Introduction

Index

1. Introduction

          1.1 Overview

          1.2 Onion economy

1.1 Overview

Onion (Allium cepa L. , member of the Liliaceae family) is a herbaceous bulbous plant that is cultivated for bulb production either as biannual or perennial (depending on the cultivation conditions). It is probably originated in the mountainous regions of Central Asia. Onions are among the most widely adapted vegetable crops, and they can be grown from the tropics to subarctic regions. World production is nearly 85 million tons of bulbs on some 4.4 million ha.

The onion crop thrives in mild climates, with no extreme temperatures and without excessive rainfall. The optimum mean daily temperature for growing onions varies between 15 and 20°C. Under normal conditions onion forms a bulb in the first season of growth and flowers in the second season. The production of the bulb is regulated by day length. The critical day length varies from 11 to 16 hours, depending on variety. For the initial growth period, cool weather and adequate water is advantageous for proper establishment, whereas during ripening, warm, dry weather promotes high yield of good quality.

Onions can be grown on many soils but medium textured soils are preferred. Optimum pH is in the range of 6 to 7. Fertilizer requirements are normally 60 to 100 kg/ha N, 25 to 45 kg/ha P and 45 to 80 kg/ha K.

1.2 Onion economy

Onion growing areas

Onion trade (WTO 2014 data)