storing grain
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MOISTURE AND TEMPERATURE
Grain shelf life and ease of storage is dependent upon 2 variables. Moisture and Temperature. Think of your grain the way you think of storing food at home. The more moisture an item contains the more likely it is to spoil, so we refrigerate those items that are wet or moist to keep them from getting moldy and decomposing. As we condition grain we need to keep this shelf life chart in mind. |
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Moisture:
With wet grain our goal is to dry it first and cool it second. Fans need to run on wet grain as often as possible without overdrying. After the bin is filled and fans are turned on, a drying front develops in the grain mass and slowly works its way up until it reaches the top of the bin. Grain is like lumber in that it absorbs or desorbs moisture until it is at equilibrium with its environment.
Temperature:
For every 10 degrees we cool the grain, the storage life doubles. After we have dried *ALL* of the grain in the bin, we need to cool it to a safe storage level. Your goals for temperature should be that the average temperature of the grain in the bin is within 10 degrees of the outdoor average temperature with a minimum of 35 degrees F and a maximum of 50 degrees F. Temperature is discussed more at the bottom of this page.
With wet grain our goal is to dry it first and cool it second. Fans need to run on wet grain as often as possible without overdrying. After the bin is filled and fans are turned on, a drying front develops in the grain mass and slowly works its way up until it reaches the top of the bin. Grain is like lumber in that it absorbs or desorbs moisture until it is at equilibrium with its environment.
Temperature:
For every 10 degrees we cool the grain, the storage life doubles. After we have dried *ALL* of the grain in the bin, we need to cool it to a safe storage level. Your goals for temperature should be that the average temperature of the grain in the bin is within 10 degrees of the outdoor average temperature with a minimum of 35 degrees F and a maximum of 50 degrees F. Temperature is discussed more at the bottom of this page.
EQUILIBRIUM MOISTURE CONTENT
Equilibrium Moisture Content or EMC is an air humidity rating as it relates to grain moisture, that is derived from a given temperature and relative humidity. When EMC is known, it is an effective indicator of when fans on grain bins should be running to dry, aerate, or even moisturize various grains.
EXAMPLE: If the weather outside is 65 degrees F and the humidity is 72% Corn will equalize to 14.9% moisture. So if we could hold the weather at 65 degrees and 72% and run the fans continuously during that time, every kernel would equalize to 14.9% moisture. Kernels that are too WET would dry to 14.9 and kernels that are too DRY would re-hydrate to 14.9.
Our goal is not only to dry the grain to a level where maximum storage life is realized, but we also want to avoid over-drying because that costs money. By turning fans on and letting them run unattended we risk conditioning grain during times when the air is not conducive to drying (or too humid) and also during times when the humidity is too low and we do more drying than we intend, especially in areas of the bin where the grain is most likely already dry like the bottom portion of the bin.
EXAMPLE: If the weather outside is 65 degrees F and the humidity is 72% Corn will equalize to 14.9% moisture. So if we could hold the weather at 65 degrees and 72% and run the fans continuously during that time, every kernel would equalize to 14.9% moisture. Kernels that are too WET would dry to 14.9 and kernels that are too DRY would re-hydrate to 14.9.
Our goal is not only to dry the grain to a level where maximum storage life is realized, but we also want to avoid over-drying because that costs money. By turning fans on and letting them run unattended we risk conditioning grain during times when the air is not conducive to drying (or too humid) and also during times when the humidity is too low and we do more drying than we intend, especially in areas of the bin where the grain is most likely already dry like the bottom portion of the bin.
Fan variety and cubic feet per minute
Based on your goals with your grain and the power situation on your farm we recommend fans based on several criteria:
How wet the grain is when it is harvested, Static Pressure (which is determined by grain type), Eave height of the bin, and the Power situation on your farm (single vs. three phase).
HOW MUCH AIR DO I NEED?
If you harvest the grain in a dry state and just need to cool it down for storage, University recommendations are 1/10 CFM or 1/10 of 1 Cubic Foot per Minute per bushel of grain in the bin. This is the bare minimum. We recommend 1/5 to 1/3 CFM for safe aeration of grain. A bin with less than 1/3 CFM would be considered an aeration only bin, meaning that you could cool grain, but don't expect to do any drying.
If you are harvesting corn at 16% to 18% we would recommend you go with 1/2 to 1 CFM.
For corn that is 19% or greater, we want to see AT LEAST 1 CFM and more if possible. In most situations grain depth is the limiting factor. If your grain depth is over 20 feet it is very hard to accomplish much over 1 CFM per bushel without putting a very big fan on the bin.
For Corn that is in the 19% to 22% range we would want to see a low temp burner and an automated fan control system that would cycle the burner only when it is needed to overcome high humidity.
How wet the grain is when it is harvested, Static Pressure (which is determined by grain type), Eave height of the bin, and the Power situation on your farm (single vs. three phase).
HOW MUCH AIR DO I NEED?
