- Topology: The land should be more or less flat and access to a source of water. Onion is a cool crop.
- Soil Type: The soil should be light and well drained fertile sandy loam non compacted soils, it should be free from aggressive weeds like couch grass and be also in full sun. Test the soil to determine your soil fertility.
- Soil PH: Red coach F1 performs better within a PH 5.8-6.8. If the PH is below 5 apply calctic lime at the rate recommended by your soil test results
- Seed Rate: 1 kg of Red coach F1 is enough for one acre-mix them with the same amount of sand then fill farrows evenly with seed-sand mix when sowing.
Important Attributes of Red Coach F1
- Early maturing variety; 80-90 days from transplanting
- It’s a mid-short day hybrid red bulb onion variety
- It’s flattened globe shape bulb onion
- Produces medium to large dark red bulbs
- Very vigorous plant with strong root system which makes it ideal for hot growing conditions
- Has firm bulbs with good storage ability of up to 3 months
- It’s a pink rot resistant variety which makes it ideal for most Kenyan soils
- It produces 25-30 tons of uniformly mature deep red bulbs
- Make raised beds in rainy seasons and sunken beds in dry seasons of 1 m width and of any desired length
- Apply well decomposed manure at the rate of 5kgs per square meter-mix and apply D.A.P at 0.5 kg per square meter
- Make shallow furrows of 15 cm apart and 1-2 cm deep
- Plant the seeds and cover lightly with the soil and apply mulch
NB: Ensure that your nursery is protected against fungal infections, Soil-borne pests and seed dormancy is worked on by embracing new nursery technology called PLO; which means a combination of three quality chemicals that controls soil-borne pests and diseases, P is Pyramid – a fungicide that controls soil-borne diseases such as damping off and downy mildew, L is Loyalty – an insecticide for control of soil-borne pests such as cutworms and O is Optimizer – a bio stimulant fertilizer that manages crop stress. Mix 50 gm of pyramid plus 10 gm of Loyalty and 20 ml of Optimizer all in 20 L of water and do soil drench in the nursery.
- After sowing, irrigate the nursery bed literally two times a day for 10 days and then continue watering regularly; every evening or morning, depending on the prevailing weather conditions.
- Germination takes about 7 days, remove mulch and erect the shade above the tender seedlings
- Transplant of seedlings takes 6-8 weeks after sowing when they have attained pencil thickness and 15 cm of height
- Transplant when seedlings have 3-5 well-formed leaves
- Two weeks before transplanting, reduce the shade to improve seedling survival rate in the field
NB: Spray Optimizer at a rate of 20 ml/20L of water three days before transplanting to minimize transplanting shock, Optimizer is a biostimulant & foliar fertilizer that manages crop stress, improves crop immunity and boosts the overall growth of onion crops.
Onions are spaced at 30 cm by 7-10 cm
Apply 3-5 tons of well-decomposed farm yard manure in an acre at the time of final land preparation
Apply 100 kg of N.P.K 17:17:17 when planting/transplanting, 60 kg of CAN as top dress (30 days after transplanting)-5 cm below the seedling and 2 cm to the sides gives the plant efficient use of fertilizer
Red coach F1 takes 3 months to full physiological maturity
Onions are ready to harvest when they form a shiny membranous cover around the bulbs or when the foliage withers. Harvest when rains are little or during dry season, Harvesting is done by pulling the bulbs carefully from the soil then chopping off the leaves or by bunching the onions together and hanging them up in an airy space for about a week until all the outer leaves are nicely dried then bulbs can be easily pulled from the bunches.
Don’t store freshly harvested bulbs on the floor, the floor increases humidity hence high rate of rotting. Put onions in loose bags/nets and store them in a well-constructed storage facility
Purple Blotch-Fungus- Alternaria Porri
This disease is found in all onion growing regions but is most virulent in hot, humid conditions.
Small, watery lesions with a white centre are formed on the leaves. As the lesions grow larger, brownish purple rings containing spores are formed. The edges of the flecks are reddish purple and these are ringed by a yellow zone. If the flecks merge with each other they can affect the entire leaf, causing it to snap and die. Older leaves are also the most vulnerable to this disease.
How it spreads
The fungus can remain in plant debris and waste heaps from where it can attack the plant. The spores are formed during damp nights and when leaves are wet for longer than 12 hours. When the leaf or leaf debris dries out, the spores are spread to other leaves via the air. The first symptoms become visible between 1 and 4 days after infection. The optimum temperature for this disease is 25º C when the bulbs are most vulnerable.
Apply extensive crop rotation. Ensure that the leaves don’t remain wet for long periods by having good drainage and by planting less densely. Avoid excessive irrigation. The weather conditions and the expected time that leaves will be wet must be taken into account.
