Sorghum growers who planted late and are now debating when to harvest high moisture crops have been offered some straightforward advice from a grain storage specialist - if possible, get organised and get it off.
Department of Agriculture and Fisheries (DAF) senior development agronomist (Postharvest Grain Protection), Philip Burrill, says late planted sorghum crops on the Darling Downs were presenting harvest concerns because their moisture content was well above the safe storage level of 13.5 per cent.
Mr Burrill says to avoid quality downgrades, it is critical growers have clear plans in place to implement aeration or grain drying strategies appropriate for moisture levels and with consideration for their equipment.
"There are growers who would like to harvest sorghum now, but it is sitting in the paddock at 15-20 per cent moisture content," he says.
"If they harvest sorghum with a grain temperature of 15-20°C and moisture content above 16 per cent and put it in a silo without aeration cooling fans running, it will rapidly 'self-heat' and develop moulds.
"But the simple fact is, the moisture content in the paddock is unlikely to decrease below 15 per cent moisture content quickly in the current conditions - so I would recommend getting the crop off."
Mr Burrill, who works on the GRDC's grain storage project, said he had received numerous calls from growers with high moisture concerns in recent weeks and his advice had been consistent.
Tips for storage
"The starting point for these growers is to accurately measure moisture content in the paddock, get organised in terms of what equipment they have access to, and get the crop off," Mr Burrill says.
"Options for managing high moisture grain depend on the equipment available, but it is important to understand it is very difficult to reliably reduce moisture content using standard small aeration cooling fans (output 2-4 L/s/t) designed for cooling grain, not drying.
"Growers should also to be aware that adding extra heat (4-6°C) to the air in front of small aeration fans (2-4L/s/t) is not reliable or safe.
"It typically ends up with over drying the grain in the bottom of the silo and depositing most of this removed moisture in the grain towards the top of the silo.
"The small aeration fans are however very useful when run continuously on silos that are temporarily holding wet grain. The continuous low volume airflow keeps grain cool.
"If choosing to use aeration drying in silos we require large output fans, providing total air flows of 15-25 L/s/t. Remember, only half or two thirds filling your silo increases the airflow rates in terms of L/s/t.
"For drying, fans are typically run for long run times of 18-22 hours per day for nine or more days, depending on ambient conditions."
Mr Burrill says in some situations adding additional heat (4-6°C) to this high airflow was worthwhile as it reduced ambient air humidity.
"In explanation, if you have 100 tonnes of sorghum in a silo at 15.5 per cent moisture content and wish to remove 2 per cent moisture content to bring it down to 13.5 per cent, you actually need to remove two tonnes of water," he says.
"In other words, 2000 litres of water and that is not going to happen reliably with standard low output cooling fans.
In most circumstances, Mr Burrill explained grain could be safely held for a few weeks at 14-16 per cent moisture content with small aeration cooling fans running continuously, delivering airflows of at least 2-4 litres per second per tonne.
"If you decide to hold high moisture content sorghum in your silo until you can put it through a drier, then aeration fans need to be used to keep the grain from getting hot and preventing mould and bin-burnt grain damage," he says.
"It is also important to do daily checks on silo fan operations, grain temperature and smell."
In summary, Mr Burrill says options for high moisture content sorghum were:
- grain dryer (batch or continuous flow)
- aeration drying in silos with high output fans (15-25 L/s/t)
- (for many growers), holding it in silos for a few weeks using the small aeration cooling fans (2-4L/s/t) prior to organising grain drying or blending.
Five tips for storing high moisture content sorghum:
- Run aeration fans continuously (24/7) after the first truck load goes into the silo. If possible, use silos with at least two aeration fans to assist with good air distribution through wet grain and trash. Clean the impeller on older aeration fans, as accumulated dust can significantly reduce airflow outputs. Ensure silo roof vents/top silo lid is open for good ventilation.
- High moisture sorghum (14-16 per cent) can be held safely while the small aerations are left running so grain does not get hot. Only turn small fans off briefly when outside air relative humidity remains above 85 per cent for more than 3-4 hours. With fog or mist, fans should be off.
- Have a grain temperature probe (Graintec Scientific) to check high moisture content sorghum temperature two to three times a day. Try to keep grain below 35°C. Augering the grain out of a silo into a truck - 'turning the grain' - will help with wet/warm grain in storage.
- Use a good quality grain moisture meter. Have it serviced and checked every few years.
- Always aim to dry or blend sorghum down to less than 13.5 per cent moisture content within 3-5 weeks.
GRDC Research Code: PRB00001