Proper grain storage to prevent spoilage and grain losses is highly dependent on an effective grain storage system. Storage structures must be designed and maintained to protect grain from weather, bird, animal, insect, and mite and mold damage. Grain that is to be stored for any length of time must be kept uniformly cool and dry.
Moisture content and temperature are the main factors that determine the length of time that grain can be safely stored. Enzyme activity and microbial growth will increase dramatically when moisture content in the storage bin rises above 70%, thus causing damp grain stored at warm temperatures to rapidly spoil.
Wheat that is less than 14.6% moisture is considered dry enough for safe storage and can be sold without a price discount. Wheat between 14.6 and 17.0% moisture is graded tough and must be dried to 14.6% to be stored for the long term. Wheat over 17% moisture will deteriorate quickly and can only be stored with extreme care.
The safe storage time of grain decreases as temperatures increase. The uniformity of grain temperatures within a storage bin can also affect the safe storage time of grain. Condensation occurs when moist, warm air comes in contact with cold objects. Temperature differences within grain bins cause moisture to migrate from warm to colder areas and conditions may become favourable for rapid grain spoilage if air movement is insufficient to remove the moist air from the bin. These conditions are most likely to occur when grain is stored in large (+3000 bushel) poorly ventilated bins. Differences in grain temperature and the outside air can also create high moisture areas within a bin.
Cooling the grain must be given first priority when dealing with high moisture grain in storage or the damp grain will heat quickly and spoilage will start. Aeration has been used by farmers to cool tough, damp grains to maintain a uniform temperature throughout the bin so that high moisture areas and hot spots can be delayed or prevented. The airflow for cooling grain in storage may be as low as 10% of what is used for natural-air drying. The aeration fan should run continuously as long as the outside air temperature is at least 5o cooler than the grain temperature (even during rain or periods of high humidity).
Regardless of moisture content and temperature, problems may still occur. If the grain has been stored in a “tough” condition (greater than 14.8% (feed barley), 14.5% (wheat), and 14.0% (triticale and oats)) you should examine the grain at least every two weeks by pushing your hand into the surface, as deeply as possible, and feel for warmth or crusting. Insert a long metal rod deeply into the grain to test for warmth and crusting at various depths. Feeling the rod for warmth as soon as it is withdrawn is a good indicator if you might be having grain heating and deterioration in localized parts of the bin.
As time and as the season moves forward, localized high moisture zones may develop due to changes in outdoor air temperatures. If the temperatures are low outside, the grain near the wall will cool causing a downward air flow through the grain and upward toward the centre of the bin. As the air moves through the grain it becomes warmer and begins to pick up moisture from the grain. Condensation will occur when the warm moist air hits the cool surface of the grain near the centre of the bin and can lead to grain spoilage. The reverse happens if the temperatures outside are warm. Warming on the outside of the bin from the sun causes airflow to move up and into the bin through the centre of the bin. High moisture (from condensation) will then occur at the bottom of the bin.
Drying grain carries many advantages including; extends available harvest period, allows harvesting of tough grain and therefore reduces losses from weather and wildlife, reduces or eliminates spoilage in storage, improves market grade, grain contains near maximum allowable water content which generates more dollars when sold, and may eliminate the need for swathing to get “dry” grain. Grain drying does require the extra capital for equipment, energy and operation, extra labour, and the process does require some experience to operate effectively.
The main factors to consider when handling tough grain is to continuously monitor the outside air temperature and the inside bin temperature, leave your fans run, and consider rotating your tough grain on a regular basis.