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Agronomist notebook: Here’s the best way to harvest sukuma wiki

Friday March 13 2020
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A farmer harvests sukuma wiki on her farm in Nyandarua. Under good management practices, the vegetable can be harvested for four months depending on the variety. PHOTO | FILE | NATION MEDIA GROUP

By ANN MACHARIA

Sukuma wiki (collard greens) is a much-loved plant that is grown for both subsistence and commercial purposes.

The vegetable has a ready market, is easy to grow and cook, thus making it a favourite for both consumers and farmers.

But while sukuma wiki appears hardy and needs little input from farmers, one of the challenges the crop faces regularly is stem rot. I recently met a farmer grappling with the problem in both his greenhouse and field crops.

He was rotating tomatoes with the crop, which he had planted to control pest and diseases and improve the soil structure.

Initially, the crop had thrived until the first harvesting was done. The demand was high because he had planted them soon after the prolonged rainfall last year. After one week of harvesting, the plants started to rot, especially on the stems.

One could easily see broken stems that had rotted. In some plants, the leaves had brown spots and the crops were wilting. Eventually, the whole crop was destroyed.

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The infection was mostly in the open field as compared to the greenhouse, where temperatures were high, facilitating drying-out of water from the stems.

The plants had developed stem rot due to poor harvesting techniques, which created an entry point for pathogens.

During the rainy season, water enters the stem through the injuries, creating a conducive environment for the pathogens to thrive and making the stem to rot. This normally reduces the harvesting duration.

From this scenario, it’s evident that a farmer can have a very good crop but end up with losses due to poor harvesting techniques.

When harvesting sukuma wiki, leave at least 2cm stalk on the stem and allow it to drop on its own. Cutting next to the stems causes injuries, which serve as entry points for pathogens.

AVOID EARLY HARVESTING

Also, ensure you leave two to three mature leaves to ensure continuous production of the crop. And when weeding, be careful to avoid causing injuries to the stems with your jembe (hoe).

Avoid overhead irrigation and over-watering as this creates a conducive environment for the disease to thrive. During seed selection, select seeds that are more resistant to stem rot.

The plants are normally ready for harvesting four weeks after transplanting. Then harvesting begins soon after. But avoid early harvesting since it results in declined production and late harvesting results in overgrowing of the leaves.

Do the harvesting at least twice per week until the crop is removed. However, this depends on the variety and soil nutrition. Avoid picking the terminal buds found at the top centre of the plant as these help keep the plant productive.

In case of infection, the affected stem should be uprooted and disposed of properly to prevent spreading of the disease.

Under good management practices, sukuma wiki can be harvested for four months depending on the variety. For good production, plant both sukuma wiki and spinach since their marketing goes hand in hand.

However, do not plant both spinach and sukuma wiki next to each other as such mixed cropping results in competition for nutrients.

Spinach is not highly susceptible to stem rot but it is easily affected by caterpillar attacks, especially during the rainy season.

To curb this, maintain good farm hygiene and ensure the old crop is removed as it normally acts as a breeding ground for pests and diseases.

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