White Rot – fungus-Sclerotium cepivorum
White rot is one of the most important and a destructive fungal disease of onions and it causes damage wherever onions are cultivated.
Leaves become yellow and wither. When an infected plant is uprooted a thick white fungal growth is seen on the roots and the bottom of the bulb. Innumerable small black sclerotia form in this fungal growth and on the affected parts.
White rot fungus can stay in the soil on plant debris or as sclerotia. The sclerotia can remain dormant in the soil for many years germinating as soon as onions or a related crop are cultivated on the land again. White rot can spread quickly from root to root. Cultivation machinery, planting material, crates or footwear can also spread the disease. White rot doesn’t cause a lot of damage in the first year of infection, but in the following years considerable numbers of plants may fail because the number of sclerotia can increase rapidly.
Managing white rot is complicated, as the sclerotia can survive in the soil for up to 20 years. Avoiding infection is essential. Follow good hygiene protocols on the farm. Avoid soil from infected plots being carried by machines to other plots. Correctly registering infected plots can prevent it from spreading to uninfected plots. Inspect the propagating material (for example onion sets) for the presence of white rot. If the disease is detected for the first time in a certain plot, remove and destroy as many infected plants as possible to prevent the rapid spread of the infection. Inundating or solarising infected areas or entire plots can reduce the number of sclerotia.
Bacterial Soft Rot; bacterial-Erwinia carotovora subsp.carotovora
Bacterial soft rot occurs in many types of vegetable crops. It can considerably reduce the yield of onion crops both in the field and in storage.
Erwinia can infect the plants in the field. The leaves wilt and will dry out at a later stage. If an infected plant is cut through, it can be seen that the middle of the new bulb is completely slimy and stinks. The scales are soft and appear watery.
Later on a pale yellow to light brown slime will form. Affected bulbs are soft and watery. When squeezed, the bulb oozes stinking fluid or slime.
The bacteria that cause problems when cultivating onions are only found in the soil, surface water and on crop debris. Infection almost always begins via wounds that have been caused by insect damage, hail, heavy rain and strong wind. There can be many sources of infection such as through the fungal infections, leaf rot and downy mildew, damage caused during growth or harvesting i.e. topping too early or too short.
Another source of entry can be when leaf axils begin to rot following prolonged rain. The bacteria mainly penetrate the bulb via wounds on the neck, but this is not always the case. Water is necessary for infection. The warmer it is the faster the infection progresses. The bacteria become inactive at temperatures lower than 3ºC.
Pink Root -Fungus-Pyrenochaeta Terrestris
Plants that are heavily infected with pink root look as if they are suffering from lack of water or as if they have a deficiency disorder. The roots of infected bulbs first become light pink in colour and depending on the extent of the infection the color becomes more intense changing from pink to red to deep purple. After this the roots shrivel up and die. Pink/purple discoloration are also seen on the skin of white onions.
The fungus remains in the soil in the form of dormant spores or in plant debris of one of its many host plants. Infection occurs when onion roots come into contact with the fungus. Because pink root doesn’t attack the bulbs base the plant continues to develop new roots which are then also infected. When plants are heavily infected there will be few or no healthy roots left, resulting in retarded growth and reduced yields. Pink root doesn’t continue in storage.
Only cultivate varieties that have a high resistance in infected fields.
Apply a 4 to 6 year crop rotation using resistant crops.
Downy Mildew – Fungus –Peronospora destructor
Downy mildew can be found in almost all the important onion growing regions. It occurs mainly during periods of cool, humid weather and affects the quality and quantity of harvests.
The initial symptoms to appear are pale green oval patches which in a later stage become covered with violet grey spores. Foliage that has been affected becomes more susceptible to other fungi such as Alternaria, which turns the foliage black.
The disease arises during humid weather conditions with the optimum temperature for its development being between 15 and 20º C. Early infection can cause considerable damage. If conditions for infection remain favorable fora prolonged period the disease can extend to infect large areas of the field. In the end, plants that have been infected will die prematurely leading to reduced harvests. Infected bulbs can lead to storage losses. The fungus can remain in the soil or survive on plant debris, waste heaps and in onion storage facilities. As well as this, overwintering onions and first year sets can often be sources of infection, the fungus spores are spread by raindrops and wind and they will germinate and infect the leaves under conditions of rain, dew and high humidity (RH>95%).Once the fungus is present in the plant it grows systemically and can then continue to produce spores.
Ensure that crop debris is ploughed well into the ground and cover waste heaps. Don’t irrigate excessively. Rotate crops every
3 or 4 years or longer.