Sweet potato (Ipomea batatas), locally known as “kamote”, is commonly planted in flat to slightly rolling open areas. The crop is also known to be a cheap but excellent source of carbohydrates, vitamin A, carotene, calcium, and phosphorus. It is also a fair source of thiamine and iron but a poor source of riboflavin, niacin, and vitamin C.
A versatile crop, sweet potato has multifarious uses. It is not only grown as a food substitute for rice and corn but also as a potential source of raw materials for industrial uses and food delicacies. sweet potato is being processes into feeds, flour, starch, and pectin for local and export markets. The flour is further processed into fermented products such as, soy sauce and alcohol. When freshly cooked it can be saccharified to produce wine, vinegar, and nata.
Soil and Climate Requirements
Sweet potato can be grown in a wide range of soils, from heavy to sandy. It thrives best in sandy loam soils rich in organic matter with pH ranging from 5.0-7.0 and in areas with uniform rainfall and good drainage.
The crop can be planted throughout the year but the ideal planting time for best varieties is at the onset of the rainy season or immediately after the rainy season when soil is
Choosing the kind of variety to plant is dependent on the purpose for which it is grown. Following are 14 varieties recommended by the Philippine Seed Board. These varieties have inherent characteristics such as, high yield, resistant to pest and diseases, improved nutritional quality, short maturing, and many other desirable characteristics.
Moreover, the varieties recommended for starch processing are those relatively high in starch content.
Cultural Requirement and Land Preparation
To have good root yield of the crop, plow and harrow the soil twice or until soil is loose and friable. Form ridges or furrows of about 30-40 centimeters high by using a carabao-drawn mold-board plow or tractor-drawn disc plow with a distance of about 75-100 cms between ridges.
Use sprouts from roots of previous crop or vine tip cuttings from healthy plants 25 cm long. However, for economic reasons, tip or terminal vine cuttings immediately or you can store them in shaded place but they should be planted within 2 days from the time they are cut.
Plant vine cuttings diagonally on top of ridges during the rainy season to prevent the crop from being soaked under water, or in the furrows during dry season so that moisture reserve in the soil can be utilized by the crop. Expose 2-3 leaves at the tip at a distance of 25 cms between hills. One cutting per hill is equivalent to 33,000 hills per hectare.
Follow the fertilizer recommendation based on the results of the soil analysis. If not available, follow the following general recommendations:
- For poor soil, use 4-6 bags complete fertilizer per hectare;
- For moderately fertile soil, use 4 bags complete fertilizer per hectare;
- For fertile soil, fertilization is not advisable.
Apply fertilizer at planting time at 8-10 cms from the base of the plant or broadcast in the furrows and cover subsequently with soil. The use of compost or organic fertilizers at 3 tons per hectare is highly recommended.
Cultivation and Weeding
If weeds are abundant, shallow cultivation is done 10-12 days after planting. Hilling up cultivation is done at 25-30 days after planting. This is to provide enough soil to cover the developing roots and thus, minimize the entry of weevils that may attack the growing roots.
Pest and Disease Management
Foliar spraying of fevinthrothion at 0.5% one (1) month after planting and twice, at 50 days and 70 days after planting (DAP).
Pest, Description and Control
Sab – Occurs during rainy days infecting the leaves and vines
Control: Spray with copper Oxychloride or Maned (2.008g ai/L) every 10-14 days.
Weevil – Most serious anthropoid pest infecting the roots. Infected roots cannot be eaten by man.
Control: Burn all infected plants. If needed, apply Furadan 36 granules with fertilizer or use healthy plant materials,
Diseases, Description and Control
Stem and foliage scab – Oblong to elongated scabby lesions on the stems and leaves.
Control: Cut off the infected stem
Cercospora leaf spot – Circular lesions with a diameter of 0.5-1 cm which are conspicuous on both surfaces of the leaf. Spots are dark brown to almost gray centers.
Control: Practice sanitation and crop rotation, and use disease-free planting materials. Use resistant varieties.
Blight – Stem are rolled below or above the soil and the organism produces a soft brownish rot. Leaves turn yellow and plants are stunted. Stem Separate easily from the mother plant when pulled gently. Moldy growth appears at the base of the stems.
Control: Observe farm sanitation and destroy infected plants. Deep plowing and maintain good drainage facilities to minimize disease infection.
Nematode – Roots are galled with several egg masses On the surface. Lesion, necrosis and rotting appear usually in cracked.deformed roots.
Control: Treat soil with nematicide which can reduce infection by 85%. Practice crop rotation every 5-10 years with non -host crops, or use resistant varieties.
Soft rot or ring rot – Soft and stringy when opened. Color of the tissue turns from cinnamon to chocolate brown as the rotting advances; forms a ring or band measuring 2.5cm wide which makes the roots to shrive and shrink.
Control: Store roots in clean, dry and well-ventilated storage areas. Care must be taken not to bruise or injure roots during harvest and transport.
Storage rot – Infection is limited to wound periderium which is formed when injured and infected.
Control: Avoid root injury during harvest and transport. Store in a well-ventilated storage house.
Most of the recommended varieties are ready for the harvest 110-130 days after planting (DAP). Harvesting can be determined by root sampling and if desired size has been attained, harvesting can be done anytime.
Before harvesting, cut and roll the vines like a mat, fork, hoe or, pass a plow below the ridges, then hand pick the roots. Handle the roots carefully to minimize injury. Sort out damaged or bruise roots from undamaged ones.
Post Harvest Operation
If possible, use wooden crates for containers instead of gunny sacks to avoid skin damage during handling and transport.
Harvest roots, if properly cured, can be stored even for 3 months by keeping them under room temperature of 115oF or 32 °C with a relative humidity of 92-95%.
source: Palnt Industry Production Guide on Sweet Potato, BPI Sweet Potato Commodity Profile, DA-Eastern Visayas Integrated Agricultural research Center