In addition to the vitamins it contains, the richness of the onion with mineral substances and other nutritious substances, especially the immune system strengthening feature, increases the consumption of onion day by day, which is reflected in the production. Day length and temperature are two important factors limiting onion growing. Cool air is needed in the early development phase of the plant. However, the Temperature must be high for the head bonding and the growth of the head. The average temperature in the early development phase should be 13 ºC.