Seed drying is transfer of moisture from the seed to the surrounding air.
This requires that the air be dryer than in equilibrium with seed moisture
content; i.e., at an RH below that which is in equilibrium with the seed
moisture content.
In the seed, drying is a 2-stage process (Figure 8.1):
1. Moisture moves from the seed surface into the surrounding air. If the
air has enough moisture-absorbing/holding capacity (i.e., RH lower
than is in equilibrium with moisture content of the seed surface), this
movement will be fairly rapid.
2. Moisture migrates from the center or inside of the seed to the surface.
Moisture movement from the inside to the surface is a relatively slow
process, varying with crop species.