Influencing Onion Bulb Number

The number of onions produced can be influenced by a variety of factors, for example, plant density. Planting crops at higher densities can result in greater numbers of onion bulbs, but of smaller size. Thus, it is important to manipulate sowing density to provide maximum yields of a desired bulb size. A balanced fertilization program will help to reach yield potentials.

Crop Nutrition and Onion Number


Nitrogen is one of  the most important nutrients required for high onion yields. Onions are known as gross feeders and crops can remove 2-3 kg of nitrogen for every ton harvested.


Potassium is important for high yields in onion crops. It is the second most utilized nutrient and uptake peaks during bulb formation and enlargement. However, care has to be taken as over-application can lead to yield reductions.

Calcium nitrate

Studies with calcium nitrate confirm this is one of the most effective forms for high yields.


Trials have shown that zinc nutrition can improve seed germination and seed yield, both important for high yields.