Almekinders, C.J.M.

Louwaars, N.P.

English

Wageningen Yield 

96 
objectives in local seed management, which may benefit from various methods of 
maintenance selection derived from the formal seed system. The resources and 
knowledge of farmers, and their priorities with regard to their varieties largely 
determine which methods are most appropriate for their conditions. 
 
 
 
2.2 Supporting farmers’ practices in seed processing and 
storage*
 
Niels P. Louwaars and Conny Almekinders
 
Post harvest operations and storage methods have strong effects on seed quality. This 
section introduces general aspects of these operations, such as handling, seed drying, 
cleaning, treatment and the effects of temperature, moisture, and insects on the 
potential loss of seed quality during seed storage. These aspects can be taken into 
account when assessing and seeking ways to support farmers’ methods of seed 
processing and storage. 
 
Harvesting  
Harvesting should be well timed to allow quick drying of the seed, and to avoid 
important losses due to shattering or field infestation of storage insects (e.g. weevils in 
maize, bruchids in faba bean). Farmers often delay harvesting because of the peak 
labour needs at the end of the season, and because drying of the crop on the plants 
reduces the need for drying floors. Harvesting and threshing have to be done with 
much care to avoid damaging the seed. Threshing when the seed is over-dried may 
cause the seed to crack, while threshing wet seed may cause (internal) damage and 
create subsequent germination and vigour problems.  
 
Processing 
Processing is the first post-harvest activity in farmers’ seed management. It includes 
activities such as handling (transporting/receiving), seed drying, cleaning and treating.  
 
Drying 
Seed should be dried quickly, but high temperatures can damage the seed. Sun-drying 
can normally be completed in a few days. For some crops, such as maize or sesame, 
special racks or cribs are used to improve the ventilation and speed up drying. If seed 
is dried on the floor, regular turning will improve the balanced drying of the seed lot 
and avoid mould growth at the bottom of the layer. In humid climates, seed drying 
can be a serious problem. If harvesting cannot be done during a dry season, small 
scale wood-fuelled dryers can be used. These require a considerable investment and 
* This section is adapted from Almekinders, C.J.M. and N.P. Louwaars, 1999. Farmers’ seed 
production. New approaches and practices. London, Intermediate Technology Publications: 
pp. 112-118. 
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experience has to be obtained to avoid over-heating of the seed. The effect of high 
temperature is most damaging when the moisture content of the seed is high.  
 
Cleaning 
Seed cleaning has a dual purpose: it removes non-crop seed materials from the 
harvested material, such as straw, stones and weed seeds, thus reducing the bulk to be 
stored; and it also selects the seeds on the basis of physical characteristics such as size, 
shape, density and colour, thus removing small and shrivelled seeds and improving the 
seed quality. 
For most crops, seed cleaning is no different to the cleaning of food grain for 
consumption, so that local methods for cleaning food grain are well suited for seed 
cleaning. Such methods include winnowing, sieving and hand-picking. Winnowing 
removes the light particles like straw and dust, and it can be used to remove seeds 
with a low density (low weight per volume: empty or ‘soft’ seeds). Sieving selects the 
seed on the basis of shape and size. Hand-picking is used to remove diseased and 
discoloured seeds. See Box 2.5 for an example of how seed selection and cleaning may 
positively affect on-farm seed production. 
 
Box 2.5 Improving on-farm seed production of millets  
 
An NGO operating in West Africa collected some samples of millet during a diagnostic 
survey in a low rainfall area. Unlike modern varieties, the traditional millet varieties were 
well adapted to the length of the growing season and the farmers’ culinary preferences, but 
plant stands in the field were very variable. The collected samples were analysed. The 
proportion of small and damaged seeds was considerable. After removing these seeds, two 
samples of 200 seeds from each collected seed lot were germinated: one sample using a test 
called the ‘rolled towel test’, and the other using a calabash containing moist sand. 
Results of the analysis were discussed with the farmers from whom the seed had 
been collected. Farmers showed an interest in carrying out the simple seed testing in a 
calabash filled with moist sand. Individual farmers and NGO technicians also decided to 
mark out a 20 x 20 m seed plot in the centre of their field where they thinned the millet to 
one plant per mound and removed diseased plants. At harvest they used the criteria of 
colour and vigour to select plants for seed which were disease free, high tillering, and had 
many medium to large heads. Utilizing the harvested seed and the sieving method, farmers 
realized a 30% yield increase in the following year. Other farmers were informed through 
group meetings where the individual farmers were invited to relate their experiences. In 
1992, 50 farmers in 5 villages produced 850 kg of seed. 
 
