Bolting In Onion

By TheHindu on 16 Aug 2016 | read

Onion crop performance varies in different seasons or in different areas for the same seed and many times due to farmers’ unawareness. In many cases the defects are considered to be only due to seed, which is not always true.

Based on literature available on onion cultivation and as experienced by us in this region while working on this crop, the types of defects which are commonly seen are premature bolting, doubling or splitting of bulb at initial stages of crop growth as well as after bulb development. All these defects lead to economical losses to the growers.

Premature bolting

Early transplanting i.e. for rabi crop if done before middle of December there is more likelihood of premature bolting. Use of growth hormones for flower initiation may lead to premature bolting.

Farmers should take care to avoid above factors and also remove the premature bolters as soon as they are seen in the field to avoid contamination in adjoining fields as onion is a highly cross pollinated crop

Splitting of bulbs

Wider spacing, excessive use of fertilizers or delayed application of fertilizers i.e. after initiation of bulbing process, irrigation after prolonged dry spell, heavy irrigation at the time of maturity, injury to bulbs during weeding or insect attack, and delayed harvesting are some of the reasons attributed for this.

Planting schedule

Farmers should adopt the planting recommendation and fertilizers application practices properly.

Many times the splitting of bulbs after harvesting or in storage is noticed which is due to forcing of bulbs for more size by applying heavy fertilizers or growth promoting chemicals.

Proper spacing and fertilizer application is to be managed. As bulbing initiation is the effect of sunlight, when adequate sunlight is not available bulb initiation is hampered. It may lead to other defects such as pest or disease attacks.

Farmers should take care to see they do not use spurious fertilizers or heavy doses of growth enhancers during initial stage of crop growth.

(Dr. R. K. Singh, Assistant Director, email:, mob: 09881303443 and

Dr. R. P. Gupta, Director, National Horticultural Research and Development Foundation, Chitegaon, Nashik, Maharashtra, email:, mob: 9850880668.)