ABSTRACT
Onions are grown universally and constitute an important part of the diet for people in virtually every country. Onions are of worldwide importance since countries in Asia, Europe, North America, and South America are listed among the major producers. Onions may serve as a staple or as a condiment in the diet, depending upon culinary use and ethnic origin. Temperature and daylength are the most critical environmental factors in onion production. Onions can be grown successfully on soils ranging from light, sandy loams to organic soils. Numerous interacting conditions influence onion yield, for example variety, plant population, daylength, temperature, water, and availability of essential elements. Improved onion varieties and hybrids are made available to farmers by government agencies and the seed industry. Onions planted and grown when temperatures are near the lower limit of growth may require additional N fertilization since the mineralization of organic soil N is restricted at low soil temperatures.