If you harvest the grain in a dry state and just need to cool it down for storage, University recommendations are 1/10 CFM or 1/10 of 1 Cubic Foot per Minute per bushel of grain in the bin. This is the bare minimum. We recommend 1/5 to 1/3 CFM for safe aeration of grain. A bin with less than 1/3 CFM would be considered an aeration only bin, meaning that you could cool grain, but don't expect to do any drying.
If you are harvesting corn at 16% to 18% we would recommend you go with 1/2 to 1 CFM.
For corn that is 19% or greater, we want to see AT LEAST 1 CFM and more if possible. In most situations grain depth is the limiting factor. If your grain depth is over 20 feet it is very hard to accomplish much over 1 CFM per bushel without putting a very big fan on the bin.
For Corn that is in the 19% to 22% range we would want to see a low temp burner and an automated fan control system that would cycle the burner only when it is needed to overcome high humidity.
static pressure
Static pressure is the measure of the resistance to air flow created by bin floors, grain, and the roof of the bin. Below is an excellent demonstration video describing static pressure in the plenum of a grain bin.
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Keeping the grain depth low helps the fan to push air through the grain. Wide and short bins work better for drying and maintaining grain better than narrow and tall bins.
Small grains such as wheat and milo create a lot of static pressure due to the density of the grain mass. Small grains make it difficult for air to percolate through the spaces between kernels creating back pressure or static pressure against the fan.
Larger kernels like Corn and Soybeans don't create as much static pressure, therefore the air flows more unrestricted than with the smaller kernels.
Grain with lots of FM can also have a much higher resistance to air flow.
Small grains such as wheat and milo create a lot of static pressure due to the density of the grain mass. Small grains make it difficult for air to percolate through the spaces between kernels creating back pressure or static pressure against the fan.
Larger kernels like Corn and Soybeans don't create as much static pressure, therefore the air flows more unrestricted than with the smaller kernels.
Grain with lots of FM can also have a much higher resistance to air flow.
automated fan control
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To maximize ROI on your storage or drying bin you may consider an automated system with a weather station that takes control of the fans. Based on the settings the controller will only operate fans when the air is conducive to drying (but not over-drying) or moisturizing if you have a commodity that is too dry. Hynek Construction offers several brands and levels of temperature and moisture monitoring and automation systems that will help you get the most money for your grain. The system we most often recommend is the OPI Blue Grain Management system. Get more info here.
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grain temperature recommendations
Temperature:
In the wintertime keep grain at 35 degrees
In the Fall and Spring keep grain at about 40 degrees
In the Summertime keep grain at about 50 degrees.
Freezing grain has been a popular practice for many years, but there are a couple of drawbacks.
In the wintertime keep grain at 35 degrees
In the Fall and Spring keep grain at about 40 degrees
In the Summertime keep grain at about 50 degrees.
Freezing grain has been a popular practice for many years, but there are a couple of drawbacks.
- With grain that is going to be stored long term, you risk having condensation develop in the grain mass when the outside temperatures warm up.
- Freezing grain can cause stress cracks which affect grain quality and make it more susceptible to decay and bug activity. White corn producers are often docked for stress cracks.
- Running the fans to bring the 15 or 20 degree grain back up to a temperature that is within 10 degrees of the outside air can be a poor use of resources (time, money, fan life) considering you could have just cooled the grain to 35 which is relatively easy to do.
Moisture migration
Moisture migrations occur during warm or cold periods where the grain along the bin wall is either warmed or cooled. This causes are along the bin wall to travel to the plenum area where it is warmed causing it to rise. When the warmer air reaches the top of the bin it drops moisture on the grain at the top causing mold or spoilage. To stop a moisture migration you simply need to aerate the grain so that there is less temperature differential along the bin walls and the center grain mass.
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preventing bugs in grain
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As described above, the best way to avoid bugs is by keeping the temperature low enough to keep any bugs in the grain dormant.
Prevention: Before harvest it is a good idea to clean up the aeration floors of any leftover grain and particles. Apply a strong residual pesticide such as Malathion® or Tempo® to the aeration floors, up the bin walls, around the outside of the bin foundation and especially below and around the unloading auger. Apply the pesticide liberally. For prevention during the storage period, follow the temperature guidelines listed on this page. |
Coring | spreading | LEVELING
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CORING SPREADING AND LEVELING
For best results storing grain we need a grain mass that is uniform in shape and particle size. Several things about the way bins are filled affect grain mass shapes and air flow variability that can lead to problems. 
When a bin is filled the grain is in a peaked formation. Fine particles, foreign matter, bee’s wings etc. concentrate in the center 10’ of the bin as it is filled. When aeration fans are turned on, AIR FOLLOWS THE PATH OF LEAST RESISTANCE. In this case, that path is up the outside areas of the bin up to the vents and out. This leaves a large area of the bin that has had significantly less air flow which means it is probably wetter and warmer. Wet warm areas of the bin lead to problems like damaged grain, bugs, plugged sumps, and angry farmers.
Avoiding these problems is simple.
ii.does a good job iii.it’s relatively cheap
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