The onion (Allium cepa) is a biennial herbaceous plant that belongs to the Amarylidaceae family. It is the most widely cultivated species of the Allium genus. This edible bulb vegetable possesses a root system formed by numerous fascicular rootlets that originate in a stalk from which the leaves bloom. The numerous thick and fleshy layers in its interior save the plant’s nutritious substances. Both the bulb and the leaves are edible.

Nutritional characteristics

Composed of 91% water, 7% carbohydrates and 1% proteins, the onion is a bulb vegetable that contains a great amount of minerals and calcium, magnesium, chlorine, cobalt, iron and potassium, among others. It also provides large amounts of vitamins A, B1, C and E (antioxidant). Due to its ability to fight against microbes, bacteria and fungi, it is an excellent vegetable antiseptic.

Origin

Since prehistoric times, the onion has been grown and is edible. It is believed that the plant originated in Central Asia. Its domestication took place several millennia ago and evidence has been found of its consumption in Egypt 3,000 BC. It is also known that the Greeks and Romans ate onion it during the peak of their respective empires. By the Middle Ages, the onion and other legumes and sprouts were the main vegetables in the kitchens of both the poor and the rich. The onion arrived in America during Columbus’s second voyage and also during the voyages of the North American pilgrims.

Cultivation requirements

It is a mild, non-humid climate plant, although in the initial phases of cultivation it tolerates cooler temperatures. However, some varieties require warmer temperatures and longer days for the formation and ripening of the bulb. The onion prefers loose, healthy, deep soils, rich in organic matter, of medium, non-chalky consistency. Valley alluviums and the transported soils in the dunes close to the ocean are very suitable. It is also very sensitive to humidity since abrupt changes can cause the bulbs to crack. During its initial phase it demands humidity, but once the plants have begun to grow the soil’s humidity must be concentrated above 60% of the available water in the soil’s first 40 centimeters. In our country, the best yields are obtained with temperatures between 20 and 25 degrees Celsius, good light and low humidity. Its best yields are obtained with a soil pH between 6.0 and 7.0.

Varieties

There are numerous varieties of onions and they present bulbs of various shapes and colors. There are intense purplish red- colored onions, with a strong flavor; also yellow, white and pink with a milder flavor. They can be classified according to different characteristics. For example, we have the phytogeographic and ecological criteria. Also based on color and the shape of the bulb; mode of proliferation; commercial criteria, among others. The first approach is the only one that can be considered scientific and at the same time practical, because it involves the study of the ideal climatic and ecological conditions of the different varieties. This is of great importance in the acclimatization of the best species. Generally, the varieties are selected depending on their uses. The onion is used as a condiment, for seasoning, salads, pickling, and other purposes.

Onion planting and production in the Dominican Republic

The onion is the vegetable most used to condiment our food and it has become a very important crop for the Dominican economy. Approximately 94% is consumed fresh and 5% is used as raw material by industry for the production of seasonings, while a small amount is exported during some years. In our country, over 50% of onion production is traditionally concentrated in the South, primarily in Peravia and San Cristobal. Other areas include the valley of San Juan, Montecristi, San Jose de Ocoa and Constanza, although production potential exists in many other regions. Cultivation is carried out in zones that have guaranteed irrigation, where gravity-based irrigation and, to a lesser extent, pressurized irrigation are implemented. The following are the main varieties that have been cultivated for more than 15 years: Red Creole, Texas Early Grano-502 with red bulbs, the Yellow Granex F1 Hybrid, the Tropicana and the F1 Hybrid with yellow bulbs, all of which are short-day crops so that cultivation takes place exclusively during winter months.