The traditional onion planting season in Zambia for commercial hybrids is between the end of February and the end of March, although we do see earlier and later plantings.
To provide context, short-day onions (planted in Zambia) require 10 – 12 hours of daylight to form bulbs. Long-day onions require 14 – 15 hours of daylight to form bulbs and are not produced in Zambia.
With our normal rainy season, January tends to have the heaviest rainfall so planting early in January runs two risks: heavy rains washing away the fine onion seed and/or damaging seed beds, and overcast conditions that are not ideal for early growth of onions.
The heavy rains tend to ease off in March and less-cloudy days mean more sunlight, and farmers typically have better access to their fields for land preparation, so this is a more favourable time to plant.
Most short-day onions take 90 – 135 days to mature from emergence, although this depends on many factors. These include, but are not limited to, the sowing date, production location and seasonal variations (photoperiod and temperature). Further south, the days to maturity reduce as day length increases.
After onions reach maturity, their leaves “fall”. Lack of water could also cause onion leaves to fall and commercial onion growers often cut the water when they feel the onion is close to ready – perhaps it has reached the size required for the specific market.
Following this, onions are either harvested and sold as fresh onions, or they are cured and dried for storage. Curing usually takes between 2 – 4 weeks, depending on the conditions, and can be done in the field. This can be risky for onions planted later in the season, owing to warmer conditions Zambia begins to experience in September/October. Most farmers would cure their onions in a shed or onion bins. Once cured, to extend the storage, the ideal solution would be to cool the onions in a refrigeration unit.
Without this refrigeration option, onions can be stored for two to five months, although for each month of storage, the farm needs to account for post-harvest losses owing to a natural ongoing drying process, reducing the harvest weight, and also any damaged onions that might rot and potentially spread damage.
The size of the onions is largely determined by the plant population. While most seed suppliers recommend a plant population of 600,000 – 700,000 seeds per hectare, this is to achieve optimum yield potential with larger onions. With any onion production there is always a mixture of sizes in the field. Plant population guides the farmer in terms of what the bulk of his production should look like in terms of size.
In Zambia, we need to understand what the market requires. While formal retailers are an important market, the bigger markets for Zambian onions are local markets and the massive export market. These markets require smaller onions that store and travel well. To produce this smaller bulb size, seeding rates need to be increased. Up to 1.8 million seeds per hectare are planted, though the average is closer to 1.2 million seeds per hectare.
To illustrate the impact of seeding rates on size, see the table below. These figures are based on feedback from commercial growers.
In order to achieve this precision planting, a good quality fine seed planter is required. This is a specialised piece of equipment and is out of the reach of many of our small-scale farmers. These fine seed planters could be used for planting carrot seeds, too, as they are also very fine, but there is an even more limited market for carrots in Zambia, so this becomes a significant investment to consider.
Comparing ourselves with South Africa provides additional context. South Africa has a more formal supply chain – major retail players supply significantly more of the overall market. They look for large and medium-sized onions and have no market for the small onions that our market focuses on. These small onions are difficult to sell in South Africa; Zambia has the opposite challenge.
This immediately creates a significant distortion in the market in terms of supply-and-demand principles. Nearly all onion production in South Africa is from hybrid seed, giving the best opportunity for quality. In Zambia it is estimated that only 5 – 10% of our onion production is from hybrid seed.
In South Africa onions are grown from the northern borders to the far south. This means that it is possible to harvest onions somewhere in the country between June and January. Effective transport facilities mean the product can be moved from production areas to markets easily, if at high cost.
The intermediate varieties grown in the Cape generally have good storage capability and are largely used to supply markets between February and June, at which point the northern areas begin deliveries. This geographical diversity means that cold storage facilities are not essential for most producers. For Zambia to supply onions year round, such facilities would be needed, leading to increased costs.
What can we do as a country to improve our onion production?
We regularly have a shortage of good quality onions from April to June, and this is normal based on our growing cycles. We have three choices to fix this:
- Accept a lower quality of onion during this period.
- Invest in cold storage to extend the storage lifespan of the previous season’s onion production.
- Allow exports into the country for this period.
Some more practical advice would be to:
- Make more use of hybrid onions. This is proven worldwide as the best single solution to low yields and poor quality
- Increase the seeding rate to get more medium and medium/ small onions, which are preferred at this stage, while encouraging wider acceptance of larger bulbs. If the markets can be persuaded to accept larger bulbs, yield potential will be increased. Increased profitability will allow investment in better equipment and facilities
- Investigate cold-storage options to extend the period of local product marketing. Legislation exists in some countries that protects local producers from imports during certain periods. This may make investment in cold storage more attractive.
Hopefully the onion situation in Zambia will encourage discussion among interested parties. The challenges for growers will always exist, and the only way to overcome these is to plan ahead and seek out opportunities.