Managing moisture in stored grain

Grain growers are using aeration fans on their silos to push air through stored grain to improve harvest flexibility and increase marketing options.

Grain at typical harvest temperatures of 25–30°C and moisture content greater than 13–14 per cent provides ideal conditions for mould and insect growth.

Aeration cooling (2-4 litres of air per second per tonne) makes grain moisture more uniform and reduces grain temperature to create an unattractive environment for insect pests.

Aeration drying (requiring more than 15l/s/t) can be used to dry grain, allowing greater tolerance of moisture at harvest.

But aeration drying makes the task of storing grain on farm even more challenging.

Aeration drying requires a specifically-designed system and is a much slower process than aeration cooling.

There are a number of ways to deal with high-moisture grain — the key is to act quickly and effectively.

Grain that is above the standard safe storage moisture content of 12.5% can be managed in a number of ways:

  •         Blending — grain over 12% moisture content is mixed with low-moisture grain then aerated.
  •         Aeration cooling — grain of moderate moisture, up to 15% moisture content, can be held for a short term under aeration cooling until drying equipment is available.
  •         Aeration drying — large volumes of air force a drying front through the grain in storage and slowly remove moisture. Supplementary heating can be carefully added with subsequent cooling using ambient air to cool the grain.
  •         Continuous flow drying — grain is transferred through a dryer, which uses a high volume of heated air to pass through the continual flow of grain.
  •         Batch drying — usually a transportable trailer drying 10–20t of grain at a time with a high volume of heated air to pass through the grain and out through perforated walls.

For more information on managing high-moisture grain, see GrowNotes Grain storage Section 7 Managing high-moisture grain, download the free GRDC fact sheet Dealing with high-moisture grain or listen to grain storage consultant Phillip Burrill’s useful tips on cooling aeration in this GCTV5: Aeration Drying – getting it right video.

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