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Scientific Name: Ipomea batata

Local names in Kenya: Viazi vitamu, Rabuon, Mabuoni, Amapuoni

Overview of Sweet Potato as food and fodder

Livestock feeding during the dry season is a major challenge to dairy producers in the dry areas of western Kenya. Alternative sources of livestock feed to spur livestock production and to free cereal biological efficiency as food and shows highest productivity (35-45t/ha). It has a relatively short vegetative cycle (4-5months), hence fitting nicely into tight cropping systems.  The dry matter content of sweet potato varieties ranges from 21.7 to 34.78% which is more than cassava. Its tubers can be given to all ruminants as fresh, chopped tubers, dried chips, and silage for energy supplements along with locally available grasses during the dry season. The vines contain between 15 and 30% protein. supplies for human consumption are receiving closer attention. Sweet Potato is a crop that is not only common with farmers in western Kenya but also has higher Animals fed with Sweet Potato vines benefit from its high nutritional value.  Sweet potato vines have a higher nutrient content than does Napier grass and are normally fed to cattle as a supplement. They are particularly recommended for calves as they increase the growth rate and promote rumen development. They are also good for recently calved and sick animals. They increase milk yield when fed to lactating cows. Their main setback is relatively high moisture content. Although sweet potatoes are a good source of energy (roots) and protein (vines), they are highly perishable. In order to make good use of sweet potato residues (vines and roots), there is a need to conserve them in form of silage which has the potential to mitigate seasonal feed shortages and help cope with seasonal feed price fluctuations that many smallholder livestock farmers experience. It also provides an opportunity to reduce waste in the urban market and at the household level as well as it can open up business opportunities for youth and women.



Site Selection
Select Suitable Agro-ecological zones fit for growing sweet potato.

Suitable zones in Western Kenya are lower highlands (LH) 1, 2; upper midlands (UM) 1,2,3,4; and lower midlands (LM) 2,3,4.

Rainfall: A well-distributed rainfall of 750–1000 mm per year is considered most suitable for the crop with a minimum of 500 mm in the growing season.

Temperature range: For optimal growth, day temperatures should range between 15 – 30°C.

Soils: The crop grows on a variety of soils, but well-drained light and medium-textured soils with a pH range of 5.5-7.0 are more favorable. Sandy loam soils give the best yields. Altitude range: Sweet potato can be grown at altitudes from 0 – 2500 m above sea level, depending on variety, but it performs best in an altitude range of 1000 – 2100 m.a.s.l. The site selected should be at least 50 meters away from old sweet potato crop to minimize spread of pests and diseases from old to new crops. In a proper crop rotation, sweet potato can follow either cereal such as maize, sorghum, rice, finger millet or legumes such as beans. .

Site Selection
Potato requires a loose soil structure to allow for good tuber development

Prepare land using either a hand hoe or oxen/tractor drawn plough.Plough deep enough for root expansion. Deep cultivation (at least 15cm) improves aeration, water infiltration and ensures good drainage. Harrowing may be necessary to ensure an appropriate tilth. .

Land Preparation
Potato requires a loose soil structure to allow for good tuber development

Prepare land using either a hand hoe or oxen/tractor drawn plough.Plough deep enough for root expansion. Deep cultivation (at least 15cm) improves aeration, water infiltration and ensures good drainage. Harrowing may be necessary to ensure an appropriate tilth. .

Selection of Planting Material (Pre-planting)
Sweet potatoes are propagated vegetatively using cuttings (vines) from healthy vigorous crop (2-3 months old).

Vines from old crop produces a less vigorous crop and poor yields due to heavy infestations from pests and diseases. Cut the top 30cm of the vine for best results. The middle part of the stem can also be used if there is a shortage of planting material. Plant the vines within 7 days after cutting to avoid loss in quality. If not planted on time, cuttings should be stored under shade or in a cool well-aerated place. During storage, roots develop at the base of the cuttings and the vines harden thus enabling faster establishment. .

Sweet Potato Varieties for Food and Feed
Select the variety desired depending on adaptability to the region, consumer demand/preference; and pest/disease resistance.).

The main fodder varieties grown in Kenya include Kiganda, Muibai, Sandak, Mugande, KSP 20, Mafuta, Musinyamu, Wagabolige and Helena. Most of these cultivars are suitable as dual purpose. .

Plant sweet potato early at onset of rainy season to get best results.

Vines can be planted in ridges, flat or in mounds of varying sizes. Plant sweet potato vines (cuttings) 30 cm long at a spacing of 90 cm between rows and 30 cm within rows. A mound should be 100cm wide and 60cm high, the distance between mounds should be 1m. Ridges are spaced at 0.5m from each other. The planting operation involves pushing the lower part of the vine cuttings into the soil, such that they are nearly horizontal. Three vines are planted per mound (4-5 vines can be planted on extremely large mounds). Vines are spaced 30cm from each other on mounds or ridges. For fodder production there is no advantage of ridging or mounding during seedbed preparation. .

Apply composted animal manure before planting or alternatively 2 bags of Mijingu Rock phosphate at planting.

