Onion Growth Stages: Learn and Grow
Role of nutrients by onion growth stage
TRANSPLANTING
Nitrogen and Potassium – promote strong early growth
Phosphorus – maximize root development and to supply reserves for season long growth and good bulbing
Sulfur – encourage plant growth
Boron, Manganese and Zinc – ensure good shoot growth
Vegetative Growth
Nitrogen and Potassium – ensure continued growth and development
Calcium, Sulfur and Magnesium – maintain vigorous, healthy leaf growth and to build plant supplies prior to bulbing
Micronutrients – ensure photosynthetic growth is not limiting
Bulb Formation
Nitrogen – in nitrate forms to maintain bulb development and early growth
Potassium – peak requirements are during bulbing – for yield and quality
Calcium – ensure good supply to the bulb to maximize eventual storage quality
Micronutrients – to maintain leaf growth
Bulb Fill
Nitrogen – in reduced amounts so as to maintain dry matter production but not compromise bulb quality
Phosphorus – encourage ripening, early maturity and a big bulb size
Potassium – maximize dry matter & sugar accumulation as well as quality
Calcium – maintain good bulb firmness and quality with reduced storage problems
Sulfur – depending upon the desired pungency of the onion
Boron – to improve storage quality and calcium uptake
Copper – for good skin quality. Other Micronutrients – less critical, but to maintain growth and prolong bulking
