Can Kenyan farmers get market for their sweet potato tubers?

Valuable sweet potatoes by Mwangi Mumero

For Charles Muthike, a sweet potato farmer in Ndia Division in Kirinyaga County, demand for this versatile food cannot be met.

“We have lorries and small traders trooping to our farms looking for ready sweet potatoes to buy and sell to the swelling urban population. A large number of farmers in this area have switched from growing maize to fast moving sweet potatoes”, says Muthike, a father of three and a farmer at Karima, near the Nyeri-Nairobi Highway. A bag of sweet potatoes retails at sh 4,500.

With rising shift toward more traditional foods, as lifestyle health issues crop up, ‘orphan crops’ such as sweet potatoes and yams have become favourite for many urban Kenyans eager to drop their ‘junk foods ‘ .

While Central Kenya produces little of the sweet potatoes in the country, the main growing areas are western Kenya- mainly Kakamega, Bungoma, Busia , Homa Bay, Rachuonyo and Kisii counties.

Sweet potato is an important cash crop in Mosocho and Suneka divisions in Kisii county.

In Kisii, an approximately 90 kg bag of sweet potatoes sells at sh 5,000.

Over the years, acreage under sweet potatoes has been rising with average yield at about 10 tons per hectare. Sweet potatoes are adaptable to different agro-ecological zones ranging from 0-2100m above sea level and occasionally are found in altitudes of about 2400m. They thrive at temperatures above 24°C in abundant sunshine.


They require rainfall of 750-1000mm per annum and will need a moderate soil pH of 6.0 for optimum production.


They also require well drained, free soil to allow root development.

Sweet potatoes have a growing period of 3-6 months depending on the variety.


However in the short rains farmers prefer those maturing in 3 months and in the long rains those maturing in 6 months.


Land should be prepared to loosen the soils to make mounds of 80 cm by 30 cm and 1-3 vines planted per mould or on ridges of 90-1500m by 30-60cm along the ridges.


Vines are used for establishment. The shoot vines should be cut 30cm from the growing point before planting.

Cultivation of some of the newly introduced varieties currently under testing by CIP/KARI has lead to higher yields.

Average per capita consumption of sweet potato is about 24 kg per year with higher proportions consumed in the western parts of Kenya .

The white skinned variety has desirable characteristics to both farmers and consumers.

These include short maturity period -3 to 4 months-, high yields, moderate stability after harvesting -up to 7 days- and an attractive yellow flesh.

The major disadvantage of the variety especially if grown for home consumption is that its quality deteriorates very fast when left unharvested beyond 1 month after maturity.

Another variety has a red skin and yellow flesh and matures within 6 to 7 months after planting.

After maturity the tubers can retain their quality for a further 3 to 6 months when left unharvested.

This variety is therefore suitable for cultivation for home consumption and marketing as it can store relatively well after harvesting.

Sweet potato, particularly the yellow fleshed varieties, are good sources of vitamins .

A comparison with other food crops shows that it yields more calories per unit area than either maize or potato and nearly as much as cassava, while its protein yield is far higher than the latter.

Despite the clear potential of sweet potato in helping to meet Kenya's food needs, full exploitation is constrained by its bulkiness, perishability, high cost per unit sold, as well as low consumer acceptability.

Consumers perceive it only as a snack and not as a food which can constitute the main part of a family's diet .

This perception is a substantial barrier to increased sweet potato consumption and hence production.

“ Mostly, people buy potatoes to roast or boil and eat them are snacks. Few customers buy more than five pieces at a time as they are not considered a full meal even at family level”, observes Alfayo Njeri, a trader at the Kibingoti market, located along the Nyeri-Nairobi highway.

At the market, hordes of mainly women traders hawk all types of foods that includes fruits and sweet potatoes to the thousands of road users along this busy highway.

In our urban centres, traders roasting sweet potatoes alongside maize have become a common feature in the streets.

But now researchers have upped the ante and identified another milestone in the nutritive value of sweet potatoes –which are seen as an important food crop in semi-arid lands across the world.

According to researchers and breeders at the International Potato Center (CIP) in San Ramon, Peru, the pigmentation of the purple fleshed sweet potato varieties is due to the presence of anthocyanins.

Studies from Kansas State University have revealed that two of these anthocyanins contain properties inhibiting the growth of cancer cells in the human colon. The high anthocyanin content - an antioxidant- in sweet potatoes prevents cancer and aging.



“My nutritionist colleagues tell me that the anthocyanins in sweet potato are easily absorbed from the digestive tract into the bloodstream, where they may have beneficial effects,” indicates Dr. Ted Carey CIP sweetpotato breeder in Ghana.

Currently, in addition to field testing, CIP scientists also do laboratory tests for nutritional characteristics of these and other sweet potato clones with an aim for future multiplication.

“We are evaluating nutritional components such as beta-carotene, protein, starch and dry matter, and also minerals and micronutrients such as iron, zinc, and magnesium”, explains Genoveva Rossel, CIP’s sweetpotato germplasm collection curator. (ends)