What is moisture migration?
Moisture migration (also known as top crusting) is the development of a layer of molded grain due to excessive moisture accumulation at or near the surface of the stored grain. Moisture migration is caused by the gradual movement of grain moisture by very slow moving convection air currents caused by wide grain temperature variations (grain temperature differentials) in a grain storage. The classic example of moisture migration typically occurs in bolted, corrugated steel bins where warm grain is stored in the summer, but cold fall and winter air temperatures cool a cylindrical volume of grain close to the sidewall and top surface. Air in cold outer grain near the sidewall is denser than warm air in the center of the grain. The cold air settles slowly to the bottom of the bin, gradually moves to the center, pushing the warmer, lighter density air upward through the warm center grain. As air warms, its relative humidity drops and moisture holding capacity increases. As warm, moisture la
