An onion (Allium cepa L.), also known as the bulb onion or common onion – is a popular vegetable of considerable economic importance. The species belongs to the amaryllis family, genus – Allium. The onion’s shape, size, and color are varietal characteristics.
Onion development is closely related to the length of the day and the amount of light reaching the plants, i.e. – onion bulbs only form at a certain length of day.
Considering this feature, the distinguishing features are:
- long-day varieties – forming thickenings begin onion bulb formation when the day length is 15–16 hours
- short- or intermediate-day varieties – form thickenings begin onion bulb formation when the day length is 12–14 hours.
The plants form leaves from the moment of sowing until the occurrence of a certain day length. When the day reaches this length – formation of the bulbs begins.
Depending on the length of the growing season, it is considered to be divided into varieties:
- early (80–100 days)
- medium-early (100–130 days)
- medium-late and late (more than 120 days)
This feature defines the period that plants need to reach maturity naturally, and thus produce a maximum yield of properly grown onions.
Three methods of growing onions are used: from seeds, from seedlings, from onion sets.
GROWN FROM SEEDS
Growing from spring sowing is the dominant method in Poland for producing onions for storage. Onions are among the plants that have a fairly long seed germination period (11–25 days, depending on sowing date and weather conditions). It is important to sow the seeds as early as possible so that by the time the long day arrives, the plants will have produced the large vegetative mass necessary to produce a high yield of onions. At the same time, it is necessary to take into account the risk of a recurrence of spring chills, which result in poor and uneven emergence. On the other hand, sowing too late results in delayed ripening, the production of finer bulbs, as well as a higher proportion in the yield of bulbous and thick-necked onions. For sowing, use only healthy seeds with a high seed value and a germination rate of more than 85%.
It is recommended to treat seeds with the microbial product PRIMSEED® BIOM HORTI, which is very beneficial for the growth and initial development of young plants.
Onions respond very positively to organic fertilization. It also requires intensive and rational mineral fertilization, adapted to the needs and abundance of the soil, determined by soil analysis.
Apart from basic soil fertilization, foliar fertilization is a standard. Its main advantage is the quick and effective supply of the most-required nutrients to plants at particular stages of development.
- Applied after emergence, activator of plant rooting ROOTSTAR® provides zinc, in the form of ammonium zinc acetate, stimulates the formation of auxins, i.e. it is one of the precursors for auxins, especially indoleacetic acid (IAA).
- Phosphorus, delivered by foliar application during the development of the first leaves, has a beneficial effect on the rate of development and growth of the assimilative leaves. It also supports the development of the root system (GROWON® or PLONVIT® FOSTAR or PLONVIT® PHOSPHO).
- During intensive growth of assimilative leaves, it is especially important to have an optimal supply of nitrogen (PLONVIT® NITROMAG or PLONVIT® NITRO). Well-formed assimilative leaves are a strong guarantee of a high onion yield.
- From the beginning of the formation of the onion bulb, very important is potassium, which is responsible for production and transport of photosynthetic substances to the harvestable plant parts. Also, it regulates water management of plants and sugar biosynthesis (PLONVIT® KALPRIM, PLONVIT® KALI).
- In the fertilization of onions, magnesium should be taken into account (MIKROKOMPLEX®), as well as sulfur (PLONVIT® SULVIT), especially when a nitrate-urea solution is used to fertilize the plants with nitrogen.
- The most important of the micronutrients are: zinc (AMINO ULTRA® Zn-24 or MIKROCHELAT Zn-15) and manganese (AMINO ULTRA® Mn-22 or MIKROCHELAT Mn-13), as well as copper ( AMINO ULTRA® Cu 24 or MIKROCHELAT Cu-15) and molybdenum (MIKROVIT® MOLYBDENUM).
- For ensure large yield quantity and good quality – biostimulation is very important. The foliar applications of TYTANIT®, OPTYSIL®, AMINOPRIM®, VANADOO®, PLANTICINE® may stimulate plants for better growth and yield and for improvement of tolerance to abiotic (weather conditions) and biotic (disease and pest appearance) stresses, as well as the capability of accelerating the recovery of plants after the occurrence of stressful conditions.
- Particularly noteworthy are the highly alkaline line of fertilizers ALKALIN: ALKALIN™ K+Si, ALKALIN™ KB+Si, ALKALIN™ PK 10:20. Alkaline pH of fertilizer solutions activates the immune factors of plants.
- During sowing worth to apply BACTIM® TERRASTART. This is a fertilizer that ensures optimal distribution of nutrients thanks to microgranular formulation. High phosphorus content and the innovative SAFE-P formula, have a positive effect on the development of the root system. In addition, the product also contains easily absorbable zinc, which is essential for the initial development of plants.
- It is important to reduce nematodes in onion crops. For this purpose, the use of BACTIM® RECEPTOR is recommended. It is a bioproduct especially advisable for sites threatened by nematodes. This product can be used prophylactically as a single dose or several times depending on the pressure of nematodes. On nematode-free sites, it is worth using BACTIM® VIGOR. This product positively affects the size and quality of the crop. It reduces the susceptibility of plants to abiotic and biotic stresses.
INTERMAG’s wide range of products, allows you to develop your own individual foliar fertilization and biostimulation program, considering local soil conditions, crop intensity, stage of plant development and availability of various products.