Sweet potato (Ipomoea batatas Lam), popularly known as "kamote" is one of the staple food of the Filipinos. It is rich in food energy, vitamins and minerals essential for the human diet. It is usually eaten boiled or baked, and may be candied with syrup or processed into puree. It is a source of starch, glucose, syrup and alcohol and now used as a major ingredient for feeds. Its tops and leaves are utilized as a pot-herb and the vines as fodder for livestock.
Among the roots, bulbs, and tubers, sweet potato has the highest consumption volume. The national per capita consumption is 10.9 kilos. In the Bicol Region, sweet potato is planted everywhere because it requires less cultural management. (Source: Department of Agriculture Bicol Region, Date accessed 20 March 2014)
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Soil and Climatic Requirements
Sweet potato can be grown twice a year anywhere in the country and in a wide range of soil types, from heavy to sandy. It thrives best in areas with sandy loam soil, uniform rainfall and good drainage. Dry season crop usually produces better quality roots because climate favors root development.
The crop can be planted anytime of the year so long as the soil is sufficiently moist. It is usually planted at the onset of the rainy season or immediately after when the soil is still moist.
The area is plowed at least twice and thoroughly harrowed, when carabao drawn implements is used. Make furrows or ridges at 0.80 cm. between rows.
There are two types of propagation:
- Sprouts from tubers.
- Terminal cuttings.
- Terminal cuttings are favored because they are available throughout the year
- Easier to gather and free from soil borne diseases.
- It gives better growth and yield compared to middle and basal.
- Gather tip cuttings 30 to 35 cms. long, a day or two days before planting about 40,000 tips are needed to plant 1.0 ha.
- Remove older leaves to reduce transpiration and to keep cuttings longer if necessary.
- Store the cuttings under a cool, moist and shady place for not more than 7 days.
Procedure to be followed:
- Before planting, cuttings should be dipped in a solution of insecticides and fungicides
- Plant one cutting per hill at a distance of 0.35 m between hills and 0.80 m between rows.
- Bury about 1/3 of the basal part of the cuttings into the soil when there is enough soil moisture and 2/3 when the soil is a bit dry. On wet soil, vertical planting is recommended and horizontal or slanting when the soil moisture is inadequate, to prevent the cuttings from drying up.
- Re-plant 1 to 2 weeks after planting if necessary.
Sweet potato needs less phosphorous than potassium and nitrogen. Good fertilization rate is 60 kilograms of nitrogen, 30 kilograms of phosphorous and 120 kilograms of potassium (60-30-120)
Apply one-half of the fertilizer rate before planting, either under ridge or furrows and the other half top dressed two or four weeks after planting. This split fertilizer application is better than the single application technique. The use of manure or compost is also beneficial especially in areas with poor sandy clay soils.
Sweet potato is usually harvested four months after planting. However, this varies depending on the variety and climatic incidence. Some varieties mature as early as 90 days and some mature 100-120 days for dry season and 150 for wet season (DAP).
In some cases, readiness of the crop for harvesting is indicated by yellowing of the leaves. Maturity can also be determined by cutting few roots and exposing them to the air for an hour. If the cut surface dries up, the roots are mature but if the sap continue to flow and remain sticky, the roots are still immature
If harvesting is done too early yields are low but if the crop is left in the ground too long, the roots becomes fibrous, unplantable and are prone to be attacked by sweet potato weevil and various rots
In harvesting, the following steps are involved:
- Cutting and rolling of vines to one side of the field
- Passed 3 to 4 times along the rows designed for sweet potato harvester
- Follow the harvested one at a time and pick-up harvested roots
- Remove soil particles from roots
- Sorting roots into large, medium, small and etc
- Discard roots damaged by sweet potato weevil
- Place the roots in container for market or home use.
Sweet potato is affected by different diseases in the field, affecting the storage life of the roots. These diseases can cause economic losses in yield depending upon the severity of infection.
The term "packaging" refers to the operation of producing packages that used to contain protect; identify and sell a product. It involves not only the packaging of the crop from the farm to the market or storage and to the end-user. In this case, different types of containers are used needed from one to another i.e., farm to storage within storage and in the market.
One way of obtaining good quality products is by employing packaging methods and using suitable containers during storage. A good pack lessens scratches, bruises and injuries during transport from the field to any point, hence, maintains the quality and good appearance of the roots. If the roots are to be stored, proper packaging lengthens the storage life of sweet potato roots. It also protects against moisture loss (weight loss) and thus prevent dehydration.
Benefits that could be derived from packaging:
- More efficient utilization of storage place. More roots can be accommodated into a given area, if the roots are placed in containers, since they could easily be piled or top of each other.
- Roots properly placed in containers, they can be easily arranged in such a way that proper ventilation of the roots is being facilitated.
- Keep the floor clean.
Packaging materials to be used:
Although there are no packaging containers specific for sweet potato, some of those available have sufficient stocking strength and are considered ideal because they protect the roots from being injured or compressed which prevent the roots from bruising, crushing.
Post-Harvest Handling and Storage of Sweet Potato
Postharvest handling of sweet potato
Thrust in food production must be matched with improvement in the postharvest handling of the produce. Proper handling at all stages of post production from harvest time until the products reach the ultimate consumer is therefore essential.
One postharvest problem is carelessness in handling operations. Throwing dug up sweet potato roots some distance away to a container or into a pile is a common practice during harvesting. It is not realty to handle the roots as eggs, but it should be handled carefully because the impact or compression that each variety of sweet potato can tolerate without significant loss in quality and storability. It is best however then that sweet potato roots should be handled as carefully as possible.
Sorting and Grading
Sweet potato roots should be placed in cool, shaded and well-ventilated areas for sorting and grading. Mixing roots of different qualities (large, medium, undersize, etc.) will lower the average quality and value of sweet potato. In this regard, classify the roots into large, medium, small undersize, damaged, etc.
Grading helps buyers select most suitable for the purpose they like. It aids in marketing of sweet potato by establishing common language for wholesale trading and means of establishing high prices. Grading permits a buyer to purchase more precisely what he wants and makes the marketing system more efficient. When sweet potato is ungraded, buyers tend to extensively haggle buying to get reasonable price. Usually, buyers are prone to offer low prices for the ungraded causing the farmers to receive lower profit or possibly loss.
Source: Department of Agriculture Bicol Region, Date accessed 20 March 2014