When (women) farmers pick their bean seeds just before planting, they can easily 
remove discolored seed due to disease infection. The chief limitation of hand-sorting 
seeds is, however, the time it takes. Relatively small seed-cleaning machines (0.5 t/hr) 
are available, but their cost and their dependence on electricity are prohibitive in many 
cases, and such an investment should be considered very carefully for the relatively 
small quantities and time period involved (compared to grain).  
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Treatment 
After cleaning, the seed may or may not be treated, depending on the local need to 
control plant pests. Chemical seed treatment has become routine practice for many 
crop seeds in formal seed systems, and increasingly also in farmers’ seed production, 
and is seen as offering the cheapest, safest and most efficient form of plant protection. 
Farmers often use chemicals in powder form, first diluted in water and then mixed 
with seed manually on tarpaulins using shovels. However, the main constraints for 
seed treatment include problems related to: availability; methods and rates of 
application; safety precautions; lack of adequate equipment and knowledge. Good 
extension programmes for seed treatment would help farmers to use chemical 
treatments more effectively, targeting the organisms and reducing costs and 
environmental pollution. It would also be helpful to provide hand operated or mobile 
seed cleaners, and to make sure that seed is bagged in clean bags without insects or 
leftover seeds from the previous harvest. To avoid mistakes, seed bags must be 
labelled. 
 
Storage 
The main enemies in seed storage are high temperature and moisture, which affect the 
maintenance of seed quality in storage. Table 2.1 gives approximate periods that seeds 
of a number of crops can be stored under given seed moisture conditions. 
Additionally, high temperature and moisture favour the development of insects, 
bacteria and fungi. Table 2.1 can be read as follows. When pearl millet seed with a 
germination percentage (viability) of 90% is stored during a rainy season (high 
humidity of the air, e.g. 75% and 24ûC) the viability will drop to 70% within two 
months. If however, the seeds can be packed in a moisture-proof container after 
thorough drying just after harvesting, resulting in a humidity of 45% inside the bag, 
they will still be viable after 13 months of storage (first column). A similar result could 
also be obtained by reducing the storage temperature to 8ûC (but this is impractical 
under farmers’ conditions). 
Storage structures and practices should also protect the seed against damage by 
rodents. Storage structures for food grain are often designed for the same purpose. 
Temperature can be difficult to manipulate, beyond such measures as avoiding stored 
seed being exposed to direct sunlight or to heat under a corrugated iron roof. 
Traditional storage structures, such as those using mud walls or underground spaces, 
are often well-designed and provide efficient isolation to keep temperatures 
moderately low.  
Ideally, airtight containers are used to store well-dried seed. This is feasible for 
small quantities of vegetable seeds, but not for bulky field crop seeds. For vegetables, 
various glass jars are used, such as soda bottles sealed with candle wax. In some 
countries, 50 kg bags of laminated polythene/aluminium foil are available; in other 
areas, multi-layer polythene-lined oil drums are used. Airtight containers also solve 
possible insect problems because the insects suffocate as soon as the oxygen in the 
container is used up. This process can be speeded up by making sure the containers 
are well filled, or by filling any remaining space with inert materials such as sand or 
ashes to reduce the volume of air and restrict the movement of insects. Projects in 
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which small low-cost aluminium tanks were designed and locally produced have 
successfully improved maize seed storage in Central America and other places. 
 
Table 2.1 Storage ability of different crop seeds 
 
Length of safe storage at 24oC 
(months)1 
Maximum temperature for 
one year storage (oC) Crop 
RH=45% RH=75% RH=45% RH=75% 
Barley 19 2 27 10 
Pearl millet 13 2 24 8 
Rice 13 3 24 11 
Wheat 6 1 20 0 
Rape 28 4 29 15 
Pea 37 3 32 15 
Bean 67 12 37 15 
Cowpea 39 4 33 14 
Broad bean 70 15 36 25 
Groundnut 11 1 23 - 
Soybean 17 2 26 10 
Cabbage 23 4 30 17 
Onion 13 1 23 10 
Lettuce 35 3 30 15 
1 Calculated with the ‘Seedlife’ programme, developed by Plant Research 
International, (Wageningen, the Netherlands). The following conditions are 
assumed: germination before storage 90%, germination after storage 70%, no 
insect damage. 
 
