- Onion primarily uses nitrogen. If nitrogen is in excess, especially during the second half of the vegetation period, the development of bulbs is delayed and their storage during winter may be jeopardized.
- During the rooting phase, onions consume phosphorus, nitrogen, and calcium. Onions need nitrogen during the period of growth of the vegetative mass. The need for potassium increases during the period between the formation of the bulb and ripening.
- Phosphorus should be applied uniformly during the growing season.
- Sulphur is necessary for the conversion of nitrogen compounds to proteins. A sufficient number of fertilizers containing sulphur increase the transportable qualities of onion and the duration of storage.
