|SPORE Bulletin of the CTA No. 62 (CTA Spore, 1996, 16 p.)|
It is estimated that 80% of all seed used by farmers in the tropics is derived from stocks held on-farm from previous seasons. If yields are to be sustained and even increased it is essential that seed storage is of a consistently high standard. Good quality seed is central to productive agriculture. Poor planting material results in poor field establishment and ultimately poor yields, irrespective of subsequent inputs.
Farmers choose to maintain their own seed stocks for a variety of reasons: the formal seed sector cannot, or does not, provide those varieties which farmers prize; the cost of buying fresh seed of 'improved' varieties on a regular basis is prohibitive; and because it appears that farmer selection of seed stocks often allows maintenance of yield levels under small-scale conditions. Because of the relatively small quantities involved and because sorting and planting are done by hand, farmers can select the largest seeds and those that are free of insect and mould attack, thereby ensuring plant-seeds with maximal vigour.
Despite this preponderance of farmer-held material, very little attention has been directed towards assisting farmers in maintaining their seed stocks in the best possible condition. Grain stored for food and grain held as seed face many of the same problems, such as insect and rodent infestation and mould attack, and hence many lessons learnt from experience with grain storage can be applied to the seed situation. However, food grain seeds are only useful if they remain viable. Since seeds are more sensitive to the effects of temperature and humidity than food grain stocks, they need to be handled with additional care in order to maintain their germination potential.
Agricultural development programmes that have a seed component often start with the premise that on-farm storage of seed must necessarily be inadequate and in need of improvement. These assumptions are rarely supported with survey or experimental data and their validity needs to be questioned.
With increasing appreciation of indigenous technical knowledge some studies have been undertaken to document farmer seed-saving practices. These studies show that farmers actively select planting material which they may then handle and treat in a different way to their food grain.
In Zimbabwe detailed qualitative studies show clearly that farmers have an extensive understanding of techniques which maximize seed performance. Such documentation of farmer practices is extremely useful but it is also important that some quantitative measure of success can be attributed to the various techniques. The organization Seeds of Survival working in central Ethiopia has, from preliminary data, established that germination levels of farm saved seed, from a variety of crops, was above 70% after six months storage in 85% of their samples. These findings are supported by a more extensive survey undertaken by staff of the Natural Resources Institute, UK, with collaborating national institutes in Ghana, Malawi and Tanzania. A total of 1,859 samples of five important crops were taken from farmers' seed stocks and assessed for germination potential just prior to planting. Maize, cowpeas and soya showed mean germination levels of above 75% whilst beans and groundnut were less consistent, though still good.
Until now, these quantitative studies have been carried out in countries or regions where the climate is conducive to successful seed storage, having significant dry seasons during which seeds can be conditioned before being placed in store. Whether or not farmer techniques are equally successful under hot humid conditions has yet to be established.
In terms of volume, farmer seed requirements are often small. This means that farmers can invest more time, effort and care into the maintenance of seed quality than would be practicable for food grain stocks. Often this simply means using a sealable container to prevent insect attack. Alternatively, farmers apply traditional or insecticidal admixtures to control or prevent insect infestation. For example, some farmers in northern Ghana mix their cowpea seeds with shea nut oil, which appears to have an excellent repellent effect on bean bruchids. Other farmers, who store their maize seeds as suspended cobs, cover them with plastic sheeting or gourd shards as rat guards.
These farmer initiatives are often very localized, despite being useful components of a seed storage strategy. Further studies would allow extension staff to decide which of these indigenous practices could usefully be more widely advertised. In addition, strategies that already have proven advantages but which are not universally adopted, should be promoted: for example, the selection of maize seed at harvest rather than just before the following planting season.
Is change necessary?
In the areas investigated it seems unlikely that at the farmer level, seed storage practices need to be drastically altered. Farmer techniques work sufficiently well and the only rationale for a radical change m storage practices would be if some major external change took place. This could include declining availability of traditional materials used as admixtures such as botanical insecticides because of over-cropping, unusual weather patterns, or the appearance of a novel pest against which traditional measures are ineffective (e.g. larger grain borer).
It is clear that in zones that have a climate suited to seed storage, farmers are frequently very accomplished at E maintaining the viability of their own seed stocks. The techniques employed, which may have evolved over considerable periods of time, are usually well adapted to the farming. system in which they are used. However, there is room for improvement to many of the current practices through farmers learning from each other.
Change can be brought about through awareness activities. This could take several forms, such as direct advice or through information exchanges, allowing farmers to become aware of techniques used successfully in other areas of the country. In this respect researchers and extension staff are most suited to act in the role of facilitators through the establishment of 'best practices' from among the range of techniques available, supporting farmer-based technologies and only offering totally new practices where the local systems can be shown to be failing.