TT: Ag Ext 14:01

By Rishi Mohansingh (Agricultural Officer 1)

Sweet Potato Production

Sweet potato (Ipomoea batatas L.) belongs to the
family Convolvulaceae and is one of the popular
root crops consumed in the Caribbean. The sweet
potato tuber can be used as a staple and is an Ridge
excellent source of beta-carotene, vitamins, iron, (60 - 90 cm apart)

calcium, magnesium, manganese and potassium Ridge

(30 - 60 cm high)
which are essential for good health. It is also a
great source of dietary fibre especially when eaten Photo 1: Rotavating and ridge formation
with the peel.
Note: No manure is needed, since manure is high
The peel and flesh colour of tubers vary in nitrogen which encourages the plant to
depending on the variety. produce too many vines and little or no tubers.
Land Preparation Variety
Sweet potato must be grown in full sunlight for The recommended variety of sweet potato for
maximum yields. A moderately deep, fine sandy Trinidad is “Chicken Foot.” This is because it
loam soil with adequate drainage is recommended produces good yields, can withstand
for production of good quality tubers. Avoid environmental conditions and is tolerant to the
planting on areas prone to flooding since excess major pests of sweet potatoes.
soil moisture may promote tuber rot. The leaves of the plant are shaped like a chicken
A soil pH of 5.6 - 6.5 is ideal. A soil test is foot. The skin of the tuber is purple to pink and the
recommended to determine the soil pH and the flesh colour is cream to yellow (Photo 2).
amount of limestone and fertilizer needed for
optimum crop growth.
The following land preparation practices are
recommended:

 Clear the area of all vegetation, then plough.

 Broadcast limestone based on the soil test Photo 2: Chicken foot variety
results.
Selection of Planting Material
 Rotavate and make ridges (banks) 30 - 60 cm
(1 - 2 ft) high and 60-90 cm (2 - 3 ft) apart Sweet potatoes are propagated from slips (stem
(Photo 1). cuttings) which can be obtained from the previous
crop. Small tubers can be used to produce nursery
Apply a pre-emergent weedicide to soil plants from which slips are also cut.
according to the manufacturer’s
Select slips from plants 2-3 months old. Use the
recommendation before planting the crop. tips of the plants since they are healthy, vigorously
growing and free from pest and disease.
Preparation of Slips Remove weeds manually or control with contact
herbicides, when necessary, using a shield until
Cut slips 30 cm (1ft) long (Photo 3). Soak them in
vines have covered the soil. Selective herbicides
a systemic insecticide solution for 15 minutes just
can also be used during crop growth.
before planting to destroy any pest which may be
present in or on the pieces of planting material.
Note: Always use protective gear when handling
agricultural chemicals

30 cm
(1 ft / 12 inches)

Photo 5: Good weed control

Photo 3: Slips to be planted Fertilizer Application

Planting Slips Fertilizers provide nutrients to the soil and this
Plant slips 30cm (1ft) apart on the bank (Photo 4). encourages the plant to produce higher yields.
Place the fertilizer between the plants, along the
Make an opening in the soil with a short handled
ridge. If possible cover the fertilizer with soil.
hoe or straight cutlass. Place slip in the opening
and cover ¾ of its length with soil, leaving the tip Two fertilizer applications are required throughout
exposed. the life of the crop (Table 1):
 At planting or within 3 weeks after planting
 At 8 weeks after planting

Table 1: Recommended fertilizer schedule

Amount of
30 cm
Time Fertilizer Type of Fertilizer
(1 ft)
At planting 57 – 85 grams
Apply N.P.K fertilizer high
or three (3) (2 – 3 oz.) per plant in phosphorus, for example
weeks after
Photo 4: Plants 30 cm apart on the ridge Approximately 91 kg/ 12:24:12, to encourage the
planting the
hectare ( 200 lbs/ acre) formation of tuberous roots.
slips
Irrigation
85 – 113 grams Apply N.P.K fertilizer high
Water is needed to keep the soil moist throughout Eight (8)
(3 - 4 oz.) per plant in potassium, for example
weeks after
the life of the crop. However, too much water and planting the Approximately 136 kg/
16:8:24, for the tubers to
bulk up (gain weight) and
lack of proper drainage cause tubers to rot. slips hectare (300 lbs/ acre) have good cooking quality.

