Onions are one of the most important vegetables in any kitchen and are believed to have originated in west-central Asia. In Spain, some 35,000 hectares are cultivated, distributed throughout the provinces.
The regions where this crop is most widespread are: Levante, Centro and Andalucía. The total production of Spain is close to one million tons, and in international trade we are the second place as an exporter, behind the Netherlands. The preferred technique is sprinkler irrigation, although drip irrigation is increasingly used as a higher profitability is achieved.
Onions can be grown in various soils: deep and limestone and with alluvial sands or marly soils. Drip irrigation is very simple: you just have to place a drip hose more or less every two rows to get the most out of the system.
The same concept is applied for the suberigation, although the drip hose is placed at a depth of 20 or 25 centimeters to water the roots. Soil preparation is essential for irrigation to be effective. The distance of the uprigation hoses depends on the distance between the beds and the characteristics of the soil. This type of irrigation is used mainly when there are many plants or if the number of rows per bed is odd. The distance between the emitters and their capacity depends on the characteristics of the soil and the density of seeds, although they usually vary between 30 and 40 centimeters and 0.6 and 2 liters per hour.
Another important instrument for those who use drip irrigation is fertigation, which allows producers to assist crops efficiently. Keep in mind that the roots of onions are not very deep or fibrous, so fertigation must be very efficient. 50% of the total absorption of the three main nutrients (nitrogen, phosphorus and potassium) occurs during the last month before harvest, so we must try to fertilize when the plants really need it.