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close this bookRegenerative Agriculture Technologies for the Hill Farmers of Nepal: An Information Kit (IIRR, 1992, 210 p.)
close this folderCropping systems and post-harvest technologies
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View the documentLong- Term Storage of Seed Potatoes Using the Diffused Light Storage Principle

Long- Term Storage of Seed Potatoes Using the Diffused Light Storage Principle

WHY STORE SEED POTATOES?

Seed is the main cost of potato cultivation, accounting for almost 50% of the total cost. The potato seed is one of the major sources of potato diseases as well. Unavailability of good quality seed potatoes at the right time is another problem in potato cultivation. Therefore, if a potato grower is able to store his own seed potatoes in good condition for the following season, many problems can be overcome.

HOW TO STORE SEED POTATOES?

The best method of storing seed potatoes in the hills of Nepal should not require farmers to make major changes to their present storage practices. Any changes that have to be made should be low cost and easily constructed. Diffused-Light Storage (DLS) meets the criteria for storing seed potatoes in the hill region and it can be adapted to any existing on-farm storage.

WHAT IS THE DIFFUSED LIGHT STORAGE (DLS) PRINCIPLE?

DLS is based on the use of natural indirect light and good ventilation or air flow, instead of low temperature, to control excessive sprout growth and associated storage loss.

Provided that direct sunlight can be controlled, any kind of existing potato storage facilities can be converted into DLS. It is not necessary to build a new facility. There are many design options and any design used by farmers is good as long as the DLS-principle is adopted.

WHAT ARE THE ELEMENTS TO BE CONSIDERED IN THE DLS?

There are two basic elements of the DLS principle: light and ventilation.

1. Light

Light, which is the major element in DLS principle, should be indirect (no direct sunlight) but sufficient enough to be able to read in the storage place. Light checks the excessive white, thin sprout growth. Instead, it induces short, stout, coloured sprouts. Insufficient light intensity is indicated by the development of long, white sprouts which promote quick shrinkage in the tubers. Shrinkage of the tuber means energy loss. A shrivelled tuber is regarded as physiologically old and is not able to produce a good healthy plant. Therefore, potatoes must be arranged in the storage area so that each tuber receives sufficient indirect light.

2. Ventilation

Since the potato tuber is a living organism it requires sufficient air (especially oxygen) to breathe or respire. Respiration of the tubers produces heat inside the storage area. Heat speeds up the growth of sprouts which means the tuber is quickly using more energy, thus quickly becoming physiologically old. Good management of ventilation (air flow) helps to remove the heat generated by the respiration and to provide sufficient air for respiration.

SOME EXAMPLES OF LOW-COST DLS

Note: Any potato storage needs protection from rats. Use fine wire netting or any traditional method


Bamboo Basket (Perungu)

This basket, locally called PERUNGU, is traditionally used to store seed potatoes in the hills. It can be adapted to the DLS with minor adjustments, such as making layers inside (see figure). Seed potatoes in each layer should be filled up to half or two-third only, leaving the space for air and light. The perungu can be hung under the roof where sufficient indirect light and ventilation are available but should be protected from rain and wind. The size and shape of the basket can vary according to the needs of the farmers.


Wooden tray

This is another technique to store seed potatoes following the DLS principle. Normally, a tray size of 2 ft. long, 14.5 inches wide and 7 inches height has capacity to hold about 12kg (5 Dharni) of seed potatoes. (Rack size can vary according to the needs of the farmers). The trays can be stacked to save space and they are easy to move. The tray bottom should be made of slats with gaps between each slat (as shown in the figure) to provide air flow through the tray bottom. Each tray should be filled with potatoes up to 3-4 tubers height only. These seed trays can be placed inside or outside the house, wherever there is sufficient light and air flow.

Rack or Shelves inside or outside the house

Racks or shelves made of wood or bamboo can be made inside or outside the house on the Barandha to store seed potatoes. If shelves are made on the Barandha, they should be protected from rain water and wind. The potatoes should also be protected from rats with wire netting.


Rack or shelves inside or outside the house

Rustic Storage

Separate simple storage built from locally available materials can also be used to store large amounts of seed potatoes. A storage facility 6.5 ft. length, 2.5 ft. width and 7.5 ft. height with 5 shelves can hold 500 kg of seed potatoes. Shape and size can be altered according to the needs of the farmers and the amount of seed to be stored. However, there are certain points that need to be considered:

· Roof must be thatched, not made of tin as a tin roof heats the storage area.

· Roof must be wide enough to cover the full storage.

· Shelf height must be at least 1 ft. high.

· The lowest shelf should be more shall 1 ft. above the ground to prevent rain water splashing on the tubers.

· If possible, it should be built under the shade and on the north side of a tree.

· Fine wire net should be placed on the sides to protect the seed from insects, pests and thieves.


Rustic storage

Rotary Quern: An Appropriate Technology for Rural Communities

Rotary queen, known as janto in Nepali, is one of the manually-operated indigenous types of processing equipment. It is used for grinding foodgrains, especially cereals and millets into flour and splitting pulses into two halves.

TYPES OF ROTARY QUERN

Rotary querns found so far in Nepal can be classified as follows:

1. Non-adjustable rotary quern

· Portable rotary quern
· Non-portable rotary quern


Figure 1


Figure 2


Figure 3


Figure 4


Figure 5


Figure 6


Figure 7


Figure 8

2. Adjustable rotary quern non-adjustable

1. Non-Adjustable Rotary Quern

This type of rotary quern (Figs. 1 to 3) is commonly found in different parts of the Kingdom. It consists of two millstones. The upper millstone has a feeding hole at its center and a wooden handle near its periphery (Fig. 4 and 7). The lower millstone has a metallic pivot pin tightly affixed at its center (Fig. 5). It is either portable or non-portable.

The rotary quern found in the hilly areas of the far western development region of Nepal (Fig. 6) is of somewhat different design. The lower millstone is similar to the one described above (Fig. 5), but the upper millstone (Fig. 7) has a wooden rynd tightly fixed onto its undersurface (Figs. 7 and 8). The rynd, which can be seen when turned upside down, has a depression at its center (Fig. 8). It is generally portable.

2. Adjustable Rotary Quern

This non-portable type of rotary quern (Fig. '3) is more popular in Seti and Mahakali hills of the Far western Development Region of Nepal. It also consists of two millstones: the upper one is similar to the one illustrated above in Figs. 7 and 8. The lower millstone with an outlet is fixed on a stone masonry structure, similar to firewood cooking stove (Chullo), having an opening to receive wooden or stone wedges. It has a central hole tightly fitted with a wooden bush (Fig. 10). The bush is generally made of hard wood such as Sal (Shorea robusta) or Sisau (Dalbergia sissoo). A central pivot pin passing through the wooden bush and resting on three wooden or stone wedges supports the upper millstone trig. 11).

The gap or clearance between two millstones is adjusted by pulling or pushing the middle wedge. When the middle wedge is pushed inside, the upper millstone is raised and the gap between two millstones is increased and vice versa.


Figure 9


Figure 10


Figure 11

BENEFITS

The gap or opining between two millstones can be adjusted according to requirement.

The ground flour is discharged through an outlet to the receiver.

The grinding surfaces are smooth and not in contact with each other and, therefore, there is less wear and tear of stone surfaces causing less health hazard.