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4. Farm and village level storage
4.1
Farm storage methods
4.2
Village level storage
4.3
Drying
4.4 Pest control on farm level
4.5
Further literature
Farmers traditionally store their grain in an unthreshed state. This is first because they often do not have the time to thresh the grain after harvesting, and secondly because they rely on the lower susceptibility of grain stored in husks to infestation from pests. The storage period on farm level generally lasts 6 to 1 2 months.
After harvesting, the grain is kept in a variety of different traditional storage containers which are in general perfectly adapted to the existing social, economic and climatic conditions and require only locally available materials. Three basic forms of small farm storage can be distinguished: open, semiopen and closed storage systems.
4.1.1 Open Storage Systems
In unfavourable hot and humid climatic conditions almost only open storage systems are used because the stored produce is still moist when it is put into storage. Platforms resting on wooden stakes are very widespread, on which cobs or panicles are stacked in layers. A straw roof affords protection against the rain.
Crops are also occasionally to be found hung up in frames or under the roof of houses. In the latter case, the fire underneath is used to dry them and to repel insects.
Open systems are generally very simple constructions where storage hygiene is difficult to practise
Advantages:
Drawbacks:
4.1.2 Semi-Open Storage Systems
Semi-open storage structures are particularly widespread in semiarid regions. They include containers made of woven twigs or straw as well as wooden frames with a straw mat on which the commodities are placed. Crops are generally stored in an unthreshed state, i.e. in cobs or panicles. Contact to the ground is prevented by means of stone foundations so that ground moisture cannot penetrate into the store. A straw roof affords protection against the rain.
Semi-open storage systems give better protection against weather conditions as open ones but reduce aeration and provide no obstacle for pest entry.
4.1.3 Closed Storage Systems
In arid regions, for the storage of sorghum, millet, pulses, paddy and peanuts, use is made primarily of closed storage containers made of mud, often mixed with chopped straw, which is known as "banco". The crops are generally stored in a threshed state. Problems with moisture or condensation are virtually unknown due to the low moisture content of the stored produce and the excellent insulation capacity of the mud used. These "banco" containers are to be found in all shapes and sizes. They are usually closed with a lid and protected against rain with a straw roof Large stones serve as a foundation and prevent any ground moisture from entering.
Calabashes, clay pots, wooden containers and clean oil drums are also in use and have often proved to be of good effect in small farm storage, especially for seeds and grain legumes.
In closed storage systems, condensation may occur especially in metal containers (e g. oil drums). Particular attention must be paid to maintaining constant storage temperatures by means of providing shade.
Advantages of closed storage structures:
Drawbacks:
Small farm-storage in underground pits is a special form of a closed storage system and has been repeatedly referred to in the literature as a promising method of storing grain. There are no doubts as to the advantages of such a largely airtight and cool form of storage not affected by any fluctuations in temperature.
If the pit is kept satisfactorily air and watertight the development of insects and mites as well as the growth of moulds can be reduced to a minimum. A suitable site must be chosen with the right type of soil. The entry of both ground and rain water must be prevented and the pit walls should be waterproof in areas with a sufficient dry climate underground stores are a recommendable alternative to the known small farm storage systems.
Food storage on village level in form of cereal banks has developed since the beginning of the seventies, particularly in Africa Cereal banks are managed by cooperatives or groups of farmers. They try to assure food security to the village community and to provide farmers with the opportunity to sell their surplus when they can obtain better prices.
These stores with a capacity of between 10 and 50 t often have constructional features which do not allow low-loss storage. Essentially the same principles as for the construction of large stores apply for building the smaller cereal banks (see section 5.1. I).
The GTZ Post-harvest Project has developed an improved type of a village store with a capacity of around 25 t, which can be extended as required. The walls are made of cement bricks, the domed roof of reinforced concrete.
The advantages of this type of store ale as follows:
Another type of construction which can be recommended for storage on a village community level is the use of airdried mud bricks. The walls are plastered with cement mortar. A suitable supporting structure enables the roof to be built of bitumen and mud up to a certain store capacity.
4.3.1 Sun Drying
Products must be dried to the safe moisture content before storage. This is particularly difficult in humid areas. The traditional methods make use of sun and wind or fire. The produce is placed on the ground, on platforms or on special drying racks. When drying in the sun directly on the ground, the produce must be protected from absorbing any soil moisture by using sheets or mats. The thickness of the layer of cobs, panicles, pods or grains must not exceed 5 cm in order to ensure good and even aeration The produce must be turned over regularly in order to dry it evenly.
In the evening, the produce must be put in a pile and covered.
On special drying places there is always the risk of pest contamination. It is thus absolutely essential to keep these places clean.
Heat damage may result from too much exposure to the sun radiation or when drying the produce above a fire (grains cracking, losses in germination power).
Care should be taken not to exceed the following maximum drying temperatures:
Beans: 35°C
Cereal seeds: 43°C
Cereals for consumption: 60°C
4.3.2 Cribs
A drying frame or crib, developed in Nigeria, has proved to be of exceptional value, particularly in drying maize cobs. The crib consists of a wooden or bamboo frame with walls made of wire mesh or wooden slats and a thatch roof it has a maximum width of 60 80 cm. This guarantees good aeration and drying, even in humid regions. The cobs are left in the crib for up to 3 months, depending on weather conditions, and thereafter put into the store. In some areas these cribs also serve as stores.
4.3.3 Solar dryers
Solar dryers are based on the principle of conducting air heated by a sun collector through the produce.
The advantages of solar dryers as compared to the traditional method of sun drying in the open air are:
The drawbacks are:
Unfortunately, solar dryers have not yet been established to the desired extent due to socio-cultural, technical and financial reasons. In addition, cloudy skies at the time when the crops are harvested in many regions limit the use of solar energy.
The technical problem of creating a sufficiently strong current of air in the dryers has not yet been fully solved. This air stream is necessary in order to evacuate the saturated air after having passed through the produce. Otherwise condensation or mould can occur. Simple solar systems which take into account the demands of the users are nonetheless likely to gain in importance in the future.
4.3.4 Bush Dryers
Bush dryers are constructions built in the form of a tunnel made of mud or metal drums, and through which hot air is conducted with the aid of an open fire. The produce, spread out on a platform positioned above the tunnel, is dried by heat radiation. Adequate drying can, however, only take place if the produce is spread out in layers no thicker than 2 3 cm. As there is generally no possibility of regulating the heat, overheating and damage to the produce may easily result.
Bush dryers are easy to build and very effective. They are run on wood or charcoal as well as crop remainders. The use of bush dryers is, however, not undisputed because of the resources needed to fuel them.
