Managing Grain Quality in On-farm Stored Grain

042913_2028_HaveILostAn2Now that the crop is off the field and in the bins, I have heard a lot of different opinions on proper storage of grain through the winter.  What is the ideal moisture and when and how is the proper way to cool the bin?  I did some looking and have put together the following information, if not to clarify the subject, then to add another opinion to the discussion.

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Loading the Bin

Good grain storage starts at the time of filling the bin.  The bin should be dusted with a treatment like Protect-it to help with insect control prior to filling, followed by treating the grain while filling the bin.  Grain should be cleaned as it is being off-loaded into the bin.  Controlling temperature and moisture content of the grain using aeration fans is necessary to manage grain quality during storage.  Dirt, weed seeds, fines and chaff can result in disruptions of air flow through the entire mass.  Areas of heavy concentration of these materials can be so dense that moisture and temperature cannot be altered.  Coring the bin occasionally while it is being filled can reduce the amount of fines and other foreign matter that accumulate in the center of the grain mass.

Leaving a peak of grain in the head space area and/or over-filling a bin to the point that there is no room to work, maximizes storage space but causes inefficient air movement.  Ideally, the head space of a filled bin should be level to a common depth across the entire diameter of the bin. Peaks are difficult to manage with aeration.  Air, like water, will travel the path of least resistance.  Air will more quickly exit a grain mass through the lowest edges of peaked grain leaving the center of the peaked grain not aerated.  If the bin cannot be levels, coring the bin periodically will help minimize this problem.

Temperature and Moisture

Proper drying is imperative to successful storage.  Based on the expected storage time, target moistures will vary.  Below is a list of target moistures based on projected storage times for good quality grain in aerated storage.

Maximum moisture content

Grain type & Storage time                          for safe storage, %*

Shelled corn

Shipped by spring                                                         15 1/2

Stored 6-12 month                                                        14

Stored more than 1 year                                               13

Soybeans

Sold by spring                                                                14

Stored up to 1 year                                                        12

Stored more than 1 year                                                11

*Reduce the moisture 1% below table values for poor quality grain resulting from drought, frost, blight, harvest damage, etc.

Source: C Young – Ohio State University

Aeration fans should be started as soon as the bin floor is covered with grain and operated continuously until the grain is dry or the average air temperature is below 35oF or 1-2oC for extended periods.  Leave all roof hatches open to provide a large air exhaust opening, approximately 1ft2 for each 1,000 cubic feet per minute of air delivered to the bin.

Adjusting the temperature of grain in a filled bin should be done in steps.  The movement of a temperature front (zone) completely through the grain is one cooling or warming cycle.  Each time an adjustment is made, run the aeration fans continuously until the zone moves completely through the grain before shutting down the system.  Failure to do so can lead to major problems in the grain mass wherever the front was allowed to stop.  How long that takes varies with the number and sizes (airflow rates) of aeration fans attached to a bin, as shown in Table 2.

Table 2. Approximate times for one grain cooling or warming cycle.*

Airflow Rate (cfm/bu)

Fall Cooling hours

Winter Cooling Hours

Spring Warming Hours

1/20

300

400

240

1/10

150

200

120

1/5

75

100

60

1/4

60

50

48

1/3

45

61

36

1/2

30

40

24

3/4

20

27

16

1

15

20

12

1 1/4

12

16

10

1 1/2

10

13

8

* Times are based 10-15 degree temperature changes.

Source: C Young – Ohio State University

Grain drying or rewetting is usually insignificant during grain aeration.  Because the cooling (or warming) front moves through the grain about 50 times faster than a drying or wetting front, only a small fraction of the grain is rewetted during an aeration cycle, even with high humidity.  However, as a precaution to minimize rewetting, operate the aeration fan only long enough to accomplish the grain cooling or warming cycle. This is particularly important with higher capacity aeration fans.  After cooling is completed, close the roof hatches and cover fan inlets to prevent migrating external air from adding moisture to the grain.

Regular Observations

When the daily average temperature drops below 35oF or 1-2oC, cool the grain to a uniform temperature and turn the fan off.  Check the bins on a regular basis for any sign or smell of problems. If moldy odors are detected or the grain starts to heat, turn the fan on until the conditions are corrected.  In larger bins, consider installing temperature probes to locate hot spots in the bin.

Maintaining proper grain quality is a key to maximizing return on sold grain.  Grade deductions can be as costly as production mistakes in the field.  Some basic and simple steps now can pay dividends come spring.