Tuber initiation (tuberous roots start to form)

occurs at 4-5 weeks after the slips are planted. Pest Management
The major pests of sweet potato are Sweet Potato
Soil moisture is therefore critical at this time to Weevil (Euscepes postfasciatus) and Sweet Potato
encourage tuber initiation and development.
Borer (Megastes grandalis).
Weed Control  Sweet Potato Weevil
Control weeds (Photo 5) since they compete with The adult female makes holes at the base of the
the growing plants for moisture, nutrients and stem or in tubers near the soil surface, in which
sunlight. They also harbour pests and diseases. they lay eggs. The eggs hatch into larvae (worms)
which tunnel downwards and feed just below the
Remember a pre-emergent herbicide should be
peel layer of the tubers, causing damage (Photo 6).
applied to the soil before planting to suppress
weed growth.
  Soft rot is a fungal disease caused by R hizo-
weevil
damage
pus spp which is a common post-harvest prob-
lem. The infection usually occurs before and
during harvest through injuries on the surface
of the sweet potato. The tissue rapidly be-
comes soft, stringy, and watery with a fermen-
Management of Black Rot and Soft Rot
These diseases can be managed by preparing the
Photo 6: Sweet potato weevil damage land as recommended and maintaining proper
 Sweet Potato Stem Borer drainage throughout the life of the crop. Avoid
growing sweet potatoes in waterlogged soils and
The adult moth lays eggs on the leaves and stems
do not damage the tubers while harvesting.
of the plant. The eggs hatch into larvae (worms)
which burrow into the stems. They continue to Harvesting
feed, eventually reaching inside the tuber where Sweet potato tubers mature and are ready for
they tunnel causing extensive damage (Photo 7). harvesting within 4 - 5 months after they are
planted. Harvesting can be done manually us-
ing a garden fork, or mechanically using a harvest-
er.
borer
damage Delaying harvesting will increase the risk of pest
attack
Once the crop is managed properly each hectare
can yield approximately 11,363.6 – 13,636.6 kg
Storage
Photo 7: Sweet potato borer damage
Harvested tubers must be cleaned of all soil. Soak
Management of the Sweet Potato Weevil the tubers for 10 minutes in clean water containing
and Borer household bleach at a rate of one teaspoon per
litre.
 Soak the prepared slips in a systemic
insecticide solution for 15 minutes before Dip the washed tubers in a fungicide solution and
planting. place in a cool shaded area to air dry.
 Apply a systemic insecticide according to the Place dried tubers in plastic harvesting crates
manufacturer’s recommendations to the plant (Photo 8) for storage and transport.
during the growing period.
For further information refer to the Factsheet
Disease Management entitled: Extending the Shelf Life of Sweet
Two of the most predominant diseases of sweet Potatoes
potato are Black rot caused by Ceratocystis spp Do not use boxes or bags to store and transport
and Soft rot caused by Rhizopus spp. sweet potatoes since they cause injury which
 Black rot is a fungal disease caused by reduces quality and shelf life of the tubers.
Ceratocystis spp which can affect the plant
and tuber at any stage of growth and develop-
ment. The disease symptoms on the plant in-
clude stunting, wilting, yellowing, leaf drop,
and plant death. Large circular, brownish to
black, firm, dry rots are seen on the sweet po-
tatoes mainly when placed in storage.

Photo 8: Harvesting crates

Cost of Production
When preparing a cost of production for a crop Some of these activities include: land preparation,
consideration must be given to all the activities planting, fertilizing. Labour cost for weed control,
involved in growing this crop and the cost of the pest management and harvesting must also be
inputs. considered (Table 2).

Table 2: Estimated Cost of Production / Hectare (2014)

Number of Unit Cost Total Cost

Activity Unit
Units $ $
Land Preparation
 Brush Cut ha 1 1350.00 1350.00
 Plough ha 1 1800.00 1800.00
 Rotavate / Bank Formation ha 1 2000.00 2000.00
Planting
 Slips each 40 000 0.25 10 000.00
 Labour man days 15 200.00 3000.00
Fertilizer
 High Phosphate kg 100 15.00 1500.00
 High Potassium kg 100 18.00 1800.00
 Labour man days 10 200.00 2000.00
Pests and Disease Control
 Pesticide litre 3 750.00 2250.00
 Labour man days 10 200.00 2000.00
Weed Control
 Contact Weedicide litre 3 150.00 450.00
 Pre – emergent litre 3 200.00 600.00
 Labour man days 10 200.00 2000.00
Harvesting
 Labour man days 60 200.00 12000.00
Total Expenditure 42750.00
Expected Yields kg 11363.6 5 56818.00
Profit 14,068.00

Note: The prices mentioned above may vary based on the location.

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Published and printed by
the Extension Training and Information Services Division
Ministry of Food Production
Trinidad and Tobago
December 2014