Very dry seed, such as in vaporproof packages, can be stored for 2-4 years in good non-conditioned storages, at reduced storage construction and operation costs and without loss of seed quality.
Seed Are Hygroscopic
Seed can be dried to very low moisture contents with special drying equipment. However, seed are hygroscopic, and will regain moisture from high atmospheric RH. Hybrid maize, for example, is normally dried to 11-13% moisture and packaged in cloth or other vapor-permeable bags. When seed at this moisture level are placed in vaporproof plastic bags and sealed, germination drops below acceptable levels within 4 months. In vaporproof packages, RH of the air inside the bag will come to equilibrium with moisture content of the seed, and will remain at that level. Thus, air in a moisture-vaporproof bag filled with maize seed at 13% moisture will equilibrate at about RH 65%; at this level, molds and insects can cause much damage. Also, seed respiration rate is high at this RH, and will generate additional moisture. In a sealed vaporproof bag, moisture content of the seed will control the RH of air inside the bag.