Type of aeration and silo design is best for your operation?

Which type of aeration and silo floor design is best for your operation?

The harvest is the heart of any farming operation – but how efficiently are you managing your harvest once it leaves the field? No amount of maintenance or crop management is going to prevent the outcome of poor grain storage practises. That is why it is crucial for farmers to carefully assess their grain management solutions, and to choose the aeration type and silo floor design best suited to their operation. If there is a gap in knowledge when it comes to this area, it is always best to consult with an agricultural expert to ensure that the right choice is made.


Fully perforated floor

An important factor in the efficacy of your aeration system, is the flooring of your bin. A fully perforated floor is the top choice when it comes to natural air drying, as it is able to provide the maximum open area and the least possible airflow resistance. This design makes use of perforations that span the entire floor area. These perforations, whether round or louvered, provide the most evenly distributed airflow through the grain. The consistent airflow provided by this floor type minimises the risk of heat pockets and other risks developing – making it the perfect choice for natural air drying.


When designing a flooring systexm, the size and type of perforations will need to be assessed to ensure that the most effective choice is made, based on the grain being stored. Be sure that your grain is not too close in shape or size to the perforation, so that the blocking of airflow does not occur. Also ensure that there is at least one square metre of open area for each 1000 cubic metre per minute (cmm) inside of the bin.


In-floor tunnel systems

These systems consist of concrete flooring with partial perforation areas, and include configurations such as the tube or half round duct systems. Their lack of louvred/perforated surface area, and limited pattern layout, greatly limits the airflow within the grain – making the cooling/conditioning of grain possible, but eliminating the use of the system for natural air drying.


Natural Air Drying/Low Temperature Drying

The process of in-bin drying can utilise both natural air, or low temperature air to dry grain in bins. This method of drying takes place over a period of 3 – 6 weeks, and carries a lower operational cost than batch and continuous flow drying, but will be less effective in areas where grain produced has a higher moisture content. This needs to be carefully assessed, as natural air-drying produces a high quality of dried grain, with higher test weight and germination, as well as lower breakage susceptibility than grain dried with high-temperature drier. Ruling out natural air drying unnecessary may result in loss of quality, and profit. When opting for natural air drying, a perforated floor, and a drying fan that is able to push 0.5 – 1.0 cmm/bu (cubic metres of air per minute per bushel of grain) as well as sufficient top vents to provide 1 square foot of vent area per 1000 cfm of airflow is strongly recommended. A shorter bin is also recommended (less than 5 m) as a drying zone of about 600 cm forms at the bottom of the bin, and slowly moves its way up, and grain at the top of the bin will remain at its initial moisture content until the drying zone makes its way through the entire bin. If the bin is too high, or the fan installed is not large enough to produce sufficient airflow, the top grain will spoil. Airflow and power requirements will need to be carefully calculated depending on the initial moisture content of the grain, as well as the weather conditions during drying.


Recommended airflow for natural-air and low-temperature drying

Moisture Content (% wet basis)

Minimum Airflow (cfm/bu)







Weather conditions will need to be assessed to determine if adding a low-temperature drying fan to your storage bin is necessary. This type of fan heats the air by a mere 2.2°C, but this addition reduces the relative humidity greatly, by between 3 – 10%. This slight increase in temperate and the resulting humidity reduction causes grain to dry by an additional 0.75 – 1.0%.


Temperature (°C)

Relative humidity (%)


40 60



8.5 11.7 14.6



8.2 11.3 14.2



7.9 11.0 13.7



7.7 10.7 13.3


25 7.5 10.4 13.0



That said, due to average weather conditions being acceptable for air drying grain, it is often times better for fans to be operated continuously, using air that is not heated (except by the fan) to avoid over-drying. If you are not sure of the impact that adding heat to your drying bins will have on your grain quality, it is best to consult with an expert.


Batch and Continuous flow drying

This drying method is best when working with large capacities of wheat. With high airflow rates, grain can be dried in a couple of days, or in some cases, few hours when using a high-temperature drying system. When using this method of drying careful consideration is needed, taking grain type, the temperatures used, and other key factors to ensure that loss of quality and germination is not encountered.


A clear fact when it comes to grain storage is that the higher the storage temperature, and the higher the grain moisture content – the shorter the safe storage duration will be. With that in mind, ensure that you have a careful strategy in place for your grain storage to avoid spoilage. If you are unsure what is best for your operation, it is always safer to consult an expert advisor who can help you to calculate your equilibrium moisture content, drying costs, and return on your investment. Contact SBS® Agri today on 0861 SBS AGRI to have our agriculture business consultants help determine what is best for you.