The importance of Seed Drying-for farmers, co-operatives, government institutions and seed companies
Seed drying and storage is probably the most important part of seed businesses. Whether it be farmer retained seed or high value hybrid seeds from a commercial seed company, dry storage of seed is acknowledged as vital to ensure high germination rates.
With the difficult, hot and humid climatic conditions in Asia it is very important for all parties in the agriculture to store seeds at the right seed moisture content (SMC). It is accepted that SMC, above all other controllable variables in seed storage, has the highest impact on successful seed germination and the resulting impacts on profitability.
Simple and Effective Drying and Storage of Seeds and Horticultural Products for Developing World Farmers
Delivering improved seeds to smallholder farmers in the developing world is an efficient and sustainable method of increasing crop yields and quality. Unlike fertilizers, pesticides and equipment, seeds can be produced locally for distribution to farmers or self-saved. Furthermore, improved varieties of horticultural crops often reduce dependence on synthetic pesticides, improve food safety, reduce pre- and post-harvest losses and fetch higher prices in the market. However, the benefits that developing world farmers accrue from improved varieties can depend on their local systems for seed drying and storage. Without proper storage conditions, seeds can rapidly lose viability, resulting in poor crop establishment, lack of uniformity, reduced yields and poor marketability. Farmers’ experience with poor seed performance lowers their incentive to invest in genetically improved seeds and stymies development of breeding and seed marketing systems for more productive horticultural varieties. On the other hand, farmer confidence in the quality of purchased seeds and in their ability to store they safely will strengthen local seed markets and increase yields and incomes.
Seed storage can be a major problem because the majority of the world’s poor countries are located in the tropics, where the combination of high temperature and high relative humidity causes rapid deterioration of seed quality. In South Asia, seeds harvested before or during the monsoon season need to be dried and stored until the next planting season. The relative humidity of the air for most of the period between harvest and planting often exceeds 75% and temperatures remain above 30°C, causing seeds to deteriorate rapidly. Seeds absorb water from the ambient air when they are stored in humid environments and lose water when stored in low relative humidity. Generally speaking, a seed’s longevity is reduced by approximately half for every 1% increase in seed moisture content (water content as a percent of fresh weight) or 5°C increase in temperature, and the effects are additive. Thus, seeds stored at 10% moisture content and 30°C will last only one-quarter as long as seeds stored at 9% moisture content and 25°C. This principle implies that seed storage life can be enhanced considerably by lowering both moisture and temperature. However, moisture content is the key factor that can be lowered for successful seed storage in tropical countries. Cold storage is expensive and difficult to maintain because electricity supplies are often inconsistent and unreliable. In addition, seeds that are dried to low moisture contents are more tolerant of storage at warm temperatures. However, even prolonged sun drying in high humidities cannot reduce seed moisture content to the levels low enough to assure long-term viability.
These problems can be overcome by drying seeds to low moisture contents using inexpensive hermetic containers and drying beads, a recently developed desiccant technology. Using drying beads, seeds can be quickly and efficiently dried to safe storage moisture contents, and storing seeds in hermetic containers not only maintains low moisture contents, it also prevents losses to rodents, insects and molds. Seed desiccant drying beads provide a simple, inexpensive and reusable method for seed drying in humid climates. In addition, the beads can also be used to dry herbs, vegetables, fruit, nuts, medicinal plants, or other horticultural products.