Things farmers ignore when growing onions

Friday November 02 2018
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Two women prepare onions for the market in this photo taken in September in a farm in Kilongoni, Makueni County. A good onion harvest offers 20-25 tonnes per acre depending with the variety. PHOTO | PIUS MAUNDU | NMG


Last week, I received a call from Lucy, who is considering to venture into onion farming.

Lucy was very particular, as she wanted tips on growing the crop to get higher yields since she has seen there is huge demand in the market.

As an agronomist, we get such requests all the time and Lucy’s was no different. I wrote to her on email this comprehensive guide that I regularly discuss with farmers.

“There two major types of onions grown in the country, namely spring and bulb, with the latter having a longer shelf-life.

Prices of onions fluctuate from as low as Sh40 per kilo at farm gate to Sh80 per kilo depending on the season and variety planted.

The price fluctuation is also mainly attributed to the importation of onions from Tanzania, where the cost production is lower.”


However, farmers like Lucy who are based in Nairobi should know the best timing is between November to May as onions fetch high prices.

“The best areas suited for growing onions are Kajiado, Karatina, Oloitoktok, Kakamega, and Naivasha, among others.

Onions do well in well-drained fertile soils rich in humus with the pH ranging from 5.8-6.5

The common varieties grown in Kenya include Jambar F1, Islero, Red creole, Red Passion and Red Pinnoy.

All the varieties in Kenya prefer warm to hot temperatures, that is 15-30 degrees Celsius.

An acre requires 1-1.5kg of onion seeds depending on the variety and the spacing. The spacing normally affects the size of the bulb onions.

Onions can be grown by direct seeding, which requires intensive management or one can decide to first establish a nursery bed

Just like other vegetables planted on nursery bed, site selection is key to proper planning for production of healthy and vigorous growing seedlings. The site should be in a secure environment, near a water source and preferably near the crop production site.

It should be raised to a height of about 15cm to encourage drainage, 1m width for easy workability and the length of your own desire depending on the number of seeds to be sowed.

Shallow drills are made 2cm deep and 15cm apart after levelling and seeds sowed singly. This is achieved by mixing sand and onion seeds in a ratio of 3:1.

Cover the nursery bed using agro — nets or dry grass free of weeds, pest and diseases and immediately after sowing, watering should be done twice per week depending with the moisture level. In most cases, the seeds sprout after seven days.

The crop in the nursery should be established for 4-6 weeks and transplanted when pencil size in thickness, 10 to 15cm tall and have 3-5 true leaves.


It’s always wise to do a soil test before planting to know the status of nutrients in the soil, which will guide you on nutrient application for onions production.

A serious farmer should prepare the land to a fine tilth and add well decomposed manure. Depending on the soil test, one can consider using DAP during planting and top-dress using CAN at week four. Frequent scouting for crop nutrition is paramount and mitigation measures should be taken immediately.

To prevent the transplanting shock, do the exercise early morning, late in evening or when the weather is cloudy.

It’s ideal to trim the shoot and root (3 inches for shoots and 0.5 inch for roots) before seedling placement to minimise moisture loss and seedling shock during and after transplanting.

The ideal spacing is 8-10cm between the seedlings and 15cm for inter row distance to allow better bulb development. Spacing is also determined by the variety planted and soil fertility.

Onion production can be done in the greenhouse and open field depending on the location with the latter being more preferred.

Pests and disease

Pests such as thrips, onion flies, red spider mites and diseases such as downy mildew, purple blotch and rust affect onions. Frequent scouting for pest and diseases is important for early detection, prevention and control.

The land should be free of weeds, which compete for nutrients, light and space and harbour pest and diseases. This is done by mechanical methods or the recommended herbicides.


Once transplanting is done, one should prepare to harvest after 4-5 months depending on the variety. Top leaves will yellow and begin to fall over, an indication they are ready for harvesting, which should coincide with dry and hot weather.

Curing of the onions is done by uprooting every single stem and leaving it to dry after which leaves and roots are cut off with a sharp knife. A good harvest offers 20-25 tonnes per acre depending with the variety. Lucy wrote back to me saying she had made up her mind to farm onions. I will give progress on how she is fairing.