Crop details

Sweet potato (viazi vitamu)

Ipomoea batatas

Family: Convolvulaceae

Quick stats

Family	Convolvulaceae
Typical harvest	17.0 t/ha
Varieties	3
Pests & diseases	6
Seasons	3

Crop profile

Growth habit	climber
Days to harvest	150
Main uses	Boiled, baked, fried roots, crisps, flour, animal feed and leafy vegetables from young tops.
Pollination	insect
Origin / where it grows	Sweet potato (viazi vitamu) is widely grown in warm lowland and mid-altitude areas, especially in regions with unreliable rainfall where it helps bridge hunger gaps.

Weather, soil & spacing

Best temperature	21–28 °C
Rainfall	700–1200 mm/yr
Altitude	0–2000 m
Best pH	5.5–6.5
Soil type	Loose, well-drained sandy loam or loam; Sweet potato (viazi vitamu) forms better, smoother roots in friable soils.
Row spacing	90 cm
Plant spacing	30 cm
Planting depth	5 cm
Seed rate	1500 kg/ha
Nursery days	—

Simple notes for farmers

About the crop: This crop has a growth habit described as "climber". You can normally start harvesting about 150 days after planting, depending on care and variety.

Main use: Farmers mostly grow this crop for boiled, baked, fried roots, crisps, flour, animal feed and leafy vegetables from young tops..

Pollination: This crop is mainly pollinated by insect. Keeping flowers healthy and having insects like bees in the field helps improve fruit set and yields.

Where it grows: Sweet potato (viazi vitamu) is widely grown in warm lowland and mid-altitude areas, especially in regions with unreliable rainfall where it helps bridge hunger gaps. It is grouped under: Roots & Tubers.

Best climate: This crop does well in warm areas where the temperature is usually between 21 and 28 degrees Celsius. It prefers places that receive around 700 to 1200 millimetres of rain in a year. It can grow from near sea level up to about 2000 metres above sea level.

Soil: The crop grows best in slightly acidic to near neutral soils, with a pH of about 5.5 to 6.5. It does well in loose, well-drained sandy loam or loam; sweet potato (viazi vitamu) forms better, smoother roots in friable soils.. Good drainage is important, so avoid waterlogged spots.

Plant spacing: Plant in rows about 90 centimetres apart, and leave about 30 centimetres between plants in the row. This gives each plant enough space for roots and canopy to spread.

Planting depth: Dig planting holes or furrows about 5 centimetres deep so the roots sit firmly in the soil but are not buried too deep.

Seed or planting material: Use around 1500 kilograms of seed or planting material per hectare. Spread or plant evenly so the field has a good stand without being overcrowded.

Farmer guide (mwongozo wa mkulima)

Planting: Use healthy, disease-free vines (30–40 cm). Plant Sweet potato (viazi vitamu) on ridges or mounds at the start of the rains, burying half to two-thirds of the vine and firming the soil.

Transplanting: Planted directly using vine cuttings, not from seed or seedlings.

Irrigation: Keep soil moist during establishment and early root formation (first 6–8 weeks). Later the crop can tolerate short dry spells but still benefits from good moisture.

Fertigation: Where drip or sprinkler is available, apply small amounts of NPK and organic fertilizers early. Avoid very high nitrogen, which gives too much vine and few roots.

Pest scouting: Check weekly for Sweet potato weevil, caterpillars, aphids and viral symptoms (yellowing, mosaic, leaf distortion). Remove very sick vines and keep fields clean.

Pruning: No special pruning; avoid cutting too many vines for planting or feed from the same field as this reduces yield.

Harvest: Harvest Sweet potato (viazi vitamu) when roots are well filled and skins are firm. Early-maturing types are ready in about 3–4 months, others in 5–6 months.

Postharvest: Lift roots carefully to avoid wounds. Keep in shade, dry and well-ventilated. For longer storage, cure by keeping in a warm, shaded place for about a week, then store in cool, dry conditions.

