- High-moisture grain is not safe to store without aeration or drying, but can be temporarily held in silos with aeration cooling before being dried or blended
- It’s important to regularly monitor stored grain temperatures to avoid spoilage
- Do not store high moisture grain infected with fungi or moulds
With wet and cool weather continuing to complicate harvest, growers may be thinking about their options for managing higher moisture grain (either this year or in future seasons).
So, what are the key things to consider?
The influence of temperature
When grain is stored at harvest temperatures of 25–30°C and a moisture content greater than 13–14%, mould and insect growth can become problematic. Moist, warm grain can also overheat, causing damage to the grain (bin burn) and reducing grain quality (including germination and vigour in seed kept for sowing).
It’s important to monitor the temperatures of stored grain regularly (for smaller storages, use a grain moisture probe; for larger silos, consider sensors that deliver data to your phone).
During summer and early autumn, target grain temperatures of 18–23°C. For winter and spring, aim for temperatures less than 15°C.
Managing higher moisture grain
There are a few options for storing wet grain for those with suitable storage facilities, however those without grain drying or blending facilities will need to delay harvest until moisture meets receival standards.
Hold short-term with aeration cooling:
Aeration cooling involves pumping air through the storage so that the grain eventually reaches the temperature and moisture of air traveling past. Aeration cooling provides a way for grain harvested slightly over moisture (14-15%) to be stored for up to three–four weeks before it is dried or blended.
For aeration cooling ensure;
- Airflow 2-4litres of air/second/tonne (L/s/t)
- Air is evenly distributed through the silo and ducting or vents allows hot/moist air to escape
- Cooling fans run continuously if grain is above 12.5% moisture and ambient relative humidity is below 85% (for information on when to run fans visit https://storedgrain.com.au/wp-content/uploads/2013/07/GSFS-7_HighMoistureGrain_2013_LR_Final.pdf)
- Consider partially filling the silo to reduce grain depth and increase air flow
- Temperature is monitored daily, especially in the first 24-48 hours (if temperature is high in middle of silo, grain will need to be turned)
Aeration cooling is only suitable if grain is not mould or disease affected. Small seeds, such as lentils, will reduce the aeration fan capacity as there is less space for air to flow between grains.
Aeration cooling systems can be retro-fitted to existing silos, or ordered when commissioning new storage.
Mixing slightly over-moist grain with drier loads will lead to a lower average moisture when properly blended. Blending is suitable for grain up to 13.5% moisture content (providing suitable infrastructure is available).
- Layered blending may be possible if grain moisture is only slightly high (ensure even layers) and the blended load should be stored in a unit with aeration cooling to help redistribute moisture evenly
- If aeration cooling isn’t available, grain must be evenly distributed in storage.
Aeration drying is usually done in a purpose-built drying silo or a partly filled silo with high-capacity aeration fans. It involves moving large volumes of air to force a drying front through the grain, which slowly removes moisture (Note: this is different to aeration cooling systems).
Successful aeration drying requires;
- High airflows (15-25 L/s/t)
- Adequate ducting and ventilation
- Long run-time (24hrs/day for first week at least)
- Daily monitoring
- Correct management of run times to avoid damaging grain
Grain should be returned to aeration cooling after drying.
Continuous flow drying with heat
In continuous flow drying, grain is moved through a dryer which uses a high volume of heated air to pass through a continual flow of grain. It is not recommended for grain that is going to be used for seed (heat will affect germination and vigour).
When using a continuous flow dryer, it’s important to:
- Always follow manufacturer’s instructions to avoid overheating grain
- Return grain to aeration cooling after drying