LSU expert develop new harvesting tools for sweet potato

So much for laborious and slow harvesting methods. Sweet potato farmers in the country can now look forward to a more productive enterprise with the development of a tractor drawn harvester.

Alan Loreto and Manolo Loreto Jr. Researchers of the Philippine Rootcrop Research Training Center (PRCRTC) in Leyte State University (LSU) came up with this harvester featuring a single-row vine cutter and digger after a uear of research in their Bureau of Agricultural Research funded project.

Initial on-station trials revealed that at 1,300 rp the vine cutter could effectively eliminate unwanted vines, leaving only the stalk close to the sweet potato roots to facilitate easier digging. The researchers computed the vine cutter capacity at 1.33 hectares per day at a speed of 2 km per hour.

Morever, the single-row sweet potato digger, another feature of this tractor-drawn harvester, could harvest 1.08 hectares per day at 2 km per hour. The researchers likewise noted that this digger could harvest sweet potato roots with minimal damage on them.

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Breaking Potato tuber Dormancy

Breaking Potato tuber Dormancy or Pagpapatubo


Planting of sprouted seed tubers result in early and uniform emergence. The dormancy of potato seed tubers may be broken by various methods:

  1. Use fluctuating temperature. Bring tubers to a warmer area for a short period before returning them to the farm or storage room. This could be done by holding tubers above the cooking areas.
  2. Use chemicals such as calcium carbide (CaC2) and gibberellic acid (GA3).

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Storage of seed potato

Storage of seed potatoes


The recommended storage for seed tubers is diffused light store (DLS). Tubers are placed in chiting trays, racks or shelves in a building or storage where light can pass through  transparent plastic sheets or fibreglass walls.

Sprouts from DLS have study sprouts. Sprouts from dark storage have long ad etiolated sprouts that are susceptible to damages during handling.

Vacant rooms or unused buildings can be renovated to serve as a diffused light store.

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Potato Postharvesting part 2

Sizes of potatoes

The sizes of potatoes commonly used in the market are : small, medium , big, extra, extra large, super and jumbo. Sizing, however, varies from one farmer to another and usually depends on market price. When market price is high, farmer or trader lowers the base limit for each size.


Grading of potatoes

After sizing , potatoes may be graded based on the crops general appearance, quality and condition. Some factors considered in grading potatoes are:

          Degree of skinning;


          Presence of growth cracks;

          Disease and insect damage;


          Discoloration (i.e greening) and




Packing of potatoes is done right in the field, at the warehouse or at the trading post.

Packing materials used are bamboo-weaved baskets, crates, plastic or polypropylene sacks (50-70 kg capacity) and polyethylene bag (10-25 kg capacity) Using baskets, cushion materials should be wrapped around the sides to prevent bruises from sharp edges of bamboo weaves.

Transparent plastics are usually preferred for easy inspection of quality. The practice of “bomba” system (mixtures of sizes quality) is not recommended.


Transporting / Bulk Handling

Carefully transport potatoes to avoid damage such as feathering/maladlad and bruising. Place newspapaers or jute sacks in between bags of potatoes to reduce damage during transport.


Use any available liner on the floor and sides of the vehicle before loading the tubers in bulk or buhos to reduce mechanical damage. Load potatoes in crisscross manner for proper aeration and close to each other to avoid impacts during the travel.



Potatoes are living organisms that are subjected to losses during their autonomous life thus their life process require energy supplied from its own reserves.

During storage, tubers continue to lose weight because of changes in their physical and chemical composition that affect quality. Hence, proper storage techniques must be practiced.


Storage of ware potatoes.

In building storage. Pile bags/sacks of tubers in heaps in multi-purpose or adapted building for a short period of time (two days to one month).

Storage of table potatoes for a longer period of time should be in dark area to avoid greening. Green tubers are  unfit for food. However, for a shorter period of storage tubers could be piled/spread on a cool place then prevented from light by using dried leaves or grasses or “tolda”.

Storage temperature is an important factor in storage. Generally, the lower the temperature, the longer is the storage period. However, for a shorter period of storage tubers could be piled/spread on a cool place then prevented from light by using dried leaves or grasses or “tolda”.

Storage temperature is an important factor in storage. Generally, the lower the temperature, the longer is the storage period. However, temperature below 10 degrees Celsius may decrease the processing quality and acceptability of processed products because of dark coloration of processed products.

During the rainy season, blowers can be used to dry potatoes.

In the absence of blowers, simply spread tubers on the floor to air dry.

Once dry, use canvas sheets or tolda or dried leaves e.g. banana leaves/grasses to cover potato pile against light. Light causes undesirable greening in the table potatoes.

Do not prolong the use of canvas because moisture may develop. Moisture inside the canvas may cause the tubers to decay.

To reduce damage due to condensation of moisture, cover tubers with newspapers before placing the canvass. Or better still, put tubers in dark store.

Store potato tubers or table potatoes in a well-ventilated dark storage room to prevent greening. Green potatoes taste bitter because of a poisonous substance known as solanine.

Greening is a varietal characteristic. Some varieties start to green in three days when kept under partially lighted storage conditions. Solanine in potatoes is not destroyed by cooking , baking or frying.

In the field, provide sufficient soil cover/hilling-up to the potato crop to prevent greening.

In-ground storage or delayed harvesting. Delayed harvesting is leaving the tubers on the ground after the vines have matured and died. This is done in the mountain trail specially in cool areas where drainage is good and the soil is light and loose. Tubers are kept after maturity in the field for up to three months and harvested as part of the wet season crop.

Some varieties are not suited to in-ground storage. Processing varieties wish shorter dormancy period is not suited to this type of storage. For processing purposes, in-ground storage is not recommended because it lowers the quality of tubers.

Source: DA