How to Improve Onion Firmness

Firmness is a critical characteristic of onion crops, particularly in dry bulb onions which are stored for long periods.

Growers can influence bulb firmness by applying balanced nutrition.

Nitrogen influences onion firmness

Nitrogen plays an important role in bulb firmness. Potassium and calcium deficiencies can also lead to bulbs with lower densities.

Effect of nitrogen rate on onion firmness

Nitrogen can help to increase the specific weight of the outer skin, which results in an improvement of the bulb’s resistance to pressure, therefore reducing handling and storage damages. However, overall bulb firmness may decrease with high rates of nitrogen due to a softening of internal tissue.