Role of Potassium in Onion Production

Potassium is involved in the production and transport of carbohydrates and sugars to the bulb; enzyme activation; and synthesis of proteins. It also maintains the ionic balance and water status within the plant, thereby improving resistance to cold injury and drought.

Potassium effect at growth stages

Stage Potassium effect
Pre-Planting Promote strong early growth
Vegetative Growth Ensure continued growth and development
Bulb Formation Peak requirements are during bulbing – for yield and quality
Bulb Fill Maximize dry matter & sugar accumulation as well as quality
See more on Onion Growth Stages.

General Guidelines for Potassium Application

Onions have a relatively high K-requirement. Maximum uptake is later than that of nitrogen and peaks during bulb formation and enlargement. However, over-application can lead to yield reductions.

Potassium Deficiencies in Onion

Leaf tips turn brown and there is some slight yellowing of older leaves. Growth slows and leaves become erect. The entire leaf may also droop, and appear thin and papery. Bulbs are soft with thin skins.