Quality Seed from the Start
At the time of physiological seed maturity the germination and vigor of the seed is optimal and at its maximum. This is the time where our farmers are harvesting the seed. The seed is dried immediately after harvest to reach a moisture content of 12 to 13%. This puts the seed in the best position to be stored. A careful and soft handling during the seed processing is also your guarantee for a high quality product with a long shelf life. Nevertheless, seed is a living organism and aging of seeds starts right after harvest. The goal for storage should be to create conditions to slow the aging process.
Water Content and Temperature
Low moisture is more important than low temperature. You might experience problems if the seed is exposed to large differences in temperature. In that case air circulation can be initiated which does not only transport heat, but also moisture from seed to seed. This is possible because the difference in the temperature of warm seed and cold air condense water on the seed in the bag. The high moisture content accelerates the respiration of the seed and thereby the loss of energy.
Storage Condition Impact on Shelf Life
The temperature and humidity decides how long you can store the seed. Each seed has a built-in "shelf life meter" which is the potential time the seed can be stored.
Figure 1 - Deterioration of Seed Over Time
In Figure 1, Line A is the maximum period of seed shelf life, whereas Line B shows the effect of poor seed storage conditions in the warehouse. When conditions deteriorate, the seed germination will deteriorate accordingly. In the majority of cases, the germination will stay stable for a length of time before starting to decline.
Optimal Seed Storage Conditions
Generally, the colder and drier the surrounding environment, the better. The conditions to aim for are 30% relative humidity - or as low as possible and temperatures below 59°F (15°C). The aim is a temperature that is as consistent as possible. It is more important to maintain consistency, rather than maintaining a low temperature level, i.e. a range from 59 to 63°F (15 to 17°C) is far better than a range from 46 to 86°F (8 to 30°C). Darkness is a third rule of optimal seed storage. Light stimulate and support the germination process in the seeds and storage in darkness helps keeping the pre-germination processes in the seed at a low level.