A long-day onion hybrid with mid-late maturity. When direct seeded in the open field, produces bulbs within a single crop season.
A very early-maturing intermediate-day onion hybrid. When direct seeded in the open field, produces bulbs within a single crop season.
A new long-day onion hybrid with mid-early maturity. Matures 118–120 days after sowing.
Botanical and biological features
The onion (Allium cepa L.) is a plant belonging to the Alliaceae family of the order Liliales. It is a biennial plant which forms a bulb(s) during the first year and seeds during the second year.
Onion is a cold-resistant plant. Germination occurs at 3–4˚С. The optimum germination temperature is 18–20˚С. Seedlings withstand a temperature drop down to 2–3˚С below zero without being injured. The optimum temperature for leaf formation and growth is 18–24˚С. At temperatures below 10–15˚С, no bulbs are formed, and bulb growth is arrested at temperatures higher than 30˚С.
The onion plant is characterized by relatively low water consumption. At the same time, onion has high requirements for soil and air humidity. This is due to the fact that its root system is poorly developed and shallow. At different stages of development, onion has not the same soil moisture requirements. Soil moisture content should be high during germination and bulb formation and low during bulb maturation.
Onion can grow on almost any type of soil with good aeration. The best preceding crops are fallow, winter cereals, grain legumes, early potato, and cucumber. Thorough soil cultivation in autumn is vital for onions. They can be sown (direct seeded with small black seeds), planted as small bulbs (onion sets), or transplanted. The sowing (with small black seeds) is normally performed as early as possible in spring, at the first opportunity to go out to the field. In home gardens, the recommended seeding rate is 6–10 g per 10 m2. At 1–2 true leaves, the plants are thinned out to a distance of 4–5 cm between plants. When sowing with the aid of a precision seed planter, the seeding rate is 4–5 kg/ha. The depth of seeding is 1,5–3,0 cm, depending on the soil type and growing conditions. The distance between rows is 25–30 cm.
To obtain a yield of 10 kg/m2 (100 ton/ha), fertilizers should be applied during basic soil preparation at a rate of 750 g of nitroammophoska per 10 m2 (N 120, P2O5 120, K2O 120 kg of active substance per hectare). During the growing season, supplemental fertilizer applications are made on a regular basis with a total application rate of 250 g of ammonium nitrate and 300 g of potassium nitrate per 10 m2 (N 125, K2O 135 kg of active substance per hectare), with most of the potassium nitrate to be applied 3 to 4 weeks prior to bulb maturity thus improving onion storability. The final rate of fertilizer application is calculated based on the soil nutrient status data.
During the growing season, onion should be given 8–12 irrigations with the water application rate of 350–400 l per 10 m2 (350–400 m3/ha) per irrigation. With onions grown for storage, irrigation is discontinued 3 weeks prior to harvest, otherwise the bulbs will have poor storage ability. Combining drip irrigation with application of water-soluble fertilizers through the drip irrigation system (fertigation) is a highly efficient technique resulting in a more uniform moisture and fertilizer distribution in the root zone, more efficient water use, less soil compaction, and no soil crust formed. Readily soluble mineral fertilizers are given with each water application.
The major pests are the onion fly and thrips. Control measures: deep autumn cultivation of soil, strict adherence to the crop sequence, applying two insecticide sprays every 10–12 days during the flight of onion fly (second half of April – early May). Such treatments are also effective against other insect pests (leek moth, bulb fly, weevil). Thrips attack the crop throughout the growing season. Control measures: sprays with insecticides such as Sumi-Alpha, Karate, Zolone, Basudin, Fastac, etc.
Downy mildew is the most damaging disease.
Control measures: adherence to the crop sequence, good cultural practices, regular (every 10–14 days) treatments with fungicides such as Aliett, Acrobat MC, Ridomil MC, Quadris, Copper Oxychloride, etc. To prevent causal agents from developing resistance to the chemicals applied, it is necessary to alternate fungicides having different active substances in their formulations. For the preparations to stick to the foliage more efficiently, adhesives (Trend, Silvet, skimmed milk, or household soap in the amount of 30–50 g per 10 l of water) are admixed into the spray solution, otherwise drops of the spray solution falling on the waxy surface of the onion leaf will tend to roll off, dramatically reducing the efficiency of treatment.
For an earlier harvest (2 to 3 weeks earlier than usual), onion is cultivated by transplanting. The sowing takes place 55–60 days before transplanting in the open field. The transplants should have 3–4 well-developed true leaves. The recommended temperature conditions for growing onion seedlings are as follows:
- prior to emergence: 20-25˚C;
- following emergence, for 3 to 4 days: 10-12˚C in the daytime and 8-10˚C at night;
- subsequently: 18-20˚C on sunny days, 14-16˚C on cloudy days and 12-14˚C at night.
About 10 to 12 days before transplanting, hardening of seedlings (transplants) should be started by opening the tunnel cover almost completely. Hardening of seedlings is an obligatory agricultural method in cultivation of onions.
Harvesting of onions normally starts when 70% of leaves have lodged. By the time of harvest, the plant density should be 50–60 pl/m2 (500,000–600,000 pl/ha) for salad varieties (Candy F1, Exacta F1, Sierra Blanca F1, and Sterling F1) and 60–80 pl/m2 (600,000–800,000 pl/ha) for storage varieties (Teton F1, Pinnacle F1 and others).
Onion is highly sensitive to day length. Therefore, it is vital not to be late with sowing and to grow varieties and hybrids previously tested and approved for cultivation in your growing area. Growing hybrids not adapted to this particular growing area can result in a considerable drop in yield. Other possible abnormalities include premature bulb formation at poorly developed foliage (when growing short-day varieties in areas with extremely long days) and, conversely, bulbs may not reach maturity or even may not be formed at all (when growing long-day varieties in areas with extremely short days).