A variety of seeds are commonly stored for consumption or processing in future. The primary concern in such storage is to protect the seed from damage by fire, water, insects and rodents. However, seeds must also be preserved for sowing at a later date or for genetic experiments. When stored for such purposes, the seeds must also be protected from loss in germination potential.
Importance of Seed drying and storage
Due to improper drying and storage conditions, seeds suffer from major retarding effects. These are:
- Loss of viability.
- Discoloration.
- Toxin production.
- Growth of fungus.
Therefore, seed conservation through efficient processing and storage becomes factor of prime importance. Proper drying limits the subsequent rate of seed deterioration during long term storage.
Three important factors determine the shelf-life of seeds:
- Storage temperature
- Relative humidity of surrounding air
- Moisture content of the seed during storage
Purpose of Seed Storage
After the seeds are dried, the next phase is their safe storage. Safe storage of seeds is important for a variety of reasons. Obviously, seeds must be preserved for use as human and animal food, and for planting. Seed viability must also be protected for various uses (germplasm protection) by the plant scientist who maintains a permanent reservoir of seed stock by establishing a seed bank.
Seed storage is the maintenance of high seed germination and vigour from harvest until planting. The purpose of seed storage is to maintain the seed in good physical and physiological condition from the time they are harvested until the time they are planted. Seeds have to be stored, of course, because there is usually a period of time between harvest and planting. During this period, the seeds have to be kept somewhere. While the time interval between harvest and planting is the basic reason for storing seeds.
Seed suppliers are not always able to market all the seeds they produce during the following planting season. In many cases, the unsold seeds are ‘carried over’ in storage for marketing during the second planting season after harvest. Problems arise in connection with carryover storage of seeds because some varieties and lots of seeds do not carryover very well.
Optimal Seed Storage conditions
Storage conditions depend on projected use of seed. Seed Storage has certain requirements which include protection from water, contamination, rodents, fungi etc. Additionally, controlling relative humidity and seed storage temperature is vital. The two are interrelated. Interestingly, for short term storage, their relationship can be expressed by a simple rule of thumb. Storage temperature (in °F) plus relative humidity should total 100.
For achieving the controlled air requirement, refrigeration, offers a direct, simple and economic solution to control both temperature and relative humidity to the specified level.
Seed Drying Conditions
The amount of moisture present in the seeds affects both the quality and storability of the seeds during long term storage. Generally, drying seeds to 4-6% moisture content on wet basis decelerates the rate of seed deterioration exorbitantly.
Seed Drying using the Dehumidification principle
Seeds cannot be dried by exposing them to heated air as elevated temperatures will destroy their germination potential. The alternative applied is to release the moisture from the product to the surrounding air. The dryer by maintaining the air at a lower moisture level can increase the drying rate. Moreover it removes the variability of weather as a factor in a drying operation.