How to influence onion bulb number

The number of onions produced is influenced mainly by 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 crop nutrition is important to help to reach yield potentials.


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.

Effect of nitrogen rate on onion bulb yield

Calcium Nitrate

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

Effect of nitrate source on onion yield


Potassium is important for high yields in onion crops.

Effect of potassium on onion yield

It is the second most utilised nutrient and uptake peaks during bulb formation and enlargement. However, care has to be taken as over-application can lead to yield reductions.