Sweet potato is one of the most important starchy crops. It is an herbaceous, perennial creeper cultivated as an annual crop.
In Africa, Uganda is the biggest producer of sweet potatoes and third in the world after China and India.
The orange flesh variety is preferred because it has high amounts of beta-carotenoids, associated with preventing vitamin A deficiency, which causes blindness in both adults and children.
Scientists at National Crop Resources Research Institute (NaCRRI) Namulonge have been breeding orange fleshed varieties through an initiative driven by the International Potato Centre for farmers countrywide to adopt since it contains Vitamin A and iron nutrients.
The institute got the opportunity to disseminate these varieties through primary schools in Mukono and Kamuli districts where vines were given to each pupil to take to their parents for onward multiplication and growing the same.
Vines were procured from established multipliers and distributed to farmers through the school children. The modal was that 120 vines of different varieties are given to each child to take to the family and in turn this family gives double the vines to two households.
The results indicated more than 600,000 hectares of sweet potato was grown. There were demonstration gardens at schools for sensitising children in the agronomy practices and they taught the parents how to manage their farms.
Seeds of Gold spoke to Dr Gorrettie Ssemakula, the programme leader for sweet potato breeding at NaCRRI who spearheaded this initiatives.
She points out that farmers in Uganda have a challenge of accessing improved varieties and this leads to low productivity. So far, Naro has released 27 varieties of the crop.
“We have several sweet potato varieties with varying characteristics and attributes, some have high dry matter and are traditionally the most preferred types, while others have low dry matter and are less preferred,” says Ssemakula.
You can also differentiate sweet potatoes by their skin and flesh colour. The most predominant skin colours are white and pinkish while the flesh colours are mostly yellow and orange.
Outstanding sweet potato traditional varieties grown in Uganda include; Tanzania, Tororo 3, New kawogo and kakamega. The orange fleshed varieties include NASPOT8, 11, 12, 13 and NAROSPOT1, 2, 3 and 5.
They have good storage root, high dry matter content, high level of beta-carotene and resistant to sweet potato virus.
Sweet potatoes can be produced in low and high altitudes as long as the soils are fertile.
Seedbed for sweet potato should be fertile and well prepared without big soil clods.
The huge soil clods would interfere with tuber development later during growth and development of the crop. It can be on flat mounds or ridges where three to four vines are planted with spacing of 1cm apart. This applies to places such as Kabale and it contains soil erosion.
How to propagate the plant
Farmers can propagate sweet potatoes as vegetative using stem segments called vines.
These are taken from the top of the old stems and caution should be taken to avoid chloric, mottled, wrinkled or vines with mosaic patterns.
Plants with mosaic patterns could most likely be having a viral disease. Farmers can practise rapid multiplication practices to multiply vines.
Here you use two node cuttings, make a bed spacing 2cm apart, apply aerial fertiliser and in two months the planting material will be ready for planting.
Farmers can also use the conventional method by cutting vines and planting them in a nursery.
Once they have grown 30cm it is ready for planting.
Sweet potato is either planted in mounds or on ridges using vine cuttings.
Vines are the mature stems and are taken from the shoot.
A good vine cutting should be about one foot long or about six nodes and should be disease free.
When mounds are used, they should not exceed a height of 1m in height and diameter. The size of the mound however varies with the type of soil.
In soils that are prone to drying, small mounds are used; big mounds in such a case are over exposed to sunshine and they dry out very fast. The numbers of vines used do vary, as small mounds will take few vines and the big mounds accommodate more vines.
Planting is mostly done by hands, but you can plant sweet potatoes using forked sticks in some cases.
Vines for planting should be picked and allowed to wilt in the shade for a week before planting.
This ensures that the vines do not break during planting as fresh vines are brittle. These vines also root easily and ensure faster establishment of the crop in the soil.
Sweet potatoes should be kept weed free in the first months and this is done by weeding around the ridges/mounds.
Weeding is normally done by hand. After about two months, the canopy of the crop is normally big enough, covering the ground and this helps to keep away weeds.
It is important to cover cracks arising from growth of the tubers with soil, otherwise if left open will attract weevils that will infect the tuber.
Pests and diseases
The most common pest is weevils; others are caterpillars and grasshoppers which can be controlled using appropriate Pesticides
The diseases include Sweet Potato Virus disease and Altarnaria affecting the leaves and stems and Fusarium wilt among others
Farmers are advised to use resistant varieties such as the Orange Fleshed varieties and they should avoid spreading susceptible seedlings.