By Kim Stonehouse, PAg, Crops Extension Specialist, Tisdale
There are a number of factors that contribute to how well and how long grain can be stored before it is delivered to the buyer. For the most part, the combination of moisture content and grain temperature at the time the bin is filled and during storage, are the tell tale factors for grain safety. However, uncured/green kernels, excessive fine material and even the physical size of the storage container have the potential to impact how well grain stores. Monitoring is the only way to preserve grain quality.
It was not that long ago that the average bin size was 3,000 bushels or smaller. Today, bins larger than 5,000 bushels are common, with some as large as 50,000 bushels. Larger bins come with larger diameters. Bins with a smaller diameter tend to cool rapidly and have reduced potential for moisture migration to occur. While larger diameter bins can have a larger temperature differential that can remain unchanged for months, even though outside air temperatures have dropped significantly.
In bins where the grain has recorded an average safe storage moisture content there can be pockets of higher moisture due to immature kernels or simply a variation in conditions during harvest. The combination of large temperature differentials and high moisture pockets can lead to increased moisture migration creating problems with insects and moulds. You can learn more about insects and mould in stored grain on our website.
To avoid moisture migration, it is best to cool grain down to within 5 C of the outside air temperature as quickly as possible. This equalizes the temperature within the bin and can be accomplished through operation of aeration systems or moving grain. As outside temperatures decrease you may wish to cool again until the entire mass is close to 0 C for storage through the winter. The approximate temperature when insect activity stops is 10 C and cooler.
Another aspect to manage is the amount of fine and foreign material within the grain. Accumulations of these are often the start of storage problems. Managing this material can usually be accomplished at harvest time with the combine. However, if it can't, then management may involve the temporary removal of the core, where the fines are concentrated, or cleaning to reduce the unwanted material.
The key, of course, is monitoring. When grain temperatures are above 10 C, monitor on a weekly basis for changes in grain temperature. Pay particular attention to the larger bins or bins with marginally dry grain. Once the grain gets close to 0 C, monitoring can be reduced to monthly.
It is important to note the relationship between moisture levels and temperature for every crop being stored. As either moisture or temperature rises the length of time grain can be safely stored is reduced, but the actual relationships are slightly different for different crops. Safe storage charts for all crops can be viewed at the Canadian Grain Commission.
For more information, contact your local regional crops extension specialist or call the Agriculture Knowledge Centre at 1-866-457-2377.