Role of Zinc in Onion Production

Zinc is important for the development and function of growth regulators (e.g. auxin) that influence internode elongation. It is also involved in chloroplast development and thus important for photosynthesis.

Zinc effect at growth stages

Stage Zinc effect
Pre-Planting Ensure good shoot growth
Vegetative Growth Ensure photosynthetic growth is not limiting
Bulb Formation To maintain leaf growth
Bulb Fill Less critical, but to maintain growth and prolong bulking
See more on Onion Growth Stages.

General guidelines for Zinc application

Zinc uptake can be restricted by excessive use of phosphorus. Thus it is important that zinc and phosphorus are balanced, particularly during early stages of growth.

Zinc deficiencies in onion

Deficient plants are stunted and have twisted, outward bending leaves. Older leaves take on an orange mottled appearance. Younger leaves have a faint chlorosis and yellow striping. Bulbing can be delayed and crops may not store well. Problems are more common on high pH or calcareous soils or during cold, wet weather.