Nutrient schedule (mbolea kwa hatua)

#	Stage	DAP	Product	Rate	Targets (kg/ha)	Notes
1	Basal at planting	0	NPK 17-17-17 or 15-15-15	150 kg/ha	N: 25, P₂O₅: 25, K₂O: 25	Apply in bands along the ridge and cover with soil before planting vines.
2	Early topdress	30	NPK with extra K or separate urea + MOP	100 kg/ha	N: 20, P₂O₅: 0, K₂O: 20	Apply around the base of Sweet potato (viazi vitamu) vines when soil is moist.

Nutrient requirements

Nutrient	Stage	Amount	Unit
N	Basal	30	kg/ha
P₂O₅	Basal	30	kg/ha
K₂O	Basal	60	kg/ha
N	Topdress_early	20	kg/ha
P₂O₅	Topdress_early	0	kg/ha
K₂O	Topdress_early	20	kg/ha

Name	Country	Maturity	Traits
Orange-fleshed Sweet potato	KE	120	High vitamin A, good for children and families; medium yield but important nutrition.
White-fleshed high-yielding type	TZ	150	High root yield, popular for boiling and frying.
Local viazi vitamu landrace	KE	150	Traditional taste and texture; adapted to local conditions.

Stage	Product	Rate (kg/ha)	Notes
Basal	NPK 17-17-17 or 15-15-15	150	Used on poor soils to boost early Sweet potato (viazi vitamu) growth.
Topdress (N+K)	Urea + MOP or K-rich NPK	100	Apply early in the season and avoid late heavy nitrogen.
Organic	Farmyard manure or compost	5000	Improves soil structure and moisture holding; apply well-rotted manure before ridging.

Name	Type	Symptoms	Management
Sweet potato weevil	pest	Small holes and tunnels in Sweet potato (viazi vitamu) roots, bitter taste and corky brown patches inside.	Use clean planting material, practice crop rotation, earth up ridges well to cover cracks and harvest on time.
Viral diseases (SPVD complex)	disease	Stunted plants, yellow or purple mosaic patterns, distorted leaves and poor root formation.	Use virus-free vines, remove and destroy very sick plants and avoid taking cuttings from infected fields.
Caterpillars and leaf feeders	pest	Chewed leaves and defoliation of Sweet potato (viazi vitamu) vines.	Handpick where possible and support natural enemies; spray only when defoliation is severe.
Alternaria and leaf spots	disease	Dark spots on leaves, sometimes with yellow halos, leading to early leaf drop.	Use tolerant varieties, improve air movement and rotate with non-root crops.
Root rots in poorly drained soils	disease	Rotted, soft Sweet potato (viazi vitamu) roots and stunted vines in wet patches.	Use raised ridges, improve drainage and avoid waterlogging.
Storage rots	disease	Soft, mouldy roots in store, bad smell and discolouration.	Avoid injuries at harvest, cure roots, keep storage dry, cool and well ventilated and remove rotten roots quickly.

System	Typical	Min	Max	Notes
Smallholder rainfed (low input)	8	5	12	Local Sweet potato (viazi vitamu) varieties, little fertilizer and moderate weeding.
Smallholder rainfed (improved management)	18	12	25	Improved varieties, healthy vines, good spacing, timely weeding and some manure or fertilizer.
High input / good management	25	20	35	Fertile soils, quality planting material, irrigation or reliable rains and strong pest and disease control.

Country	Region	Planting	Harvest
KE	Western and lake Sweet potato (viazi vitamu) belt (long rains)	Mar–Apr	Jul–Oct
KE	Eastern and coastal zones (short rains)	Oct–Nov	Feb–May
TZ	Lake zone and coastal belt	Nov–Dec	Mar–Jun

Country	Region	Suitability
KE	Eastern and coastal lowlands	High
KE	Very cool highland zones with frequent frost	Low
KE	Western and lake region Sweet potato (viazi vitamu) belt	High
TZ	Lake zone and coastal belt	High
UG	Lake Victoria basin and mid-altitude areas	High