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Last Update: 23 Apr 2018
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Department of Agriculture Sarawak, 7th, 12-14, 16-17th Floor, Menara Pelita, Jln. Tun Abdul Rahman Yakub, Petra Jaya, 93050 Kuching, Sarawak

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Sweet PotatoSweet Potato

INTRODUCTION

Scientific Name
:    Ipomoea batatas
Origin:    Tropical America
Family:    Convolculaceae
Suitable planting at :    Area 40o U to 30o S.
Nutrient:    Carbohydrate, Vitamin A

TYPE :

Wet type

This yam turns soft when boiled or fried. In Malaysia, yam which is red skinned is grouped with the wet variety. This type usually is high-yielding. Chinese yam is in this group.

 

Dry type

This yam does not turned soft when fried or boiled. Normally, it skin is white and the yield is lower compared to the wet type. Gendut variety is in this group.



VARIETY
:
   

(i)    Gendut Variety (MSP 94)

The variety was obtained from MARDI Semenanjung.
Starch contain :    23%
Cerotena contain :    31 ug/100g
Brix:    10.0 %
Nutrition quality:    the yam turns soft and dry texture when boiled or fried.

Its characteristic edible quality makes it suitable for fresh food preparation as well as for substituting potatoes in curried dishes.

Therefore, the Department of Agriculture had recommended this variety to the farmers.

 

Gendut Variety Characteristic:

The leaf is heart shaped, its leaf shoot is light green and the leaf stalk is green. The stem is also green, the tuber skin is yellowish blonde, smooth and thin while its content is white in colour.

Picture
>> Gendut Variety

(ii)    Chinese Variety

This variety is popular among the local people. The flesh turns soft and a bit wet when boiled or fried.

Picture
>> Chinese Variety

 

Chinese Variety Characteristsic:

Heart-shaped leaf light-green leaf shoot with purple-laced leaf edge and green leaf stalk with purple color at its division with the stem.

The stem is almost all purple in colour, yam skin is orange, wrinkled and thin while the contain is also orange in colour.




SOIL SUITABILITY

The plant needs hot and dry weather for about 3 months in order to get high yield.

It grows well in sufficient humidity but it doesn't stand if planted at the water logged soil. It grows best on sandy loam soil with high organic matter and good water absorption.

It is not suitable if planted at the clay soil as the soil is not tilth for optimum tuber growth. It is also suitable to be planted at a well drainaged matured peat soil.


PLANTING

Land Preparation

The land must be plough and turned over. Generally, one ploughing and turning over is sufficient. Planting bed of 60 cm wide and 30 cm high is prepared.

Preparation of Planting Material

Sweet potato can be propagated in two ways; by its tuber and its cuttings. Cuttings are cheaper and easier. To obtain planting materials of about the same age, propagation period required is 50-60 days. Then the stems are cut at 20-30 cm for field planting.

Field Planting

The cuttings are planted slanting, with about 20 cm of the cutting is under the soil and 10 cm above the soil surface. Planting distance recommended is 1.0m x 0.3 m. If the weather is very hot and dry, water the newly planted cuttings once a day. The creeping plants should be collected and placed onto the beds to avoid the roots from growing from the nodes along the stems. If this is allowed, small tubers will be produced at the main stem. This could be carried out once a month depending on the growth.


FARM MANAGEMENT

Weeding

Weeds should be destroyed by using hoe or weedicide. Pre-emergent weedicide do not endanger the newly planted cuttings. But is advisable to carry out the spraying before planting.

Manuring

Liming at the rate of 1.0 mt/ha is necessary 3 weeks before planting. Manuring at the rate of 600 kg of 15:15:15 per hectare is applied one weeks after planting. One month after planting, another 600 kg of 15:15:15 is applied.

The fertilizer is applied around each plant. Additional fertilizer at a reasonable rate is applied if the growth is not encouraging. An imbalanced manuring can cause the plant to produce more leaves and less tubers.


HARVESTING

Sweet potatoes can be harvested 4-6 months after planting.

Gendut and Chinese varieities can produce about 20-25 mtan per ha if planted at mineral soils with recommended agronomic practice.

 

PEST AND DISEASE

Disease

(i)    Scab (Agent: Elsinae batatas)

Symptom: 

This pathogen causes spots on leaf vein, petiol, leaf and stem. The spots are tiny, roundish to elliptical in shape which can then turn chocolate enclosed in purple.

The infected part turns misty to develop into a scab, the tissues are changed in form, blemished and growth is stunted.

Recommended Control:

  1. Use resistant variety
  2. Spray fungicides Benomyl (Benlate), Copper oxychloride or Maneb)
(ii)    Cercospora Spot Leave

Agent:    Cercospora timorensis

Symptom:

The tiny spots are reddish yellow, round in form and L-shaped to the leaf. Serious infection causes the leaf to collapse; often occurring under humid weather condition.

Recommended control :

Serius infection - Maneb or Zineb.

Pests

(i)    Beetle (Cylas formicarius)

Sweet potato beetle (Cylas formicarius) is the most dangerous pest causing serious damages to sweet potato plant, which attacks all parts of the plant: tubers or roots, stems and leaves. The recommended control is crop rotation, use pest-free planting material, planting material treatment and immediate harvesting

Recommended control:

  1. Practice crop rotation
  2. Use pest-free planting materials
  3. soak the cutting in pesticide solution for 30 minutes before planting
  4. Broadcast carbofuran pellets around crop base
  5. Harvest the yam tubers as soon as they are ready for harvest
  6. Cover up tubers which are exposed.
(ii)    Rat

Rats usually eat exposed food at soil surface. Serious rate infestation can cause serious loss. Bait laced with the poison Walfarin may be used (against the rats).


COST PRODUCTION AND INCOME PER SEASON ESTIMATES

Estimates for:  

Planting density : 33,333 cut per ha
Planting distance : 1.0 m x 0.3 m for 1 ha
Maturity Period : 4 months
Varieties : Gendut or Chinese



Production Cost

Item Price (RM) Total work day Family labour per day (RM) Cost (RM)
1.    Seeds
-
-
-
-
2.    Area and beds Preparation
800.00
-
-
800.00
3.    Planting
-
16
240.00
240.00
4.    Watering
-
12
180.00
180.00
5.    Manuring
381.09
5
75.00
456.09
6.    Weeding
174.50
10
150.00
324.50
7.    Pest Control
444.50
10
150.00
594.50
8.    Harvesting
-
48
720.00
720.00
Total of Cost Production
1,800.09
101
1,515
3,315.09

Estimated Income Per Season:

Yield
(kg/ha)
Income Income
(RM/kg)
    0.50 1.00 1.50
Low
(7,000)
(i)   Gross
(ii)  Net
(iii)  Family
3,500.00
184.91
1,699.91
7,000.00
3,684.91
5,199.91
10,500.00
7,184.91
8,699.91
Moderate
(11,000)
(i)   Gross
(ii)   Net
(iii)  Family
5,500.00
2,184.91
3,699.91
11,000.00
7,684.91
9,199.91
16,500.00
13,184.91
14,699.91
High
(15,000)
(i)   Gross
(ii)   Net
(iii)  Family
7,500.00
4,184.91
5,699.91
15,000.00
11,684.91
13,199.91
22,500.00
19,184.91
20,699.91

Source:    Penanaman Ubi Keledek, Editorial Section, HRDE Branch, Department of Agriculture

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