Organic fertilizers (composted manure, green manure) releases nutrients slowly and therefore should be applied as a basal fertilizer (incorporated when making mounds or ridges). During growing period, the plants form dense foliage with rapid vine growth..

Weed Management
Weeds cause significant losses as they compete with main crop for nutrients, water and sunlight.

Weeding should be done twice; at 2 weeks and at 4-5 weeks after emergence. Avoid weeding after flowering because it predisposes the crop to infections and may damage the developing tubers.Keep the field weed-free within the first two months after planting. Thereafter the vines will have spread to cover the soil and smother the weeds.

Pests and Disease management
Sweet potato production can be constrained by pests and viral diseases that cause yield losses, potentially from about 50 percent to even as much as seventy percent.

Pests Sweet potato weevil Cyclas spp. The sweet potato weevil is the most serious insect pest of sweet potatoes worldwide. They are small black beetles. Adult weevils feed on the vines and tubers, while the larvae make tunnels into the vines and tubers. Damaged tubers become unmarketable, bitter, with bad smell. Diseases Several viruses currently recognized as significant causes of diseases to sweet potato (SP) in Kenya, listed roughly by their frequency of occurrence, include:

(a) Black rot: Caused by the seed-borne fungus Ceratocystis fimbriata. Symptoms include large circular, brownish to black, firm, dry rots on sweet potatoes. In plant beds symptoms include plant stunting, wilting, yellowing, leaf drop, and plant death. Rots may continue developing in storage. Infected roots have a bitter taste.

(b) Ring rot: Caused by the common, soil-borne fungus Pythium spp, which also parasitizes many other plants. Infected roots have sunken, chocolate colored lesions that tend to extend laterally and often form a ring around the sweet potato. The soft rot extends into the interior. Losses generally occur late in the season during cool, rainy periods. Symptoms may be confused with Rhizopus and bacterial soft rots and souring. Ring rot usually does not spread in storage. The disease can be managed by harvesting prior to cool, wet periods.

(c) Fusarium root and stem rot. Caused by the fungus Fusarium solani, is a common field and storage rot. The rot extends deep into the sweet potato and is firm and dark tan in color. Internally, elliptical cavities form in which a white mold develops. The soil-borne disease may be spread by infected transplants. The base of mature stems may become swollen and distorted. Management: Generally, pests and diseases can be managed by applying integrated pest management (IPM) methods. These include:

(a) planting healthy vines,

(b) planting a new crop 50m away from the old field,

(c) early planting, earthing up, crop rotation,

(d) destruction of infested plant parts and

(e) destroying volunteer crops. 


Harvesting and Feeding
First harvest when the vines cover the ground i.e. 3- 4 months from planting.

There are three methods of harvesting: 1

) Cut forage at interval 6 - 8 weeks;

2) Selectively plucking vines at the length 1/2- 1 meter from the tip at an interval of 3- 4 weeks; and

3) Those planted on ridges cut the vines extending beyond the ridges and leave a stubble height of 5cm (2in) from the ground level. Carry the cut material to the cow and feed up to 15 kg fresh material per day, as a supplementary feed to Napier grass or other basal feeds.

Production potential (Yield)
Sweet potato can produce 35 – 95 bags per acre and 13,500 vines/acre.

If the crop is harvested too early, the roots will not be fully developed. Delayed harvesting on the other hand leads to fibrous and pest-infested roots..

Sweet Potato Silage
Sweet potato silage is a method for preserving vines and roots in a succulent condition in a silo.

Well-made sweet potato silage is a wholesome and nutritious feed for all classes of dairy cattle. Sweet potato silage is made by fermenting chopped vines and roots of noncommercial value in the absence of air and can be stored for up to a year. Its protein content and digestibility makes it an excellent complement to rass feeds. Silage can be made with only chopped vines or combined chopped vines with roots (at a ratio of 70:30) or with a grass like Napier grass. The use of a fermented starter, like molasses, improves the process of fermentation and nutrient content. Use of sweet potato silage can significantly reduce feeding costs. However, sweet potato silage is underutilized in Western Kenya because it is largely unknown. The best use of sweet potato silage is during periods of feed scarcity. Vines and roots can be chopped either manually (panga) or with a motorized forage chopper. The former is recommended for small scale producers while a motorized chopper (costing about Kshs 35000 - 55000 depending on the capacity) is more suitable for large scale producers or farmers’ groups.

 The greatest challenge that farmers face when making sweet potato silage is how to control the high moisture content in the sweet potato vines. Typically, vines are wilted prior to making silage to remove excess moisture. However, many farmers have found it difficult to wilt sufficiently large volumes of vines which often results in spoilage during the silage making process. The spoilage is due to excess water accumulating at the bottom of the silage container. The improved plastic tube silo is an innovative way of enhancing compaction and draining excess effluent (liquid waste) from the tube silo method of producing silage. ..


Mugo, B.J. and Gatwiku, S. Livestock fodder from Sorghum and sweet potato vines (KALRO).
Sankaran m. et al 2012 Sweet Potato as animal feed and fodder.