Monitoring grain temperature and aerating grain

It is important to monitor grain temperature and to keep stored grain cool and dry by regular aeration or by turning it.

High moisture and warm temperatures in grain allow for the rapid growth of insects, fungi and the possible production of mycotoxins.

How temperature and moisture work

Grain is a very good insulator. When it is undisturbed, it holds temperature well. If warm grain is placed into storage and left undisturbed, convection currents develop and cause hot spots and moisture condensation. The greater the temperature differential (the difference between the temperature of the grain and the outside temperature), the stronger the convection currents. The stronger the convection, the greater the effect of heating and condensation on the grain. This is particularly evident when stored grain is not leveled and the grain bulk forms a peak.

In the bin:

• The surface of the grain bulk forms a peak.
• Grain at the surface and just below the surface has high moisture content.
• Warm grain is located in the centre of the grain bulk.

Arrows represent the convection currents.

• Cold air flows down from the surface of the grain, along the interior of the bin wall. The flow of cold air surrounds the warm grain.
• At the bottom of the grain bulk the cold air is drawn to the centre of the grain by an upward flow of warmer air. The upward flow is a convection current created at the centre of the grain bulk.
• As the cold air is drawn to the centre of the grain, it warms up and flows up to the surface of the grain bulk where there is moist grain.
• The warm air is cooled as it reaches the surface, condenses, and the cycle is repeated.