It is extremely important that seed in airtight containers is dried very well before the 
container is closed, especially when the storage season is warm and humid. Some 
respiration will occur, thus increasing the relative humidity (RH) in the container. This 
problem can be reduced by placing layers of fresh charcoal in the container, separated 
from the seed by newspapers. The charcoal absorbs the humidity. In most cases 
however, seeds have to be stored in ordinary gunny bags or in bulk. In this case, good 
storage conditions are very important: cool, dry and free from insects or rodents.  
The storage of the seed also needs to be safe from theft, and from fire and 
other calamities. Grain stores are generally rather well protected from rain and rodents 
(e.g. setting rat traps at the poles under the store). Hollowed-out gourds are 
sometimes inverted over hanging seed ears to provide protection against rodents. In 
Mali, small amounts of cucurbit seed are protected by mixing them with cattle dung or 
mud and plastering the cake formed onto a mud wall under a roof.  
Seed is also often stored in the house for even better protection and for 
safety. An exceptional storage method is the hidden underground store used in some 
parts of Ethiopia and the Middle East. These stores have proven safe even after 
displacement of farmers during civil unrest. Storing seed ears in the kitchen hanging in 
the smoke of the fire is not only a safe place, but also keeps the seed dry and reduces 
insect and disease damage.  
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Generally, farmers have local knowledge of treatments for protecting seed 
during storage using ash, sand and plant extracts, for example. Mixing beans with ash 
is reported to reduce damage by bruchids and other insects. The ash damages the 
cuticle of the insects, causing them to dehydrate. Ash should be added in sufficient 
quantities: 25-50% by volume is recommended, and the addition of lime and 
diatomaceous soils improves the effectiveness of the protection.31 Vegetable oils, such 
as for example soya oil, can be used as a dressing to reduce insect damage. Damage by 
bruchid and Acanthoscelides is reduced by mixing 5-10 ml of vegetable oil to 1 kg of 
beans.31 In Northern Ghana cowpeas are mixed with shea butter oil and left in the sun 
as protection against bruchids.32 
Various plants and plant extracts are used in different parts of the world, such 
as crushed seeds or leaves of neem, eucalyptus or lantana. It must be borne in mind 
however, that natural substances may be as toxic as chemical biocides and should also 
be treated with care. For insect control, application of chemicals can be very effective.  
 
 
 
2.3 Community seed banks: experiences from Tigray in 
Ethiopia
 
Trygve Berg and Fetien Abay
 
Community Seed Banks (CSBs) were set up in Tigray in northern Ethiopia during 
times of war. CSBs were first developed in 1988 as a response to hardship and famine, 
and from 1991 they were seen as instruments of post war recovery. During the 1990s, 
with the situation gradually returning to normal, government services entered 
agricultural development. They provided farmers with ‘packages’ of improved seeds 
and fertilizers. Since then, government seed supply services have changed and the 
influence of the private seed sector has grown.  
Traditional seed selection is in decline in many communities in Ethiopia, and 
not all farmers have physical or economic access to certified seed. Therefore, 
alternative approach towards seed supply offered by the CSB deserves careful 
examination.* In this section, we aim to respond to a number of questions aimed at 
assessing the impact of CSBs on the informal seed system. Our leading questions are: 
Is it possible through CSBs to revive and strengthen farmers’ culture of seed 
selection? Could CSBs and a revived culture help to improve the quality of the seeds 
that farmers use? And could CSBs contribute to seed security and to improving the 
livelihood of the poorer households?  
 
The beginning of seed banks: a community response 
Collaboration and community action are common features of adaptation to crisis, 
including famine survival strategies. The idea of organizing seed banks emerged from 
* See also Section 2.4 by Pitambar Shrestha and colleagues on community seed banks in Nepal. 


Supporting farmers' practices in seed processing and storage

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