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.