An onion (Allium cepa L.), also known as the bulb onion or common onion – is a popular vegetable of considerable economic importance. The onion’s shape, size, and color are varietal characteristics. Three methods of growing onions are used: from seeds, from seedlings, from onion sets.
GROWN FROM ONION SETS
An onion set is a small onion that is used to produce a large commercial one. The entire cycle of grown from onion sets – takes two years. The harvest of the onion crop is at least 2–3 weeks earlier than onions from sowing.
- In the first year of grown, small onions called onion sets are obtained from seeds.
When growing onion sets, the soil should have a good structure, but should not contain too many nutrients so that the growth and overgrowth of the bulbs does not occur too luxuriantly. In addition, the growth of set onion plants is limited by sowing a large number of seeds per unit area. Plants growing in density compete with each other for water and nutrients, developing small bulbs (up to 25 mm in diameter). Under conditions of limited nutrients and high plant density, onions grown as onions set finish growing more than a month earlier than consumable onions from sowing. A visible symptom of the maturity of the onions set is the breaking, yellowing and drying of the assimilative leaves.
Commercially approved onion sets are calibrated by horizontal diameter. There are four grades:
5–10 mm (fine)
11–15 mm (medium)
16–20 mm (partially large)
21–25 mm (large).
The most valuable are the onion sets with a diameter of 16–20 mm, useful for the production of onions harvested at different stages of growth. The smallest onion sets (5–10 mm) are suitable for the production of onions with shriveled up bulbs, but their maturity date is similar to that of cultivation from sowing. Bulbs with a diameter of more than 25 mm are intended for consumption.
2. In the second season, the onion sets are planted into the ground, where they continue their vegetative development.
The onion sets are planted in the field in spring, as early as possible, as soon as weather conditions permit. The field for planting onion sets is prepared similarly to that for onions from sowing. Nutrient requirements are also similar. Large onion sets (20–25 mm) can also be planted in autumn, but there is always a risk of frost and damage to the bulbs. Onion sets are most often grown for early bunching or with cut assimilative leaves, but also for trading with dry scaly leaves in summer and autumn.
From emergence until the appearance of the day length specified for the type of onion, the plants form leaves. This stage of development is very important, because it affects the later yield and its quality. Throughout the growing season, all crop treatments, including foliar treatments, should be carried out to ensure the best possible conditions for plant 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.
- 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.
