OM is best
- It is sensitive to acidity or alkalinity . pH 5.8-6.5 .