When grain is loaded into storage it is at its peak quality. Over time, the quality of the grain will only decrease; it seldom, if ever, improves. The following strategies will help maintain the quality of your grain at the same level as when it went into the bin.
Good Bin Management Suggestions
- Treat empty bins to control any stored grain pests that may be living in cracks, crevices and below the aeration floor.
- Clean any grain going into a bin.
- Remove fines and other foreign material to reduce air flow restrictions and possibly reduce the risk of spoilage.
- Core a bin (augur out some grain) after filling to establish the flow funnel and redistribute the fines, even if the removed material is put back into the same bin.
- Install a manometer in the air plenum below the aeration floor to monitor the static pressure of the air moved by the fan. For information on how to build a manometer, see Figure 11-1, Home-Built Manometer.
- Use the measured static pressure and the fan performance curve to determine the air flow delivered by the fan.
- Tightly cover unused aeration fan inlets to prevent unintentional air movement through the grain.
Why Aerate Grain in Bins
Grain bin aeration:
- Removes field heat at the time of harvest or cools grain from a dryer
- Brings the whole mass to a uniform temperature
- Removes moisture that has respired from the stored grain as a result of temperature changes caused by the outside air
As bin surfaces are warmed or cooled by the sun or outside air, air currents start to move by convection in the grain mass. Moisture from the grain is carried by these convective air cells and condenses on colder surfaces. These colder areas may be inner bin surfaces or the grain itself. Spoilage can occur if this convective air movement is not arrested. Routine aeration of the bin contents will prevent convective air movement.
Maintain a temperature differential of no more than 5°C between the grain mass and the average outside air temperature to prevent convective air movement from occurring.
Table 11-1. Time Required for Aeration Front to Move Through Grain
Basics of Aeration
- Bring the whole grain mass to the same temperature.
- Operate the fan only when relative humidity levels will not add moisture to the grain.
- Operate the fan for long enough to totally change the whole grain mass temperature – this may require a number of days. The time required for this will depend on the airflow rate per bushel.
- Become familiar with Equilibrium Moisture Content charts for the grain or beans you are storing (see the section Harvest and Storage in each commodity chapter). Run the fan only under outside conditions that will not add moisture to the stored product. Relative humidity levels of night-time air can add moisture to small grains, beans and natural air dried corn.
- See Table 11-1, Time Required for Aeration Front to Move Through Grain, for the aeration time required to completely change the bin content temperature.
Grain Storage Monitoring
Monitor all bins of grain stored on the farm on a routine schedule.
Stored grain that is used regularly for feed can be monitored as it is being used. Set up a routine for checking the bins of grains that are not being used regularly. Grain can go out of condition quickly. By carefully and diligently monitoring storage bins, growers will be able to detect the warning signs of possible spoilage problems and be able to take appropriate action to prevent further reductions in quality.
Monthly Bin Monitoring Checklist
- Turn on the aeration fan.
- Climb up and look inside the bin. Look for signs of moisture on the underside of the roof. If water droplets or ice are present, aerate the bin. Moisture from the grain has been carried into the attic space and condensed on the roof metal.
- Run the aeration fan if a light dusting of snow has been driven into the top of a storage bin. It will sublimate and be discharged as harmless water vapour. If much greater amounts of snow are found, shovel it out.
- Check for any off-odours. The air should smell like clean grain.
- Check the grain surface to see if it looks the same as the last time. If it looks dull or off-colour, investigate further.
- Check for changes in the static pressure or the working pressure of the fan in the plenum under the aeration floor since the previous month. A decrease is no cause for concern. An increase, however, indicates that something has increased the resistance of the air as it moves through the grain mass. Investigate deeper into the grain mass.
- Look for any signs of insect activity.
- Record your notes in a monitoring logbook for comparison with the next month’s readings.